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adverse reactions
ADVERSE REACTIONS Mexiletine hydrochloride commonly produces reversible gastrointestinal and nervous system adverse reactions but is otherwise well tolerated. Mexiletine has been evaluated in 483 patients in one-month and three-month controlled studies and in over 10,000 patients in a large compassionate use program. Dosages in the controlled studies ranged from 600-1,200 mg/day; some patients (8%) in the compassionate use program were treated with higher daily doses (1,600-3,200 mg/day). In the three- month controlled trials comparing mexiletine to quinidine, procainamide and disopyramide, the most frequent adverse reactions were upper gastrointestinal distress (41%), lightheadedness (10.5%), tremor (12.6%) and coordination difficulties (10.2%). Similar frequency and incidence were observed in the one-month placebo-controlled trial. Although these reactions were generally not serious, and were dose-related and reversible with a reduction in dosage, by taking the drug with food or antacid or by therapy discontinuation, they led to therapy discontinuation in 40% of patients in the controlled trials. Table 1 presents the adverse events reported in the one-month placebo-controlled trial. Table 1 : Comparative Incidence (%) of Adverse Events Among Patients Treated with Mexiletine and Placebo in the 4-Week, Double-blind Crossover Trial Mexiletine N=53 Placebo N=49 Cardiovascular Palpitations 7.5 10.2 Chest Pain 7.5 4.1 Increased Ventricular Arrhythmia /PVC's 1.9 - Digestive Nausea/Vomiting/Heartburn 39.6 6.1 Central Nervous System Dizziness/Lightheadedness 26.4 14.3 Tremor 13.2 — Nervousness 11.3 6.1 Coordination Difficulties 9.4 — Changes in Sleep Habits 7.5 16.3 Paresthesias/Numbness 3.8 2.0 Weakness 1.9 4.1 Fatigue 1.9 2.0 Tinnitus 1.9 4.1 Confusion/Clouded Sensorium 1.9 2.0 Other Headache 7.5 6.1 Blurred Vision/Visual Disturbances 7.5 2.0 Dyspnea/Respiratory 5.7 10.2 Rash 3.8 2.0 Non-specific Edema 3.8 — Table 2: Comparative Incidence (%) of Adverse Events Among Patients Treated with Mexiletine or Control Drugs in the 12-Week Double-blind Trials Table 2 presents the adverse reactions occurring in one percent or more of patients in the three-month controlled studies. Mexiletine N = 430 Quinidine N = 262 Procainamide N = 78 Disopyramide N = 69 Cardiovascular Palpitations 4.3 4.6 1.3 5.8 Chest Pain 2.6 3.4 1.3 2.9 Angina/Angina-like Pain 1.7 1.9 2.6 2.9 Increased Ventricular Arrhythmias/PVC's 1.0 2.7 2.6 — Digestive Nausea/Vomiting/Heartburn 39.3 21.4 33.3 14.5 Diarrhea 5.2 33.2 2.6 8.7 Constipation 4.0 — 6.4 11.6 Changes in Appetite 2.6 1.9 — — Abdominal Pain/Cramps/Discomfort 1.2 1.5 — 1.4 Central Nervous System Dizziness/Lightheadedness 18.9 14.1 14.1 2.9 Tremor 13.2 2.3 3.8 1.4 Coordination Difficulties 9.7 1.1 1.3 — Changes in Sleep Habits 7.1 2.7 11.5 8.7 Weakness 5.0 5.3 7.7 2.9 Nervousness 5.0 1.9 6.4 5.8 Fatigue 3.8 5.7 5.1 1.4 Speech Difficulties 2.6 0.4 — — Confusion/Clouded Sensorium 2.6 — 3.8 — Paresthesias/Numbness 2.4 2.3 2.6 — Tinnitus 2.4 1.5 — — Depression 2.4 1.1 1.3 1.4 Other Blurred Vision/Visual Disturbances 5.7 3.1 5.1 7.2 Headache 5.7 6.9 7.7 4.3 Rash 4.2 3.8 10.3 1.4 Dyspnea/ Respiratory 3.3 3.1 5.1 2.9 Dry Mouth 2.8 1.9 5.1 14.5 Arthralgia 1.7 2.3 5.1 1.4 Fever 1.2 3.1 2.6 — An additional group of over 10,000 patients has been treated in a program allowing administration of mexiletine hydrochloride under compassionate use circumstances. These patients were seriously ill with the large majority on multiple drug therapy. Twenty-four percent of the patients continued in the program for one year or longer. Adverse reactions leading to therapy discontinuation occurred in 15 percent of patients (usually upper gastrointestinal system or nervous system effects). In general, the more common adverse reactions were similar to those in the controlled trials. Less common adverse events possibly related to mexiletine use include:Less than 1%: Syncope, edema, hot flashes, hypertension, short-term memory loss, loss of consciousness, other psychological changes, diaphoresis, urinary hesitancy/retention, malaise, impotence/decreased libido, pharyngitis, congestive heart failure. Cardiovascular System Syncope and hypotension, each about 6 in 1,000; bradycardia, about 4 in 1,000; angina/angina-like pain, about 3 in 1,000; edema, atrioventricular block/conduction disturbances and hot flashes, each about 2 in 1,000; atrial arrhythmias, hypertension and cardiogenic shock, each about 1 in 1,000. Central Nervous System Short-term memory loss, about 9 in 1,000 patients; hallucinations and other psychological changes, each about 3 in 1,000; psychosis and convulsions/seizures, each about 2 in 1,000; loss of consciousness, about 6 in 10,000. Digestive Dysphagia, about 2 in 1,000; peptic ulcer, about 8 in 10,000; upper gastrointestinal bleeding, about 7 in 10,000; esophageal ulceration, about 1 in 10,000. Rare cases of severe hepatitis/acute hepatic necrosis. Skin Rare cases of exfoliative dermatitis and Stevens-Johnson Syndrome with mexiletine treatment have been reported. Laboratory Abnormal liver function tests, about 5 in 1,000 patients; positive ANA and thrombocytopenia, each about 2 in 1,000; leukopenia (including neutropenia and agranulocytosis), about 1 in 1,000; myelofibrosis, about 2 in 10,000 patients. Other Diaphoresis, about 6 in 1,000; altered taste, about 5 in 1,000; salivary changes, hair loss and impotence/decreased libido, each about 4 in 1,000; malaise, about 3 in 1,000; urinary hesitancy/retention, each about 2 in 1,000; hiccups, dry skin, laryngeal and pharyngeal changes and changes in oral mucous membranes, each about 1 in 1,000; SLE syndrome, about 4 in 10,000. Hematology Blood dyscrasias were not seen in the controlled trials but did occur among 10,867 patients treated with mexiletine in the compassionate use program (see PRECAUTIONS). Myelofibrosis was reported in two patients in the compassionate use program: one was receiving long- term thiotepa therapy and the other had pretreatment myeloid abnormalities. In postmarketing experience, there have been isolated, spontaneous reports of pulmonary changes including pulmonary infiltration and pulmonary fibrosis during mexiletine therapy with or without other drugs or diseases that are known to produce pulmonary toxicity. A causal relationship to mexiletine therapy has not been established. In addition, there have been isolated reports of drowsiness, nystagmus, ataxia, dyspepsia, hypersensitivity reaction, and exacerbation of congestive heart failure in patients with pre-existing compromised ventricular function. There have been rare reports of pancreatitis associated with mexiletine treatment.