FDA label e2e2e3bb-3e46-4329-b907-82d47cd7ff24

WARNINGS Ismelin is a potent drug and its use can lead to disturbing and serious clinical problems. Before prescribing, physicians should familiarize themselves with the details of its use and warn patients not to deviate from instructions. Orthostatic hypotension can occur frequently, and patients should be properly instructed about this potential hazard. Fainting spells may occur unless the patient is forewarned to sit or lie down with the onset of dizziness or weakness. Postural hypotension is most marked in the morning and is accentuated by hot weather, alcohol, or exercise. Dizziness or weakness may be particularly bothersome during the initial period of dosage adjustment and with postural changes, such as arising in the morning. The potential occurrence of these symptoms may require alteration of previous daily activity. The patient should be cautioned to avoid sudden or prolonged standing or exercise while taking the drug. Inhibition of ejaculation has been reported in animals (see PRECAUTIONS, Carcinogenesis, Mutagenesis, Impairment of Fertility) as well as in men given Ismelin. This effect, which results from the sympathetic blockade caused by the drug's action, is reversible after Ismelin has been discontinued for several weeks. The drug does not cause parasympathetic blockade, and erectile potency is usually retained during administration of Ismelin. The possible occurrence of inhibition of ejaculation should be kept in mind when considering the use of guanethidine in men of reproductive age. If possible, therapy should be withdrawn 2 weeks prior to surgery to reduce the possibility of vascular collapse and cardiac arrest during anesthesia. If emergency surgery is indicated, preanesthetic and anesthetic agents should be administered cautiously in reduced dosage. Oxygen, atropine, vasopressors, and adequate solutions for volume replacement should be ready for immediate use to counteract vascular collapse in the surgical patient. Vasopressors should be used only with extreme caution, since Ismelin augments responsiveness to exogenously administered norepinephrine and vasopressors; specifically, blood pressure may rise and cardiac arrhythmias may be produced.

<table> <col/> <thead> <tr> <td> Orthostatic hypotension can occur frequently, and patients should be properly instructed about this potential hazard. Fainting spells may occur unless the patient is forewarned to sit or lie down with the onset of dizziness or weakness. Postural hypotension is most marked in the morning and is accentuated by hot weather, alcohol, or exercise. Dizziness or weakness may be particularly bothersome during the initial period of dosage adjustment and with postural changes, such as arising in the morning. The potential occurrence of these symptoms may require alteration of previous daily activity. The patient should be cautioned to avoid sudden or prolonged standing or exercise while taking the drug.</td> </tr> </thead> <tbody> <tr> <td> </td> </tr> </tbody> </table>

ADVERSE REACTIONS The following adverse reactions have been observed, but there are not enough data to support an estimate of their frequency. Consequently the reactions are categorized by organ system and are listed in decreasing order of severity and not frequency. Digestive: Diarrhea, which may be severe at times and necessitate discontinuance of medication; vomiting; nausea: increased bowel movements; dry mouth: parotid tenderness. Cardiovascular: Chest pains (angina): bradycardia; a tendency toward fluid retention and edema with occasional development of congestive heart failure Respiratory: Dyspnea; asthma in susceptible individuals: nasal congestion. Neurologic : Syncope resulting from either postural or exertional hypotension; dizziness; blurred vision, muscle tremor; ptosis of the lids; mental depression; chest paresthesias; weakness; lassitude; fatigue. Muscular: Myalgia. Genitourinary: Rise in BUN; urinary incontinence; inhibition of ejaculation; nocturia. Metabolic: Weight gain. Skin and Appendages: Dermatitis; scalp hair loss. Although a causal relationship has not been established. a few instances of blood dyscrasias (anemia, thrombocytopenia, and leukopenia) and of priapism or impotence have been reported.