April 26, 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.)

How Supplied


Ismelin (guanethidine monosulfate) is indicated for the treatment of moderate and severe hypertension, either alone or as an adjunct, and for the treatment of renal hypertension, including that secondary to pyelonephritis, renal amyloidosis, and renal artery stenosis.

High blood pressure can cause the heart and arteries to not function properly. This can damage the blood vessels of the brain, heart, and kidneys, resulting in a stroke, heart failure, or kidney failure. High blood pressure may also increase the risk of heart attacks. These problems may be less likely to occur if blood pressure is controlled.


Better control may be obtained, especially in the initial phases of treatment, if the patient can have his blood pressure recorded regularly at home.

Adults- At first, 10 or 12.5 milligrams (mg) once a day. Then, your doctor may increase your dose to 25 to 50 mg once a day.

Children-The dose is based on body weight and must be determined by your doctor. The usual dose is 200 micrograms (mcg) per kilogram (kg) (90.9 mcg per pound) of body weight a day. Then, your doctor may increase your dose as needed.

Ambulatory Patients

Initial doses should be small (10 mg) and increased gradually, depending upon the patient's response. Ismelin (guanethidine monosulfate) has a long duration of action; therefore, dosage increases should not be made more often than every 5-7 days, unless the patient is hospitalized.

Blood pressure should be measured in the supine position, after standing for 10 minutes, and immediately after exercise if feasible. Dosage may be increased only if there has been no decrease in the standing blood pressure from previous levels. The average daily dose is 25-50 mg; only one dose a day is usually required.

Dosage Chart for Ambulatory Patients

Visits (intervals of 5-7 Days) Daily Dose
Visit 1
(Patient may be started on 10-mg tablets)
10 mg
Visit 2 20 mg
Visit 3
(Patient may be changed to 25-mg tablets whenever convenient)
30 mg
(three 10-mg tablets)
or 37.5 mg
(one and one-half 25-mg tablets)
Visit 4 50 mg
Visit 5 and subsequent Dosage may be increased by 12.5 mg or 25 mg if necessary.

The dosage should be reduced in any of the following situations:

  1. normal supine pressure;
  2. excessive orthostatic fall in pressure;
  3. severe diarrhea.

Hospitalized Patients

Initial oral dose is 25-50 mg, increased by 25 mg or 50 mg daily or every other day, as indicated. This higher dosage is possible because hospitalized patients can be watched carefully. Unless absolutely impossible, the standing blood pressure should be measured regularly. Patients should not be discharged from the hospital until the effect of the drug on the standing blood pressure is known. Patients should be told about the possibility of orthostatic hypotension and warned not to get out of bed without help during the period of dosage adjustment.

Combination Therapy

Ismelin (guanethidine monosulfate) may be added gradually to thiazides and/or hydralazine. Thiazide diuretics enhance the effectiveness of Ismelin (guanethidine monosulfate) and may reduce the incidence of edema. When thiazide diuretics are added to the regimen in patients taking Ismelin (guanethidine monosulfate) , it is usually necessary to reduce the dosage of Ismelin (guanethidine monosulfate) . After control is established, the dosage of all drugs should be reduced to the lowest effective level.

Note: When Ismelin (guanethidine monosulfate) is replacing MAO inhibitors, at least 1 week should elapse before commencing treatment with Ismelin (see CONTRAINDICATIONS). If ganglionic blockers have not been discontinued before Ismelin (guanethidine monosulfate) is started, they should be gradually withdrawn to prevent a spiking blood pressure response during the transfer period.


Tablets 10 mg - round, pale yellow, scored (imprinted CIBA 49)

Bottles of 100 NDC 0083-0049-30

Tablets 25 mg - round, white, scored (imprinted CIBA 103)

Bottles of 100 NDC 0083-0103-30

Do not store above 86° F (30° C).
Dispense in tight container (USP).

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 12/8/2004

How Supplied

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