Drug Breakdown: Minoxidil

Day 1: A vasodilator derived from diallylmelamine in 1960s was found to have a BP lowering effect & #minoxidil was licensed 1970s. Long-term use revealed side-effect of hypertrichosis & trials for alopecia & male pattern baldness ensued. Licensed for male hair loss in 1988 as a topical formulation, then 1992 for female hair loss

Day 2: #minoxidil topical 5% solution is licensed for (wo) men aged 18-65 years. It is applied x 1-2/day when the reason for hair loss is known (OTC/private prescription); 5% foam can be prescribed on NHS. Full effect can take 6 months+. Low dose oral #minoxidil (0.625-2.5mg) is used by specialists off-label e.g for alopecia, including for children over 12 years (topical use not recommended in children). Oral 1mg approx equivalent to 5% solution

Day 3: Oral version is a prodrug & genetics determine breakdown response (weak in 50% as less active drug released (if low SULT1A1)). Avoid if severe hepatic impairment. Topical absorption is minimal from intact skin (1-2% of applied dose). All routes metabolised in liver & renal excretion.T½ 4-5 hrs