Morphine Sulfate

Initiate the dosing regimen for each patient individually, taking into account the patient's prior analgesic treatment experience. Monitor patients closely for respiratory depression, especially within the first 24 to 72 hours of initiating therapy with morphine sulfate extended-release tablets [see Warnings and Precautions ( 5.2 )].

Consider the following factors when selecting an initial dose of morphine sulfate extended-release tablets:

• Total daily dose, potency, and any prior opioid the patient has been taking previously;
• Reliability of the relative potency estimate used to calculate the equivalent dose of morphine needed (Note: potency estimates may vary with the route of administration);
• Patient's degree of opioid experience and opioid tolerance;
• General condition and medical status of the patient;
• Concurrent medication;
• Type and severity of the patient's pain.

Morphine sulfate extended-release tablets are administered at a frequency of twice daily (every 12 hours) or three times daily (every 8 hours).

Use of Morphine Sulfate Extended-Release Tablets as the First Opioid Analgesic

There has been no systematic evaluation of morphine sulfate extended-release tablets as an initial opioid analgesic in the management of pain.  Because it may be more difficult to titrate a patient using controlled-release morphine, it is ordinarily advisable to begin treatment using an immediate-release formulation.

Conversion from Other Oral Morphine to Morphine Sulfate Extended-Release Tablets

Patients receiving other oral morphine formulations may be converted to morphine sulfate extended-release tablets by administering one-half of the patient's 24-hour requirement as morphine sulfate extended-release tablets on an every-12-hour schedule or by administering one-third of the patient's daily requirement as morphine sulfate extended-release tablets on an every-8-hour schedule.

Conversion from Parenteral Morphine or Other Opioids (Parenteral or Oral) to Morphine Sulfate Extended-Release Tablets

While there are useful tables of oral and parenteral equivalents, there is substantial inter-patient variability in the relative potency of different opioid drugs and formulations. As such, it is safer to underestimate a patient’s 24-hour oral morphine dose and provide rescue medication (e.g., immediate-release morphine) than to overestimate the 24-hour oral morphine dose and manage an adverse reaction.  Consider the following general points:

• Parenteral to oral morphine ratio: Between 2 to 6 mg of oral morphine may be required to provide analgesia equivalent to 1 mg of parenteral morphine. Typically, a dose of morphine that is approximately three times the previous daily parenteral morphine requirement is sufficient.

• Other parenteral or oral non-morphine opioids to oral morphine sulfate: Specific recommendations are not available because of a lack of systematic evidence for these types of analgesic substitutions. Published relative potency data are available, but such ratios are approximations. In general, begin with half of the estimated daily morphine requirement as the initial dose, managing inadequate analgesia by supplementation with immediate-release morphine.

The first dose of morphine sulfate extended-release tablets may be taken with the last dose of any immediate-release opioid medication due to the extended-release characteristics of the morphine sulfate extended-release tablets formulation.

Individually titrate morphine sulfate extended-release tablets to a dose that provides adequate analgesia and minimizes adverse reactions.  Continually reevaluate patients receiving morphine sulfate extended-release tablets to assess the maintenance of pain control and the relative incidence of adverse reactions.  During chronic therapy, especially for non-cancer-related pain (or pain associated with other terminal illnesses), periodically reassess the continued need for the use of opioid analgesics.

If the level of pain increases, attempt to identify the source of increased pain, while adjusting the morphine sulfate extended-release tablets dose to decrease the level of pain.  Because steady-state plasma concentrations are approximated in 1 day, morphine sulfate extended-release tablets dosage adjustments may be done every 1 to 2 days.  Patients who experience breakthrough pain may require dosage adjustment or rescue medication with an appropriate dose of an immediate-release opioid and non-opioid medication.

If signs of excessive opioid-related adverse reactions are observed, the next dose may be reduced.  Adjust the dose to obtain an appropriate balance between management of pain and opioid-related adverse reactions.

During chronic, around-the-clock opioid therapy, especially for non-cancer pain syndromes, the continued need for around-the-clock opioid therapy should be reassessed periodically (e.g., every 6 to 12 months) as appropriate.

When the patient no longer requires therapy with morphine sulfate extended-release tablets, use a gradual downward titration of the dose to prevent signs and symptoms of withdrawal in the physically-dependent patient.  Do not abruptly discontinue morphine sulfate extended-release tablets.

Instruct patients to swallow morphine sulfate extended-release tablets intact. The tablets are not to be crushed, dissolved, or chewed due to the risk of rapid release and absorption of a potentially fatal dose of morphine [see Warnings and Precautions ( 5.2 )].

