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What is the most important information I should know about 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.

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 is 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 should I discuss with my healthcare provider before taking 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 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.