Minoxidil

Source: Minoxidil 10 mg Tablets SPC §4.2 (oral minoxidil for hypertension). Dose increases should be made in increments of 5 mg to 10 mg per day at intervals of three or more days. Rapid reduction of blood pressure: under hospital monitoring conditions this can be achieved using continuous blood pressure monitoring and incremental doses of 5 mg every six hours. Elderly: no extensive clinical studies over age 65; elderly patients may be sensitive to the blood-pressure-lowering effect and orthostatic hypotension may occur — an initial starting dose of 2.5 mg per day is suggested in patients over 65. Mandatory co-therapy per SPC §4.2: minoxidil causes sodium retention, so in all patients not on dialysis it must be given with a diuretic in sufficient dosage to maintain salt and water balance (examples of daily starting dosages quoted: hydrochlorothiazide 100 mg or another thiazide at equi-effective dosage, chlortalidone 100 mg, or furosemide 80 mg; switch to furosemide if water retention causes weight gain over 3 pounds on a thiazide/chlortalidone). Patients also require a sympathetic nervous system suppressant to limit minoxidil-induced rise in heart rate — the preferred agent is a beta-blocker equivalent to an adult propranolol dosage of 80-160 mg/day (higher doses may be needed if heart rate rises by more than 20 bpm in pre-treated patients or more than 10 bpm on simultaneous introduction); where beta-blockers are contraindicated, alternatives such as methyldopa may be used and should be started 24 hours before minoxidil. Where possible, antihypertensive therapy other than a beta-adrenergic blocking agent and a diuretic should be discontinued before starting minoxidil, tapering gradually over the first week for drugs that should not be stopped abruptly. NOTE: the US openFDA record retrieved for 'minoxidil' was a topical over-the-counter hair-regrowth product (different indication and route) and was NOT used for this oral antihypertensive dose.

SPC §4.2, patients younger than 12 years: use is restricted to children with severe hypertension associated with target organ damage where other treatment has failed. Data are very limited (a few case reports and small studies), especially in infants, and the recommendations are only a rough guide. Starting dose 0.2 mg/kg as a single or divided dose; careful titration in steps of 0.1 to 0.2 mg/kg/day at intervals of at least 3 days is essential; effective dose range 0.25 to 1.0 mg/kg/day; maximum dose 50 mg/day. Treatment of children with minoxidil should only be initiated under the close supervision of a specialist in hospital. Diuretic dosage in children should be proportionally less in relation to weight. Verify against a children's formulary before prescribing.