Morphine sulfate extended-release tablets contain morphine, an opioid agonist and a Schedule II controlled substance.  Morphine can be abused in a manner similar to other opioid agonists, legal or illicit.  Opioid agonists are sought by drug abusers and people with addiction disorders and are subject to criminal diversion.  Consider these risks when prescribing or dispensing morphine sulfate extended-release tablets in situations where there is concern about increased risks of misuse, abuse, or diversion.  Concerns about abuse, addiction, and diversion should not, however, prevent the proper management of pain.

Assess each patient’s risk for opioid abuse or addiction prior to prescribing morphine sulfate extended-release tablets.  The risk for opioid abuse is increased in patients with a personal or family history of substance abuse (including drug or alcohol abuse or addiction) or mental illness (e.g., major depression).  Patients at increased risk may still be appropriately treated with modified-release opioid formulations; however these patients will require intensive monitoring for signs of misuse, abuse, or addiction. Routinely monitor all patients receiving opioids for signs of misuse, abuse, and addiction because these drugs carry a risk for addiction even under appropriate medical use.

Misuse or abuse of morphine sulfate extended-release tablets by crushing, chewing, snorting, or injecting the dissolved product will result in the uncontrolled delivery of the opioid and pose a significant risk that could result in overdose and death [see  Overdosage ( 10 )].

Contact local state professional licensing board or state controlled substances authority for information on how to prevent and detect abuse or diversion of this product.

Respiratory depression is the chief hazard of opioid agonists, including morphine sulfate extended-release tablets.  Respiratory depression if not immediately recognized and treated, may lead to respiratory arrest and death.  Respiratory depression from opioids is manifested by a reduced urge to breathe and a decreased rate of respiration, often associated with a “sighing” pattern of breathing (deep breaths separated by abnormally long pauses). Carbon dioxide (CO₂) retention from opioid-induced respiratory depression can exacerbate the sedating effects of opioids.  Management of respiratory depression may include close observation, supportive measures, and use of opioid antagonists, depending on the patient’s clinical status [see Overdosage ( 10 )].

While serious, life-threatening, or fatal respiratory depression can occur at any time during the use of morphine sulfate extended-release tablets, the risk is greatest during the initiation of therapy or following a dose increase. Closely monitor patients for respiratory depression when initiating therapy with morphine sulfate extended-release tablets and following dose increases.  Instruct patients against use by individuals other than the patient for whom morphine sulfate extended-release tablets were prescribed and to keep morphine sulfate extended-release tablets out of the reach of children, as such inappropriate use may result in fatal respiratory depression.

To reduce the risk of respiratory depression, proper dosing and titration of morphine sulfate extended-release tablets are essential [see Dosage and Administration ( 2 )]. Overestimating the morphine sulfate extended-release tablets dose when converting patients from another opioid product can result in fatal overdose with the first dose.  Respiratory depression has also been reported with use of modified-release opioids when used as recommended and not misused or abused.

To further reduce the risk of respiratory depression, consider the following:

• Proper dosing and titration are essential and morphine sulfate extended-release tablets should only be prescribed by healthcare professionals who are knowledgeable in the use of potent opioids for the management of chronic pain. Morphine sulfate extended-release 100 mg and 200 mg tablets are for use in opioid-tolerant patients only. Ingestion of these strengths of morphine sulfate extended-release tablets may cause fatal respiratory depression when administered to patients not already tolerant to high doses of opioids.
• Instruct patients to swallow morphine sulfate extended-release tablets intact.  The tablets are not to be crushed, dissolved, or chewed. The resulting morphine dose may be fatal, particularly in opioid-naïve individuals.
• Morphine sulfate extended-release tablets are contraindicated in patients with respiratory depression and in patients with conditions that increase the risk of life-threatening respiratory depression [see Contraindications (4)].

Accidental consumption of morphine sulfate extended-release tablets, especially in children, can result in a fatal overdose of morphine.

Respiratory depression is more likely to occur in elderly, cachectic, or debilitated patients as they may have altered pharmacokinetics or altered clearance compared to younger, healthier patients. Therefore, monitor such patients closely, particularly when initiating and titrating morphine sulfate extended-release tablets and when morphine sulfate extended-release tablets are given concomitantly with other drugs that depress respiration [see Warnings and Precautions ( 5.2 )].

