April 27, 2017
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"Dec. 18, 2012 -- People who can't get their high blood pressure down with drugs may be helped by a new procedure that deactivates overactive nerves in the kidneys, a small study shows.

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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.)

Ismelin Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Last reviewed on RxList 4/8/2016

Ismelin (guanethidine monosulfate) is an antihypertensive used to treat hypertension (high blood pressure). Ismelin is also used to treat high blood pressure in the kidneys. The brand name Ismelin is discontinued, but generic versions may be available. Common side effects of Ismelin (guanethidine monosulfate) include:

The initial adult dose of Ismelin is 10 or 12.5 milligrams (mg) once a day. Then, your doctor may increase your dose to 25 to 50 mg once a day. Ismelin may interact with monoamine oxidase inhibitors (MAOIs), haloperidol, methylphenidate, minoxidil, thiothixene, respiratory medicines, phenothiazines, or tricyclic antidepressants. Tell your doctor all medications and supplements you use. It is unknown if Ismelin will be harmful to a fetus. Tell your doctor if you are pregnant or could become pregnant during treatment. This drug passes into breast milk and may harm a nursing infant. Consult your doctor before breastfeeding.

Our Ismelin (guanethidine monosulfate) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Ismelin FDA Prescribing Information: Side Effects
(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.

Read the entire FDA prescribing information for Ismelin (Guanethidine Monosulfate)

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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