Understanding the Old Drug for Hair Growth: Minoxidil

October 13, 2025 •

5 min read

In the 1970s, a drug developed to treat high blood pressure was found to have an unexpected side effect: it caused increased hair growth. This serendipitous discovery led to minoxidil becoming the original and long-standing medication used for hair restoration, commonly known by its brand name, Rogaine.

Quick Summary

Minoxidil, initially an oral medication for hypertension, was repurposed for topical hair growth following the observation of hypertrichosis in patients. The article details minoxidil's journey from accidental discovery to its establishment as an over-the-counter hair loss treatment, its mechanism of action, efficacy, side effects, and modern use in low-dose oral formulations.

Key Points

Origin: Minoxidil was discovered accidentally as a hair growth agent while being developed as an oral medication for high blood pressure in the 1970s.
FDA Approval: Topical minoxidil (brand name Rogaine) was the first FDA-approved medication for male-pattern baldness in 1988, later also approved for female hair loss.
Mechanism: Minoxidil works by acting as a vasodilator, increasing blood flow and nutrients to hair follicles, and potentially stimulating cellular proliferation to prolong the hair growth phase.
Side Effects: Common side effects include scalp irritation, dryness, and unwanted facial hair growth. Systemic side effects are rare with topical use.
Modern Use: Dermatologists are increasingly prescribing low-dose oral minoxidil (off-label) for hair loss, finding it effective and more convenient for many patients.
Comparison with Finasteride: Unlike minoxidil's follicular stimulation, finasteride targets the hormonal cause of androgenetic alopecia by blocking the conversion to DHT.
Treatment Consistency: Minoxidil requires continuous, long-term use to maintain results; hair loss resumes within months of stopping treatment.
Patient Considerations: It's vital to consult a healthcare provider before starting any minoxidil treatment, especially the oral form, to assess suitability and monitor for side effects.

Minoxidil: From Blood Pressure to Hair Restoration

The journey of minoxidil, the old drug for hair growth, began not in dermatology, but in cardiology. Developed by the Upjohn company in the 1970s to treat severe hypertension, the oral form of minoxidil was a potent vasodilator. Clinicians soon noticed a peculiar and consistent side effect: many patients experienced hypertrichosis, or excessive hair growth, across their bodies. This observation, though initially an unwanted complication, sparked new research into the drug's potential for treating hair loss.

This led to the development of a topical formulation of minoxidil, designed to be applied directly to the scalp. In 1988, the Food and Drug Administration (FDA) approved a 2% topical minoxidil solution for treating male-pattern baldness, marketing it under the now-famous brand name, Rogaine. A few years later, a 2% solution was also approved for women with androgenetic alopecia, and a stronger 5% solution was subsequently approved for men.

The FDA approvals for minoxidil were groundbreaking, establishing it as the first clinically proven, over-the-counter solution for hair loss. Its introduction changed the landscape of hair restoration, offering a non-surgical option for millions affected by pattern baldness. Today, with its patent expired, generic versions of topical minoxidil are widely available and are a cornerstone of hair loss treatment regimens.

The Mechanism Behind Minoxidil's Action

While the precise and full mechanism of minoxidil's action remains a subject of ongoing research, scientists have identified several key ways it promotes hair growth.

Vasodilation: As a vasodilator, minoxidil widens blood vessels. In the scalp, this increases blood flow to the hair follicles, ensuring they receive more oxygen, nutrients, and hormones necessary for growth.
Potassium Channel Activation: Minoxidil is a potassium channel opener, which causes hyperpolarization of cell membranes. In the hair follicle, this process is thought to promote cell proliferation and may extend the anagen (growth) phase of the hair cycle.
Follicular Stimulation: By shortening the telogen (resting) phase and prolonging the anagen phase, minoxidil essentially coaxes dormant hair follicles back into an active growth state. It can increase the size of hair follicles, leading to thicker, more robust hairs.
Production of Growth Factors: Research indicates that minoxidil may also induce the expression of vascular endothelial growth factor (VEGF) around hair follicles, which further stimulates blood vessel formation and nutrient delivery to the hair papilla cells.

Common Side Effects of Minoxidil

Despite its long history and generally safe profile, minoxidil use can cause some side effects, particularly with topical application.

Scalp Irritation: The most common adverse effect is irritant contact dermatitis, which can manifest as itching, redness, or dryness of the scalp. This is often caused by propylene glycol, an inactive ingredient in some liquid formulations.
Unwanted Hair Growth: In some individuals, minoxidil's hair growth-promoting effects can extend beyond the scalp, leading to unwanted facial hair (hypertrichosis), especially in women.
Initial Shedding: A temporary increase in hair shedding, known as "minoxidil shedding," can occur in the first few weeks of treatment. This is a normal part of the process as old, weaker hairs are pushed out to make way for new, thicker ones.
Systemic Absorption Side Effects: While rare with topical use, if too much minoxidil is absorbed systemically, it can cause more serious cardiovascular side effects like dizziness, rapid heart rate, or swelling of the hands and feet.