Monitor patients with significant chronic obstructive pulmonary disease or cor pulmonale, and patients having a substantially decreased respiratory reserve, hypoxia, hypercapnia, or pre-existing respiratory depression for respiratory depression, particularly when initiating therapy and titrating with morphine sulfate extended-release tablets, as in these patients, even usual therapeutic doses of morphine sulfate extended-release tablets may decrease respiratory drive to the point of apnea [see Warnings and Precautions ( 5.2 )].  Consider the use of alternative non-opioid analgesics in these patients if possible.

Hypotension, and profound sedation, coma or respiratory depression may result if morphine sulfate extended-release tablets are used concomitantly with other CNS depressants (e.g., sedatives, anxiolytics, hypnotics, neuroleptics, muscle relaxants, other opioids). When considering the use of morphine sulfate extended-release tablets in a patient taking a CNS depressant, assess the duration of use of the CNS depressant and the patient’s response, including the degree of tolerance that has developed to CNS depression.  Additionally, consider the patient’s use, if any, of alcohol and/or illicit drugs that can cause CNS depression. If  morphine sulfate extended-release tablet therapy is to be initiated in a patient taking a CNS depressant, start with a lower morphine sulfate extended-release tablet dose than usual and monitor patients for signs of sedation and respiratory depression and consider using a lower dose of the concomitant CNS depressant [see Drug Interactions ( 7.1 )].

Morphine sulfate extended-release tablets may cause severe hypotension including orthostatic hypotension and syncope in ambulatory patients. There is an increased risk in patients whose ability to maintain blood pressure has already been compromised by a reduced blood volume or concurrent administration of certain CNS depressant drugs (e.g., phenothiazines or general anesthetics) [see Drug Interactions ( 7.1 )].  Monitor these patients for signs of hypotension after initiating or titrating the dose of morphine sulfate extended-release tablets. In patients with circulatory shock, morphine sulfate extended-release tablets may cause vasodilation that can further reduce cardiac output and blood pressure. Avoid the use of morphine sulfate extended-release tablets in patients with circulatory shock.

Monitor patients taking morphine sulfate extended-release tablets that may be susceptible to the intracranial effects of CO₂ retention (e.g., those with evidence of increased intracranial pressure or brain tumors) for signs of sedation and respiratory depression, particularly when initiating therapy with morphine sulfate extended-release tablets.  Morphine sulfate extended-release tablets may reduce respiratory drive, and the resultant CO₂ retention can further increase intracranial pressure. Opioids may also obscure the clinical course in a patient with a head injury.

Avoid the use of morphine sulfate extended-release tablets in patients with impaired consciousness or coma.

Morphine sulfate extended-release tablets are contraindicated in patients with paralytic ileus.  Avoid the use of morphine sulfate extended-release tablets in patients with other GI obstruction.

The morphine in morphine sulfate extended-release tablets may cause spasm of the sphincter of Oddi.  Monitor patients with biliary tract disease, including acute pancreatitis, for worsening symptoms.  Opioids may cause increases in the serum amylase.

The morphine in morphine sulfate extended-release tablets may aggravate convulsions in patients with convulsive disorders, and may induce or aggravate seizures in some clinical settings.  Monitor patients with a history of seizure disorders for worsened seizure control during morphine sulfate extended-release tablet therapy.

Avoid the use of mixed agonist/antagonist analgesics (i.e., pentazocine, nalbuphine, and butorphanol) in patients who have received or are receiving a course of therapy with a full opioid agonist analgesic, including morphine sulfate extended-release tablets.  In these patients, mixed agonists/antagonists analgesics may reduce the analgesic effect and/or may precipitate withdrawal symptoms.

When discontinuing morphine sulfate extended-release tablets, gradually taper the dose [see Dosage and Administration ( 2.3 )]. Do not abruptly discontinue morphine sulfate extended-release tablets.

Morphine sulfate extended-release tablets may impair the mental or physical abilities needed to perform potentially hazardous activities such as driving a car or operating machinery.  Warn patients not to drive or operate dangerous machinery unless they are tolerant to the effects of morphine sulfate extended-release tablets and know how they will react to the medication.

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Morphine sulfate extended-release tablets may increase the risk of serious adverse reactions such as those observed with other opioid analgesics, including respiratory depression, apnea, respiratory arrest, circulatory depression, hypotension, or shock [see Overdosage ( 10 )].

Most Frequently Observed Reactions

In clinical trials, the most common adverse reactions with morphine sulfate extended-release tablets were constipation, dizziness, sedation, nausea, vomiting, sweating, dysphoria, and euphoric mood.

