When applied topically, minoxidil can be used to treat hair loss associated with androgenic alopecia in both men and women. It is effective in 40% of men after 3-6 months of use. Even after hair regrowth, minoxidil must be applied regularly in order to support hair follicles and maintain hair growth. Its effectiveness on other forms of baldness, such as alopecia areata, is unknown. A prescription is not required for use of minoxidil, but this does not preclude the need for consulting with a healthcare provider before adding it to a healthcare regimen.
Minoxidil does not frequently cause lasting side effects in patients, but some patients react differently than others. Most commonly, patients experience a chronic itch or skin rash. Some patients may experience more rare side effects:
Acne or burns at the application sight have been observed. Because minoxidil is meant for hair growth, it may also cause unwanted facial hair growth. Hair roots may feel inflamed or sore. Facial swelling may also occur. In some cases, minoxidil may actually cause increased loss of hair.
If the body is absorbing minoxidil at a rate greater than desired, there are additional possible side effects. This is a rare outcome, but it has been observed. It may result in changes in vision. This can include blurred vision. Excess absorption may also lead to dizziness and fainting spells.
Minoxidil is an antihypertensive vasodilator, and when absorbed in excess it may lead to chest pain and an irregular or fast heartbeat. Some patients also experience lightheadedness and headaches. It has the effect of lowering blood pressure, which can lead to numbness in certain parts of the body, including the hands, feet, and face.
Lowered blood pressure caused by minoxidil may also lead to unexplained weight gain and swelling in the body. Typical areas that become swollen are the hands, feet, lower legs, and face.
In clinical trials, side effects were only observed in less than 4 percent of patients.
Patients may also experience unique side effects. People who experience side effects must notify their healthcare provider to determine if minoxidil is the cause of them.
Even though minoxidil is available without a prescription, it is important to follow the instructions provided with the container of the medicine. Failure to follow the instructions can lead to unwanted side effects as it becomes absorbed through the skin in large quantities. Additionally, as with any medication, even those available over the counter, it is important to check with a healthcare provider to be sure that it is applied in the correct quantity.
Before taking minoxidil, it is important that the patient dries their scalp and any existing hair completely. The appropriate amount of the medication must be applied to the area in need of treatment. For maximum effectiveness, application should be made with the provided applicator, starting from the center of the area and working outward.
Shampoo should not be applied to the treated area until four hours after minoxidil is applied. Patients must wash their hands thoroughly after applying the medication. Patients should not use a hairdryer to dry the treatment area, as this will reduce the medication's effect.
Actual dosage amounts vary from patient to patient. The dosage amount will vary depending on the strength of the medication, the number of doses taken each day, and the time between each dose.
On average, adults will need to use 1 milliliter of the topical solution on their scalp twice a day. If the patient is using the topical foam form of the medication, they are typically required to use half of a capful on their scalp twice a day. Children who wish to take minoxidil must be prescribed to do so by a doctor.
Patients who miss a dose of minoxidil should apply it as soon as they can, unless it is nearly time for the next dose. If this is the case, it is recommended that patients skip the missed dose and resume their regular dosing schedule at the next scheduled dose.
At these doses, minoxidil has been shown to reduce areas of hair loss in 62 percent of patients. In almost 3 percent of patients, the total area of hair loss was actually increased. These studies showed that minoxidil is only effective in patients who are experiencing hair loss as a result of androgenic alopecia. Androgenic alopecia is a form of baldness that is genetically determined and presents as gradual onset balding and increased levels of hair shedding. It can also present as a transition from thick and pigmented hair to thin, short, and uncolored hairs. Minoxidil may not be effective in any dosage if used to treat diffuse alopecia areata.
Patients who are unsure of the cause of their baldness should consult with their healthcare provider before using any dosage of minoxidil. A healthcare provider can typically determine the cause of baldness based on patient history and a physical examination of the patient. If necessary, a healthcare provider may also conduct laboratory tests including a DHEA-sulfate and testosterone analysis in women, a thyrotropin test to determine the presence of a thyroid disorder, and iron binding capacity, and transferrin saturation tests to test for iron deficiencies and for the presence of telogen effluvium.
As with any other medication, minoxidil may react negatively with other medications. Negative reactions may reduce the effectiveness of minoxidil or other medications that a patient is taking. This can be dangerous for patients on medication that is essential to their health. It is important for all patients to notify their healthcare provider before beginning any new medication regimen. This includes any non-prescription drugs, herbal supplements, and vitamins.
