BMA Concise Guide to Medicine & Drugs

Minoxidil

Brand names Boots Hair Loss Treatment, Loniten, Regaine

Used in the following combined preparations None

QUICK REFERENCE

Drug group Antihypertensive drug and treatment for hair loss

Overdose danger rating Medium

Dependence rating Low

Prescription needed Yes (except for scalp lotions)

Available as generic No

GENERAL INFORMATION

Minoxidil is a vasodilator drug that works by relaxing the muscles of artery walls and dilating blood vessels. It is effective in controlling dangerously high blood pressure that is rising very rapidly. Because minoxidil is stronger acting than many other antihypertensive drugs, it is particularly useful for people whose blood pressure is not controlled by other treatment.

Because minoxidil causes significant fluid retention and increased heart rate, it should be prescribed with a diuretic and a beta blocker to increase effectiveness and to counteract its side effects. Unlike many other drugs in the antihypertensive group, minoxidil rarely causes dizziness and fainting. Its major drawback is that, if it is taken for more than two months, it increases hair growth, especially on the face. Although this effect can be controlled by shaving or depilatories, some people find the abnormal growth distressing. This effect is put to use, however, to treat baldness in men and women, and for this purpose minoxidil is applied locally as a solution.

INFORMATION FOR USERS

Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets, topical solution.

Frequency and timing of doses Once or twice daily.

Adult dosage range 5mg daily initially, increasing gradually to a maximum of 50mg daily.

Onset of effect Blood pressure Within 1 hour (tablets). Hair growth Up to 1 year (solution).

Duration of action Up to 24 hours. Some effect may last for 2–5 days after stopping the drug.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Take as soon as you remember (tablets). If your next dose is due within 5 hours, take a single dose now and skip the next. If used topically for baldness, any regained hair will be lost when the drug is stopped.

Stopping the drug Do not stop the drug without consulting your doctor; stopping the drug may lead to worsening of the underlying condition.

Exceeding the dose An occasional unintentional extra dose is unlikely to cause problems. Large overdoses may cause nausea, vomiting, palpitations, or dizziness. Notify your doctor.

POSSIBLE ADVERSE EFFECTS

Fluid retention is a common adverse effect of minoxidil, which may lead to ankle swelling and an increase in weight; diuretics are often prescribed to control this effect. Increased growth of hair on the head and body is another common effect. More rarely, there may be nausea, breast tenderness, dizziness, lightheadedness, or a rash; consult your doctor if any of these occur. If you experience palpitations, stop taking the drug and consult your doctor immediately. In some cases, allergic and irritant dermatitis may occur with minoxidil lotion.

INTERACTIONS

Antidepressant drugs The hypotensive effects of minoxidil may be enhanced by antidepressant drugs.

Other antihypertensives These drugs may increase the effects of minoxidil.

Oestrogens and progestogens (including those in some contraceptive pills) may reduce the effects of minoxidil.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You have a long-term kidney problem.

· You have heart problems.

· You are taking other medicines.

Pregnancy Safety in pregnancy not established. Discuss with your doctor.

Breast-feeding The drug passes into the breast milk, but at normal doses adverse effects on the baby are unlikely. Discuss with your doctor.

Infants and children Reduced dose necessary.

Over 60 Reduced dose may be necessary.

Driving and hazardous work Avoid such activities until you have learned how minoxidil affects you because the drug can cause dizziness and lightheadedness.

Alcohol Avoid. Alcohol may further reduce blood pressure.

Surgery and general anaesthetics Minoxidil treatment may need to be stopped before you have a general anaesthetic. Discuss this with your doctor or dentist before any surgery.

PROLONGED USE

Prolonged use of this drug may lead to swelling of the ankles and increased hair growth.