Some of these effects seem to be more prominent in ambulatory patients and in those not experiencing severe pain.

Less Frequently Observed Reactions

Cardiovascular disorders:  tachycardia, bradycardia, palpitations

Eye disorders:  visual impairment, vision blurred, diplopia, miosis

Gastrointestinal disorders:  dry mouth, diarrhea, abdominal pain, constipation, dyspepsia

General disorders and administration site conditions:  chills, feeling abnormal, edema, edema peripheral, weakness

Hepatobiliary disorders:  biliary colic

Metabolism and nutrition disorders: anorexia

Musculoskeletal and connective tissue disorders:  muscle rigidity, muscle twitching

Nervous system disorders:  presyncope, syncope, headache, tremor, uncoordinated muscle movements, convulsion, intracranial pressure increased, taste alteration, paresthesia, nystagmus

Psychiatric disorders:   agitation, mood altered, anxiety, depression, abnormal dreams, hallucination, disorientation, insomnia

Renal and urinary disorders:  urinary retention, urinary hesitation, antidiuretic effects

Reproductive system and breast disorders: reduced libido and/or potency

Respiratory, thoracic and mediastinal disorders:  laryngospasm

Skin and subcutaneous tissue disorders:  pruritus, urticaria, rash

Vascular disorders:  flushing, hypotension, hypertension

The following adverse reactions have been identified during postapproval use of morphine sulfate extended-release tablets: amenorrhea, asthenia, bronchospasm, confusional state, drug hypersensitivity, fatigue, hyperalgesia, hypertonia, ileus, increased hepatic enzymes, intestinal obstruction, lethargy, malaise, pulmonary edema, thinking disturbances, somnolence, and vertigo.   

Anaphylaxis has been reported with ingredients contained in morphine sulfate extended-release tablets. Advise patients how to recognize such a reaction and when to seek medical attention.

Concurrent use of morphine sulfate extended-release tablets and other central nervous system (CNS) depressants including sedatives or hypnotics, general anesthetics, phenothiazines, tranquilizers, and alcohol can increase the risk of respiratory depression, hypotension, profound sedation or coma.  Monitor patients receiving CNS depressants and morphine sulfate extended-release tablets for signs of respiratory depression and hypotension.  When such combined therapy is contemplated, reduce the initial dose of one or both agents.

Mixed agonist/antagonist analgesics (i.e., pentazocine, nalbuphine, butorphanol) may reduce the analgesic effect of morphine sulfate extended-release tablets or may precipitate withdrawal symptoms in these patients.  Avoid the use of agonist/antagonist analgesics in patients receiving morphine sulfate extended-release tablets.

Morphine may enhance the neuromuscular blocking action of skeletal muscle relaxants and produce an increased degree of respiratory depression.  Monitor patients receiving muscle relaxants and morphine sulfate extended-release tablets for signs of respiratory depression that may be greater than otherwise expected.

The effects of morphine may be potentiated by MAOIs.  Monitor patients on concurrent therapy with an MAOI and morphine sulfate extended-release tablets for increased respiratory and central nervous system depression. MAOIs have been reported to potentiate the effects of morphine anxiety, confusion, and significant depression of respiration or coma. Morphine sulfate extended-release tablets should not be used in patients taking MAOIs or within 14 days of stopping such treatment.

Cimetidine can potentiate morphine-induced respiratory depression. There is a report of confusion and severe respiratory depression when a patient undergoing hemodialysis was concurrently administered morphine and cimetidine.  Monitor patients for respiratory depression when morphine sulfate extended-release tablets and cimetidine are used concurrently.

Morphine can reduce the efficacy of diuretics by inducing the release of antidiuretic hormone. Morphine may also lead to acute retention of urine by causing spasm of the sphincter of the bladder, particularly in men with enlarged prostates.

Anticholinergics or other medications with anticholinergic activity when used concurrently with opioid analgesics may result in increased risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Monitor patients for signs of urinary retention or reduced gastric motility when morphine sulfate extended-release tablets are used concurrently with anticholinergic drugs.

PGP-inhibitors (e.g., quinidine) may increase the absorption/exposure of morphine sulfate by about two-fold. Therefore, monitor patients for signs of respiratory and central nervous system depression when morphine sulfate extended-release tablets are used concurrently with PGP inhibitors.

Teratogenic Effects (Pregnancy Category C)

No formal studies to assess the teratogenic effects of morphine in animals have been conducted.  It is also not known whether morphine can cause fetal harm when administered to a pregnant woman or can affect reproductive capacity.  Morphine should be given to a pregnant woman only if clearly needed.