Minoxidil vs. Finasteride: A Comparison

Minoxidil is often compared with finasteride, another established hair loss treatment. The key difference lies in their mechanism of action and which types of hair loss they treat.


Feature	Minoxidil	Finasteride
Mechanism	Stimulates hair follicles by shortening the resting phase and increasing blood flow.	Inhibits the enzyme 5-alpha reductase, which blocks the conversion of testosterone to dihydrotestosterone (DHT), the hormone responsible for pattern baldness.
Formulation	Primarily available as a topical foam or solution, but oral forms are increasingly used off-label.	Oral tablet taken daily.
Approval	FDA-approved for men and women with androgenetic alopecia (pattern baldness).	FDA-approved only for men with male-pattern baldness. Not approved for women due to hormonal effects.
Target	Promotes growth by revitalizing follicles, works on both genetic and non-genetic hair loss.	Directly targets the hormonal cause of androgenetic alopecia by reducing DHT levels.
Side Effects	Mostly local (scalp irritation, unwanted hair growth). Systemic effects are rare with topical use.	Potential for systemic side effects, including sexual dysfunction (decreased libido, erectile dysfunction) and depression, though uncommon.
Combination Use	Can be effectively used in combination with finasteride for a multi-pronged approach, especially in men.	Often combined with topical minoxidil to address both hormonal and follicular aspects of hair loss.

Modern Perspectives on an Old Drug

While topical minoxidil remains a staple, the medical community's approach to this old drug has evolved. A growing trend is the use of low-dose oral minoxidil (LDOM), often prescribed off-label by dermatologists. Studies have shown that oral minoxidil can be effective for various types of hair loss with a reduced risk of serious side effects compared to the high doses used for hypertension. The oral format is also more convenient for many patients who find the daily topical application messy or difficult to apply correctly.

The expiration of its patent has made generic minoxidil an extremely affordable treatment option, which, combined with the convenience of oral administration, has expanded its use through telehealth platforms. However, it is crucial that patients seeking this treatment consult with a qualified medical professional to ensure proper administration and monitor for any potential side effects, as off-label use requires expert supervision.

Conclusion

Minoxidil is undoubtedly the old drug for hair growth, with a storied history beginning in an unexpected field. Its discovery was a pivotal moment in the treatment of hair loss, moving beyond unproven remedies to a scientifically validated medication. While its topical form (Rogaine) has been the standard for decades, modern approaches leveraging low-dose oral formulations are making minoxidil an even more versatile and accessible option for patients. Its mechanism of stimulating hair follicles and increasing blood flow offers a distinct advantage, and when used either alone or in combination with other agents like finasteride, it remains a powerful tool in the arsenal against hair loss. For anyone experiencing hair thinning, understanding minoxidil's role and history is an important first step toward a potential solution. More information on minoxidil and hair loss treatments

Frequently Asked Questions

The old drug for hair growth is minoxidil. It was originally developed as an oral medication for high blood pressure but was later repurposed and approved as a topical treatment for androgenetic alopecia, or pattern baldness.

Minoxidil works by widening blood vessels and opening potassium channels, which increases blood flow to the hair follicles. This process revitalizes follicles, shortens the resting phase, and prolongs the hair's growth phase, leading to thicker and more robust hair.

Topical minoxidil is applied directly to the scalp and was the original form approved for hair loss. Oral minoxidil, now used off-label at a low dose, is taken as a pill. Studies show oral minoxidil may be more effective and convenient for some, but requires medical supervision due to systemic absorption.

Yes, common side effects include scalp irritation, itching, or dryness, often from propylene glycol in the topical solution. Other possible side effects include unwanted facial hair growth and a temporary initial shedding of hair. Severe side effects from systemic absorption are rare with topical use.

Yes, a lower-concentration topical minoxidil solution was approved for use in women with androgenetic alopecia in the 1990s. It has been shown to be effective in slowing hair loss and promoting regrowth in many women.

Initial results with minoxidil are typically seen after about 8 weeks of consistent use, with maximum effects usually becoming apparent around 4 months. However, it can take up to a year or more for some individuals to see the full effect.

If you stop using minoxidil, any hair that has been gained or preserved will likely be lost within a few months. Consistent, long-term use is necessary to maintain the benefits of the medication.