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Guanethidine sulfate and Hydrochlorothiazide oral

Important Note

The following information is intended to supplement, not substitute for, the expertise and judgment of your physician, pharmacist or other healthcare professional. It should not be construed to indicate that use of the drug is safe, appropriate, or effective for you. Consult your healthcare professional before using this drug.


(gwan-ETH-eh-deen WITH HI-dro-klor-oh-THIGH-uh-zide)


WARNING: This medication can frequently cause dizziness and weakness which may lead to fainting, especially when first starting this medication. Symptoms occur more often upon awakening and may increase during hot weather, exercise, or when drinking alcohol. To avoid fainting do not stand quickly and avoid standing or exercising for long periods of time. This combination product must not be the first treatment used to control high blood pressure.


Guanethidine helps to widen arteries and veins so blood flows better. Hydrochlorothiazide (HCTZ) is a diuretic "water pill", that rids the body of excess fluid. This combination medication is used to treat hypertension (high blood pressure).

How To Use

Take this medication by mouth with food or milk as directed. Try to take it at the same time each day so you get into the habit of taking it. Do not stop taking this medication without first consulting your doctor. It is important to continue taking this medication even if you feel well. Most people with high blood pressure do not feel sick.

Side Effects

Dizziness, drowsiness, headache, lightheadedness, diarrhea, constipation, loss of appetite, nausea, fatigue or weakness may occur the first several days as your body adjusts to the medication. Dry mouth, nasal congestion, weight gain, sun sensitivity, muscle tremors, nightmares, decreased sexual desire or ability and trouble urinating may also occur. If any of these effects continue or become bothersome, inform your doctor. This medication increases urination. Expect this effect. To avoid dizziness and lightheadedness when rising from a seated or lying position, get up slowly. Also limit your intake of alcoholic beverages and avoid overheating which will aggravate these effects. Notify your doctor if you develop: chest pain, a rapid pulse, difficulty breathing, skin rash, depression, tingling of the hands or feet, unusual weakness, joint pain, muscle cramps, unusual bleeding or bruising, jaundice, severe stomach upset or vomiting. If you notice other effects not listed above, contact your doctor or pharmacist.


Tell your doctor if you have: kidney problems, heart disease, ulcers, depression, asthma, diabetes, gout, blood disorders, allergies (especially to sulfa medications). This medication may increase your sensitivity to the sun. Avoid prolonged sun exposure and wear protective clothing and a sun screen when outdoors. This medication should be used only if clearly needed during pregnancy. Discuss the risks and benefits with your doctor. Since small amounts of this medication are found in breast milk, consult your doctor before breast-feeding.

Drug Interactions

This drug is not recommended for use with: dofetilide. Ask your doctor or pharmacist for more details. Tell your doctor of any over-the-counter or prescription medication you take, especially of: heart drugs, blood pressure drugs, high cholesterol drugs, diabetes medication, antidepressants. Do not take any medication for cough, colds, hay fever, allergies or weight control without first checking with your doctor or pharmacist. These medications may contain ingredients which can increase blood pressure. Diabetics must be aware that this medication may affect blood sugar levels. Discuss this with your doctor. Do not start or stop any medicine without doctor or pharmacist approval.


If overdose is suspected, contact your local poison control center or emergency room immediately. Symptoms of overdose may include fainting or severe dizziness, unusually slow pulse, nausea, and vomiting.


It is important to have your blood pressure checked regularly while taking this medication. Learn how to take your blood pressure and understand the readings. Discuss this with your doctor or pharmacist.

Missed Dose

If you miss a dose, take it as soon as remembered; do not take it if it is near the time for the next dose, instead, skip the missed dose and resume your usual dosing schedule. Do not "double-up" the dose to catch up.


Store at room temperature between 59 and 86 degrees F (15 to 30 degrees C) away from heat and light. Do not store in the bathroom.