In humans, the frequency of congenital anomalies has been reported to be no greater than expected among the children of 70 women who were treated with morphine during the first four months of pregnancy or in 448 women treated with morphine anytime during pregnancy.  Furthermore, no malformations were observed in the infant of a woman who attempted suicide by taking an overdose of morphine and other medication during the first trimester of pregnancy.

Several literature reports indicate that morphine administered subcutaneously during the early gestational period in mice and hamsters produced neurological, soft tissue and skeletal abnormalities. With one exception, the effects that have been reported were following doses that were maternally toxic and the abnormalities noted were characteristic of those observed when maternal toxicity is present.  In one study, following subcutaneous infusion of doses greater than or equal to 0.15 mg/kg to mice, exencephaly, hydronephrosis, intestinal hemorrhage, split supraoccipital, malformed sternebrae, and malformed xiphoid were noted in the absence of maternal toxicity.  In the hamster, morphine sulfate given subcutaneously on gestation day 8 produced exencephaly and cranioschisis.  In rats treated with subcutaneous infusions of morphine during the period of organogenesis, no teratogenicity was observed.  No maternal toxicity was observed in this study; however, increased mortality and growth retardation were seen in the offspring.  In two studies performed in the rabbit, no evidence of teratogenicity was reported at subcutaneous doses up to 100 mg/kg.

Non-Teratogenic Effects

Infants born to mothers who have taken opioids chronically may exhibit neonatal withdrawal syndrome [see Use in Specific Populations ( 8.6 )], reversible reduction in brain volume, small size, decreased ventilatory response to CO₂ and increased risk of sudden infant death syndrome. Morphine sulfate should be used by a pregnant woman only if the need for opioid analgesia clearly outweighs the potential risks to the fetus.

Controlled studies of chronic in utero morphine exposure in pregnant women have not been conducted.  Published literature has reported that exposure to morphine during pregnancy in animals is associated with reduction in growth and a host of behavioral abnormalities in the offspring.  Morphine treatment during gestational periods of organogenesis in rats, hamsters, guinea pigs and rabbits resulted in the following treatment-related embryotoxicity and neonatal toxicity in one or more studies: decreased litter size, embryo-fetal viability, fetal and neonatal body weights, absolute brain and cerebellar weights, delayed motor and sexual maturation, and increased neonatal mortality, cyanosis and hypothermia.  Decreased fertility in female offspring, and decreased plasma and testicular levels of luteinizing hormone and testosterone, decreased testes weights, seminiferous tubule shrinkage, germinal cell aplasia, and decreased spermatogenesis in male offspring were also observed.  Decreased litter size and viability were observed in the offspring of male rats administered morphine (25 mg/kg, IP) for 1 day prior to mating.  Behavioral abnormalities resulting from chronic morphine exposure of fetal animals included altered reflex and motor skill development, mild withdrawal, and altered responsiveness to morphine persisting into adulthood.

Opioids cross the placenta and may produce respiratory depression and psycho-physiologic effects in neonates. Morphine sulfate extended-release tablets are not recommended for use in women during and immediately prior to labor.  Occasionally, opioid analgesics may prolong labor through actions which temporarily reduce the strength, duration, and frequency of uterine contractions.  However, this effect is not consistent and may be offset by an increased rate of cervical dilatation which tends to shorten labor.

Closely observe neonates whose mothers received opioid analgesics during labor for signs of respiratory depression.  An opioid antagonist, naloxone, should be available for reversal of opioid-induced respiratory depression in the neonate in such situations.

Morphine is excreted in breast milk, with a milk to plasma morphine AUC ratio of approximately 2.5:1. The amount of morphine received by the infant varies depending on the maternal plasma concentration, the amount of milk ingested by the infant, and the extent of first pass metabolism.

Withdrawal signs can occur in breast-feeding infants when maternal administration of morphine is stopped.

Because of the potential for adverse reactions in nursing infants from morphine sulfate extended-release tablets, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.

The safety and effectiveness in pediatric patients below the age of 18 have not been established.

