Why is this drug prescribed?

Minoxidil (mi-NOX-i-dill) belongs to the general class of medicines called antihypertensives. It is used to treat high blood pressure (hypertension).

High blood pressure adds to the workload of the heart and arteries. If it continues for a long time, the heart and arteries may 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.

Minoxidil works by relaxing blood vessels so that blood passes through them more easily. This helps to lower blood pressure.

Minoxidil has other effects that could be bothersome for some patients. These include increased hair growth, weight gain, fast heartbeat, and chest pain. Before you take this medicine, be sure that you have discussed the use of it with your doctor.

Minoxidil is being applied to the scalp in liquid form by some balding men to stimulate hair growth. However, improper use of liquids made from minoxidil tablets can result in minoxidil being absorbed into the body, where it may cause unwanted effects on the heart and blood vessels.

Most important fact about this drug

Do not stop taking minoxidil suddenly. Stopping suddenly could cause your blood pressure to become dangerously high and could make you feel anxious or uncomfortable.

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

Avoid alcohol or use it cautiously while taking minoxidil. Alcohol may dangerously increase dizziness caused by minoxidil.

How should you take this medication?

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

Take each dose with a full glass of water.

If you are taking minoxidil with other medicines to treat high blood pressure, it is important to take each medicine at the correct, designated time as prescribed by your doctor.

Ask your doctor to teach you how to monitor your heart rate and at what heart rate you should notify them of a change.

You may not experience symptoms of hypertension while taking minoxidil, however, it is important to continue taking the medicine for as long as your doctor prescribes.

--If you miss a dose...

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

--Storage instructions...

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

What side effects may occur?

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

• An allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives);
• Numbness, tingling, pain, or weakness of your arms, legs, or face;
• Increased difficulty in breathing;
• Irregular or very fast heartbeats;
• New or worsening chest pain;
• Persistent or severe dizziness or lightheadedness; or
• Fainting.

Continue to take minoxidil and talk to your doctor when it is convenient if you experience

• A headache;
• Mild dizziness or lightheadedness;
• Water retention or weight gain--swelling of your face, stomach area, hands, feet, or ankles (call your doctor if you suddenly gain 5 or more pounds);
• Nausea, vomiting, diarrhea, or a decreased appetite;
• A rash;
• Fatigue;
• Increased hair growth; or
• Breast tenderness.

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.

Special warnings about this medication

It is important that your doctor check your progress at regular visits to make sure that this medicine is working properly.

Ask your doctor about checking your pulse rate before and after taking minoxidil. Then, while you are taking this medicine, check your pulse regularly while you are resting. If it increases by 20 beats or more a minute, check with your doctor right away.

While you are taking minoxidil, weigh yourself every day. A weight gain of 2 to 3 pounds (about 1 kg) in an adult is normal and should be lost with continued treatment. However, if you suddenly gain 5 pounds (2 kg) or more (for a child, 2 pounds [1 kg] or more) or if you notice swelling of your feet or lower legs, check with your doctor right away.

Do not take other medicines unless they have been discussed with your doctor . This especially includes over-the-counter (nonprescription) medicines for appetite control, asthma, colds, cough, hay fever, or sinus problems, since they may tend to increase your blood pressure.

Possible food and drug interactions when taking this medication

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When taking minoxidil it is especially important that your health care professional know if you are taking any of the following:

• Guanethidine (e.g., Ismelin) or
• Nitrates (medicine for angina)—Severe lowered blood pressure may occur

Special information if you are pregnant or breastfeeding

Minoxidil has not been studied in pregnant women. However, there have been reports of babies born with extra thick or dark hair on their bodies after the mothers took minoxidil during pregnancy. Discuss this possible effect with your doctor.

Studies in rats found a decreased rate of conception, and studies in rabbits at 5 times the human dose have shown a decrease in successful pregnancies. Minoxidil did not cause birth defects in rats or rabbits.

Although minoxidil passes into breast milk, it has not been reported to cause problems in nursing babies.

Recommended dosage

The dose of minoxidil will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of minoxidil. If your dose is different, do not change it unless your doctor tells you to do so:

• For oral dosage forms (tablets):
  • Adults and children over 12 years of age: 5 to 40 milligrams taken as a single dose or in divided doses.
  • Children up to 12 years of age: 200 micrograms to 1 milligram per kilogram of body weight a day to be taken as a single dose or in divided doses.

Overdosage

Seek emergency medical attention.

Symptoms of a minoxidil overdose include very low blood pressure (fainting, dizziness, confusion); an irregular heartbeat; headache; and flushing (redness, warmth).