April 30, 2017
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Discontinued Warning IconPlease Note: This Brand Name drug is no longer available in the US.
(Generic versions may still be available.)

Side Effects


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.

Read the Ismelin (guanethidine monosulfate) Side Effects Center for a complete guide to possible side effects


Concurrent use of Ismelin (guanethidine monosulfate) and rauwolfia derivatives may cause excessive postural hypotension, bradycardia, and mental depression.

Both digitalis and Ismelin (guanethidine monosulfate) slow the heart rate.

Thiazide diuretics enhance the antihypertensive action of Ismelin (see DOSAGE AND ADMINISTRATION).

Amphetamine-like compounds, stimulants (e.g., ephedrine, methylphenidate), tricyclic antidepressants (e.g., amitriptyline, imipramine, desipramine) and other psychopharmacologic agents (e.g., phenothiazines and related compounds), as well as oral contraceptives, may reduce the hypotensive effect of Ismelin (guanethidine monosulfate) .

MAO inhibitors should be discontinued for at least 1 week before starting therapy with Ismelin (guanethidine monosulfate) . This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 12/8/2004

Side Effects

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.


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