The pharmacokinetics of morphine sulfate extended-release tablets has not been studied in elderly patients.  Clinical studies of morphine sulfate extended-release tablets did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects.  In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

Chronic maternal use of morphine during pregnancy can affect the fetus with subsequent withdrawal signs.  Neonatal withdrawal syndrome presents as irritability, hyperactivity and abnormal sleep pattern, high pitched cry, tremor, vomiting, diarrhea and failure to gain weight.  The onset, duration and severity of neonatal withdrawal syndrome vary based on the drug used, duration of use, the dose of last maternal use, and rate of elimination of the drug by the newborn.  Neonatal opioid withdrawal syndrome, unlike opioid withdrawal syndrome in adults, may be life-threatening and should be treated according to protocols developed by neonatology experts.

Morphine sulfate extended-release tablets contain morphine, a Schedule II controlled substance with a high potential for abuse similar to other opioids including fentanyl, hydromorphone, methadone, oxycodone, and oxymorphone.  Morphine sulfate extended-release tablets can be abused and are subject to misuse, addiction, and criminal diversion [see Warnings and Precautions ( 5.1 )].

The high drug content in extended-release formulations adds to the risk of adverse outcomes from abuse and misuse.

All patients treated with opioids require careful monitoring for signs of abuse and addiction, since use of opioid analgesic products carries the risk of addiction even under appropriate medical use. Drug abuse is the intentional non-therapeutic use of an over-the-counter or prescription drug, even once, for its rewarding psychological or physiological effects.  Drug abuse includes, but is not limited to the following examples: the use of a prescription or over-the-counter drug to get “high”, or the use of steroids for performance enhancement and muscle build up.

Drug addiction is a cluster of behavioral, cognitive, and physiological phenomena that develop after repeated substance use and include: a strong desire to take the drug, difficulties in controlling its use, persisting in its use despite harmful consequences, a higher priority given to drug use than to other activities and obligations, increased tolerance , and sometimes a physical withdrawal.

"Drug seeking" behavior is very common to addicts and drug abusers. Drug-seeking tactics include emergency calls or visits near the end of office hours, refusal to undergo appropriate examination, testing or referral, repeated claims of loss of prescriptions, tampering with prescriptions and reluctance to provide prior medical records or contact information for other treating physician(s). “Doctor shopping” (visiting multiple prescribers) to obtain additional prescriptions is common among drug abusers and people suffering from untreated addiction.

Preoccupation with achieving adequate pain relief can be appropriate behavior in a patient with poor pain control.

Abuse and addiction are separate and distinct from physical dependence and tolerance. Physicians should be aware that addiction may not be accompanied by concurrent tolerance and symptoms of physical dependence in all addicts. In addition, abuse of opioids can occur in the absence of true addiction.

Morphine sulfate extended-release tablets, like other opioids, can be diverted for non-medical use into illicit channels of distribution. Careful recordkeeping of prescribing information, including quantity, frequency, and renewal requests as required by state law, is strongly advised.

Proper assessment of the patient, proper prescribing practices, periodic reevaluation of therapy, and proper dispensing and storage are appropriate measures that help to reduce abuse of opioid drugs.

Risks Specific to Abuse of Morphine Sulfate Extended-Release Tablets

Morphine sulfate extended-release tablets are for oral use only. Abuse of morphine sulfate extended-release tablets poses a risk of overdose and death. This risk is increased with concurrent abuse of morphine sulfate extended-release tablets with alcohol and other substances.  Taking cut, broken, chewed, crushed, or morphine sulfate extended-release tablets enhance drug release and increases the risk of overdose and death.

Due to the presence of talc as one of the excipients in morphine sulfate extended-release tablets, parenteral abuse can be expected to result in local tissue necrosis, infection, pulmonary granulomas, and increased risk of endocarditis and valvular heart injury. Parenteral drug abuse is commonly associated with transmission of infectious diseases such as hepatitis and HIV.

Both tolerance and physical dependence can develop during chronic opioid therapy. Tolerance is the need for increasing doses of opioids to maintain a defined effect such as analgesia (in the absence of disease progression or other external factors).  Tolerance may occur to both the desired and undesired effects of drugs, and may develop at different rates for different effects.

Physical dependence results in withdrawal symptoms after abrupt discontinuation or a significant dose reduction of a drug.  Withdrawal also may be precipitated through the administration of drugs with opioid antagonist activity, e.g., naloxone, nalmefene, or mixed agonist/antagonist analgesics (pentazocine, butorphanol, nalbuphine). Physical dependence may not occur to a clinically significant degree until after several days to weeks of continued opioid usage.

