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Ismelin

Generic Name: guanethidine (gwha NETH ih deen)
Brand Name: Ismelin

What is Ismelin (guanethidine)?

Guanethidine lowers blood pressure by decreasing the levels of certain chemicals in the blood. This allows your blood vessels (veins and arteries) to relax (widen).

Guanethidine is used to treat hypertension (high blood pressure). Guanethidine is also used to treat high blood pressure in the kidneys.

Guanethidine may also be used for purposes other than those listed in this medication guide.

What is the most important information I should know about Ismelin (guanethidine)?

Use caution when driving, operating machinery, or performing other hazardous activities. Guanethidine may cause dizziness or drowsiness. If you experience dizziness or drowsiness, avoid these activities.

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Use caution when rising from a sitting or lying position, especially first thing in the morning. Dizziness may occur while taking guanethidine and may result in a fall.

Do not stop taking guanethidine suddenly without first talking to your doctor. This could cause severely high blood pressure, nervousness, and anxiety.

Before having surgery, tell your doctor or dentist that you are taking this medication.

What should I discuss with my healthcare provider before taking Ismelin (guanethidine)?

You cannot take guanethidine if you

  • have pheochromocytoma;

  • have congestive heart failure; or

  • are taking a monoamine oxidase inhibitor such as isocarboxazid (Marplan), phenelzine (Nardil), or tranylcypromine (Parnate).

Before taking this medication, tell your doctor if you

  • have peptic ulcer disease (stomach ulcers) or another stomach disease;

  • have gallstones,

  • have kidney disease;

  • have any type of heart disease;

  • have asthma;

  • have ulcerative colitis;

  • are suffering from depression (especially if you have suicidal thoughts); or

  • are receiving electroconvulsive shock therapy.

You may require a dosage adjustment or special monitoring during treatment if you have any of the conditions listed above.

Guanethidine is in the FDA pregnancy category C. This means that it is not known whether guanethidine will be harmful to an unborn baby. Do not take guanethidine without first talking to your doctor if you are pregnant or could become pregnant during treatment.

Guanethidine passes into breast milk and may be harmful to a nursing infant. Do not take guanethidine without first talking to your doctor if you are breast-feeding a baby.

How should I take Ismelin (guanethidine)?

Take guanethidine exactly as directed. If you do not understand these directions, ask your pharmacist, nurse, or doctor to explain them to you.

Take each dose with a full glass of water.

Take guanethidine with food or milk if it causes stomach upset.

It is important to take guanethidine regularly to get the most benefit.

Do not stop taking guanethidine suddenly without first talking to your doctor. This could cause severely high blood pressure, nervousness, and anxiety.

Your doctor may want you to have blood pressure monitoring or other medical evaluations during treatment with guanethidine to monitor progress and side effects.

Store this medication at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. However, if it is almost time for the next dose, skip the dose you missed and take only the next regularly scheduled dose. Do not take a double dose of this medication.

What happens if I overdose?

Seek emergency medical attention if an overdose is suspected.

Symptoms of a guanethidine overdose include low blood pressure (fainting, dizziness, weakness); a slow pulse; low body temperature; diarrhea; and slow breathing.

What should I avoid while taking Ismelin (guanethidine)?

Use caution when driving, operating machinery, or performing other hazardous activities. Guanethidine may cause dizziness or drowsiness. If you experience dizziness or drowsiness, avoid these activities.

Use caution when rising from a sitting or lying position, especially first thing in the morning. Dizziness may occur while taking guanethidine and may result in a fall.

Avoid alcohol while taking guanethidine. It may increase drowsiness an dizziness caused by guanethidine. Use caution even with small amounts of alcohol.

Guanethidine may increase the effects of other drugs that cause drowsiness, including antidepressants, alcohol, antihistamines, pain relievers, anxiety medicines, seizure medicines, and muscle relaxants. Dangerous sedation, dizziness, or drowsiness may occur if guanethidine is taken with any of these medications. Tell your doctor about all medicines that you are taking, and do not take any medicine without first talking to your doctor.

Avoid becoming overheated in hot weather or during exercise. Also avoid standing for long periods of time and use caution if you have a fever. These situations increase the effects of guanethidine in the body and may cause dizziness.

Before having surgery, tell your doctor or dentist that you are taking this medication.

Ismelin (guanethidine) side effects

If you experience any of the following serious side effects, stop taking guanethidine and seek emergency medical attention or contact your doctor immediately:

  • an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives);

  • irregular heartbeats;

  • heart failure (shortness of breath, swelling of ankles or legs, sudden weight gain of 5 pounds or more); or

  • chest pain.

Other, less serious side effects are more likely to occur. Continue to take guanethidine and talk to your doctor if you experience

  • unusual fatigue or drowsiness;

  • dizziness (avoid standing up to quickly and use caution when performing hazardous activities);

  • anxiety, depression, or nightmares;

  • diarrhea, nausea, or vomiting (take guanethidine with food or milk if it upsets your stomach);

  • stuffy nose or a dry mouth (sucking on ice chips or sugarless hard candy may relieve a dry mouth);

  • blurred vision;

  • weight gain; or

  • impotence or difficulty ejaculating.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

See also: Side effects (in more detail)

What other drugs will affect Ismelin (guanethidine)?

Do not take guanethidine without first talking to your doctor if you have taken a monoamine oxidase inhibitor (MAOI) such as isocarboxazid (Marplan), phenelzine (Nardil), or tranylcypromine (Parnate) in the last 14 days.

Before taking this medication, tell your doctor if you are taking any of the following medicines:

  • haloperidol (Haldol);

  • methylphenidate (Ritalin);

  • minoxidil (Loniten);

  • thiothixene (Navane);

  • respiratory medicines such as albuterol (Ventolin, Proventil, Volmax, others), pirbuterol (Maxair), salmeterol (Serevent), and others;

  • phenothiazines such as chlorpromazine (Thorazine), prochlorperazine (Compazine), perphenazine (Trilafon), fluphenazine (Prolixin), thioridazine (Mellaril), and others; or

  • tricyclic antidepressants such as amitriptyline (Elavil, Endep), imipramine (Tofranil), doxepin (Sinequan), nortriptyline (Pamelor), and others.

You may require special monitoring or a dose adjustment if you are taking any of the medicines listed above.

Drugs other than those listed here may also interact with guanethidine or affect your condition. Talk to your doctor and pharmacist before taking any prescription or over-the-counter medicines, including vitamins, minerals, and herbal products.

Where can I get more information?

  • Your pharmacist has additional information about guanethidine written for health professionals that you may read.

What does my medication look like?

Guanethidine is available with a prescription under the brand name Ismelin. Other brand or generic formulations may also be available. Ask your pharmacist any questions you have about this medication, especially if it is new to you.

  • Ismelin 10 mg--round, pale-yellow, scored tablets

  • Ismelin 25 mg--round, white, scored tablets

  • Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.
  • Disclaimer: Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2012 Cerner Multum, Inc. Version: 5.02. Revision Date: 2/13/04 3:58:27 PM.

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