Major negative interactions may be experienced by patients who are taking guanethidine, hydrochlorothiazide, guanadrel, tizanidine, or other blood pressure medication. Using minoxidil while taking blood pressure medication can cause low blood pressure and reduced heart rate. This can lead to dizziness, headaches, and fainting. Minoxidil, like blood pressure medication, is an antihypertensive vasodilator. This means patients taking both medications may need their dosage of minoxidil reduced or their blood pressure checked on a more regular basis.
Other medications that lower a patient's blood pressure as a side effect, including clozapine, codeine, morphine, and acetaminophen, may also interact with minoxidil.
Medications that interact with alcohol, such as those used to treat bacterial infection (metronidazole) and alcoholism (disulfiram) may also have a negative reaction with minoxidil. Many topical preparations of minoxidil may contain alcohol and propylene glycol, which may react with drugs that react with alcohol.
Patients should always consult with their healthcare provider before adding medication to their regimen.
Before adding any medication to their regimen, a patient should consult with their healthcare provider or pharmacist. Minoxidil could contain active or inactive ingredients that a patient may be allergic to. Patients who have diseases of the scalp including eczema and infection, heart problems, or kidney or liver diseases should exercise extreme caution before taking minoxidil and notify their doctor.
Minoxidil falls under pregnancy category C as assigned by the FDA. While animal studies have failed to show any evidence of teratogenicity (the property of a drug to negatively impact the development of an embryo or fetus), reduced conception rates and increased risk of fetal absorption has been observed in animal studies where rabbits were given five times the normal amount of a typical human dose.
While not observed in topical application, congenital abnormalities have been observed in human pregnancy in which the mother was taking oral minoxidil. There were only two cases of congenital abnormality observed, and in both of these cases pre-existing hypertension and the use of other medication make it difficult to associate minoxidil as the sole cause of fetal abnormalities. Hypertrichosis, which presents as excess hair growth, was observed in both of these cases.
Topical minoxidil is not absorbed in the blood stream at the same rate as oral minoxidil, but it can be when used excessively. There is limited data about humans breastfeeding while taking oral minoxidil, stemming from a single study. This study showed that minoxidil can be present in breast milk. The potential for negative effects in infants that are nursing leads to a warning that mothers who are breastfeeding should not take oral or topical minoxidil.
Topical minoxidil should not be used by those who have sudden or patchy hair loss, or by women whose hair loss is associated with pregnancy. It should also not be used by people who do not know the cause of their hair loss, or people who are already using other forms of medication on their scalps.
Minoxidil should be kept in the container that it was purchased in. It must be stored with the cap closed tightly, and put in a place that children cannot access. Minoxidil should not be stored in the bathroom. It must be stored in a place that is constantly at room temperature. It should never be stored where there is excess heat or moisture.
All medication should be kept in a place that is not accessible to children, especially medication that is not in a child proof container. Children may be poisoned if they gain access to any medication, including minoxidil.
If a patient discontinues use of minoxidil, they should dispose of it so that children, animals, and other people cannot use it. Flushing the medication down the toilet is not an appropriate method of disposal. Patients should consult with their pharmacist to find out about local medication disposal programs. If there is no local medication disposal program, the FDA recommends the following method for disposal of all medications:
If the drug has a container with any prescribing information, start by scratching out any identifying information. Then, any remaining medication should be mixed with an appropriate amount of an unpalatable substance. This substance could be dirt, cat litter, or even used coffee grounds. The mixture should then be placed in a disposable container, such as a sealable plastic bag. This container can then be thrown in with the regular garbage.
Patients who take minoxidil can see increased hair growth without many negative benefits as long as they consult with their healthcare provider before adding it to their medication regimen. For many patients, side effects are minimal to non existent. This, however, does not preclude the necessity for seeking medical advice before using minoxidil. The reason that minoxidil works for hair growth is not completely understood. It is believed that, as a potassium channel opener that causes hyperpolarization of cell membranes, minoxidil is able to allow more oxygen, blood, and nutrients to flow to the follicles. This is believed to cause follicles that are in the telogen phase to fall out and be replaced by thicker hairs that are in the anagen phase.
Minoxidil is more effective when used by young men with smaller areas of hair loss. It is also more effective in patients who have been experiencing hair loss for less than five years. It is not indicated for use to resolve hair loss in parts of the body other than the top of the head, known as the vortex.
Minoxidil is an over the counter medication but can still have adverse effects, especially on patients who are taking certain other medications. Patients who are maintaining proper blood pressure through the use of medication are especially prone to adverse side effects. Women who are nursing, pregnant, or may become pregnant should not use minoxidil as it is possible that it can be absorbed internally after topical application and effect the fetus and breastmilk. As with any medication, including over the counter medications, it is important to be aware of drug interactions.