Morphine sulfate extended-release tablets should not be abruptly discontinued [see Dosage and Administration ( 2.3 )].  If morphine sulfate extended-release tablets are abruptly discontinued in a physically-dependent patient, an abstinence syndrome may occur. Some or all of the following can characterize this syndrome: restlessness, lacrimation, rhinorrhea, yawning, perspiration, chills, myalgia, and mydriasis. Other signs and symptoms also may develop, including: irritability, anxiety, backache, joint pain, weakness, abdominal cramps, insomnia, nausea, anorexia, vomiting, diarrhea, or increased blood pressure, respiratory rate, or heart rate.

Infants born to mothers physically dependent on opioids will also be physically dependent and may exhibit respiratory difficulties and withdrawal signs [see Use in Specific Populations ( 8.6 )].

Morphine sulfate, an opioid agonist, is relatively selective for the mu receptor, although it can interact with other opioid receptors at higher doses. In addition to analgesia, the widely diverse effects of morphine sulfate include analgesia, dysphoria, euphoria, somnolence, respiratory depression, diminished gastrointestinal motility, altered circulatory dynamics, histamine release, physical dependence, and alterations of the endocrine and autonomic nervous systems.

Morphine produces both its therapeutic and its adverse effects by interaction with one or more classes of specific opioid receptors located throughout the body. Morphine acts as a full agonist, binding with and activating opioid receptors at sites in the peri-aqueductal and peri-ventricular grey matter, the ventro-medial medulla and the spinal cord to produce analgesia.

Effects on the Central Nervous System

The principal actions of therapeutic value of morphine are analgesia and sedation. Specific CNS opiate receptors for endogenous compounds with opioid-like activity have been identified throughout the brain and spinal cord and are likely to play a role in the expression of analgesic effects.

Morphine produces respiratory depression by direct action on brainstem respiratory centers.  The mechanism of respiratory depression involves a reduction in the responsiveness of the brainstem respiratory centers to increases in carbon dioxide tension, and to electrical stimulation.

Morphine depresses the cough reflex by direct effect on the cough center in the medulla.  Morphine causes miosis, even in total darkness.  Pinpoint pupils are a sign of narcotic overdose but are not pathognomonic (e.g., pontine lesions of hemorrhagic or ischemic origins may produce similar findings).  Marked mydriasis rather than miosis may be seen with worsening hypoxia.

Effects on the Gastrointestinal Tract and Other Smooth Muscle

Morphine causes a reduction in motility associated with an increase in smooth muscle tone in the antrum of the stomach and in the duodenum.  Digestion of food is delayed in the small intestine and propulsive contractions are decreased.  Propulsive peristaltic waves in the colon are decreased, while tone may be increased to the point of spasm.  The end result is constipation.  Morphine can cause a marked reduction in gastric, biliary and pancreatic secretions, spasm of the sphincter of Oddi, and transient elevations in serum amylase.

Effects on the Cardiovascular System

Morphine produces peripheral vasodilation which may result in orthostatic hypotension.  Release of histamine can occur and may contribute to opioid-induced hypotension.  Manifestations of histamine release and/or peripheral vasodilation may include pruritus, flushing, red eyes, and sweating.

Effects on the Endocrine System

Opioids inhibit the secretion of ACTH, cortisol, testosterone, and luteinizing hormone (LH) in humans.  They also stimulate prolactin, growth hormone (GH) secretion, and pancreatic secretion of insulin and glucagon.

Effects on the Immune System

Opioids have been shown to have a variety of effects on components of the immune system in in vitro and animal models.  The clinical significance of these findings is unknown.  Overall, the effects of opioids appear to be modestly immunosuppressive.

Plasma Level-Analgesia Relationships

While plasma morphine-efficacy relationships can be demonstrated in non-tolerant individuals, they are influenced by a wide variety of factors and are not generally useful as a guide to the clinical use of morphine.  Dosages of morphine should be chosen and must be titrated on the basis of clinical evaluation of the patient and the balance between therapeutic and adverse effects.

CNS Depressant/Alcohol Interaction

Additive pharmacodynamic effects may be expected when morphine sulfate extended-release tablets are used in conjunction with alcohol, other opioids, or illicit drugs that cause central nervous system depression.

Morphine sulfate extended-release tablets are a controlled-release tablet containing morphine sulfate. Morphine is released from morphine sulfate extended-release tablets somewhat more slowly than from immediate-release oral preparations.  Following oral administration of a given dose of morphine, the amount ultimately absorbed is essentially the same whether the source is morphine sulfate extended-release tablets or an immediate-release formulation.  Because of pre-systemic elimination (i.e., metabolism in the gut wall and liver) only about 40% of the administered dose reaches the central compartment.

Absorption

The oral bioavailability of morphine is approximately 20 to 40%.  When morphine sulfate extended-release tablets are given on a fixed dosing regimen, steady-state is achieved in about a day.

Food Effect

The effect of food upon the systemic bioavailability of morphine sulfate extended-release tablets has not been systematically evaluated for all strengths.  One study, conducted with the 30 mg morphine sulfate extended-release tablets, showed no significant differences in C_max and AUC _(0-24h) values, whether the tablet was taken while fasting or with a high-fat breakfast.

Distribution

Once absorbed, morphine is distributed to skeletal muscle, kidneys, liver, intestinal tract, lungs, spleen, and brain.  Morphine also crosses placental membranes and has been found in breast milk. The volume of distribution (Vd) for morphine is approximately 3 to 4 liters per kilogram and morphine is 30 to 35% reversibly bound to plasma proteins.

Metabolism

The major pathways of morphine metabolism include glucuronidation to produce metabolites including morphine-3-glucuronide, M3G (about 50%) and morphine-6-glucuronide, M6G (about 5 to 15%) and sulfation in the liver to produce morphine-3-etheral sulfate. A small fraction (less than 5%) of morphine is demethylated.   M6G has been shown to have analgesic activity but crosses the blood-brain barrier poorly, while M3G has no significant analgesic activity.

Excretion

The elimination of morphine occurs primarily as renal excretion of M3G and its effective half-life after intravenous administration is normally 2 to 4 hours.  Approximately 10% of the dose is excreted unchanged in urine. In some studies involving longer periods of plasma sampling, a longer terminal half-life of about 15 hours was reported.  A small amount of the glucuronide conjugate is excreted in the bile, and there is some minor enterohepatic recycling.

Special Populations

Geriatric Patients

The pharmacokinetics of morphine sulfate extended-release tablets have not been studied in elderly patients.

Pediatric Patients

The pharmacokinetics of morphine sulfate extended-release tablets has not been studied in pediatric patients below the age of 18.

Gender

A gender analysis of pharmacokinetic data from healthy subjects taking morphine sulfate extended-release tablets indicated that morphine concentrations were similar in males and females.

Race

Chinese subjects given intravenous morphine had a higher clearance when compared to Caucasian subjects (1852 +/- 116 mL/min compared to 1495 +/- 80 mL/min).

Hepatic Impairment

Morphine pharmacokinetics are altered in individuals with cirrhosis. Clearance was found to decrease with a corresponding increase in half-life. The M3G and M6G to morphine plasma AUC ratios also decreased in these subjects, indicating diminished metabolic activity.  Adequate studies of the pharmacokinetics of morphine in patients with severe hepatic impairment have not been conducted.

Renal Impairment

Morphine pharmacokinetics are altered in patients with renal failure. The AUC is increased and clearance is decreased and the metabolites, M3G and M6G, may accumulate to much higher plasma levels in patients with renal failure as compared to patients with normal renal function. Adequate studies of the pharmacokinetics of morphine in patients with severe renal impairment have not been conducted.

Carcinogenesis:   Studies in animals to evaluate the carcinogenic potential of morphine have not been conducted.

Mutagenesis:  No formal studies to assess the mutagenic potential of morphine have been conducted.  In the published literature, morphine was found to be mutagenic in vitro increasing DNA fragmentation in human T-cells.  Morphine was reported to be mutagenic in the in vivo mouse micronucleus assay and positive for the induction of chromosomal aberrations in mouse spermatids and murine lymphocytes.  Mechanistic studies suggest that the in vivo clastogenic effects reported with morphine in mice may be related to increases in glucocorticoid levels produced by morphine in this species.  In contrast to the above positive findings, in vitro studies in the literature have also shown that morphine did not induce chromosomal aberrations in human leukocytes or translocations or lethal mutations in Drosophila.

Impairment of Fertility: No formal nonclinical studies to assess the potential of morphine to impair fertility have been conducted.  Several nonclinical studies from the literature have demonstrated adverse effects on male fertility in the rat from exposure to morphine.  One study in which male rats were administered morphine sulfate subcutaneously prior to mating (up to 30 mg/kg twice daily) and during mating (20 mg/kg twice daily) with untreated females, a number of adverse reproductive effects including reduction in total pregnancies, higher incidence of pseudopregnancies, and reduction in implantation sites were seen.  Studies from the literature have also reported changes in hormonal levels (i.e., testosterone, luteinizing hormone, serum corticosterone) following treatment with morphine.  These changes may be associated with the reported effects on fertility in the rat.