Oral minoxidil (low dose) and Blood pressure medicines (and other medicines that lower blood pressure)
ASK PRESCRIBER
ASK PRESCRIBER: oral minoxidil lowers blood pressure, and the Loniten SmPC states that 'the effect of minoxidil may be additive to concurrent antihypertensive agents and other agents with blood pressure lowering effects'. If you take any medicine that lowers blood pressure, your prescriber needs to know before you start.
Mechanism
Minoxidil was first licensed as a blood pressure medicine. It relaxes the small arteries, which lowers blood pressure. Any other medicine that lowers blood pressure, by whatever route, adds to that effect. The BNF lists more than 150 interactions for minoxidil, and most read the same way: both medicines 'can increase the risk of hypotension' (low blood pressure).
That list goes well beyond tablets prescribed for high blood pressure (ACE inhibitors such as ramipril, beta-blockers such as atenolol or bisoprolol, calcium channel blockers such as amlodipine, and diuretics such as bendroflumethiazide). It also includes alpha-blockers taken for prostate symptoms (tamsulosin, alfuzosin, doxazosin), nitrates for angina (glyceryl trinitrate, isosorbide mononitrate), erectile dysfunction medicines (see oral minoxidil and sildenafil), some antidepressants such as amitriptyline, and alcohol.
The Loniten SmPC singles out one combination: sympathetic-blocking agents such as guanethidine 'may produce excessive blood pressure reduction and/or orthostatic hypotension' (a drop in blood pressure on standing). At its licensed antihypertensive doses, minoxidil is deliberately given alongside a diuretic and a beta-blocker, so combining it with other blood pressure medicines is not forbidden. It needs planning. Low-dose minoxidil for hair loss is off-label, and its doses are much lower than the licensed starting dose for severe hypertension, but the direction of the effect is the same.
Practical advice
Before starting: list every medicine you take in your online assessment, including ones from a hospital clinic, a GP, a pharmacy or abroad. A GMC-registered doctor reviews this before deciding whether oral minoxidil is suitable, and may choose a lower starting dose or decide it is not right for you. Our how it works page explains the assessment.
While taking both: watch for the symptoms of low blood pressure that the NHS lists: lightheadedness or dizziness, feeling sick, blurred vision, feeling weak, confusion and fainting. Get up slowly from sitting or lying, take care getting out of bed, drink enough fluids, and do not drink too much alcohol. A home blood pressure monitor can give useful readings to share with your prescriber.
If anything changes: tell your prescriber if another clinician starts, stops or changes a blood pressure medicine, and tell that clinician you take oral minoxidil. Do not stop a prescribed blood pressure medicine yourself to make room for minoxidil.
Get help: see a GP if you keep getting dizzy spells or fainting. Call 999 for chest pain, breathlessness at rest or collapse. Related reading: oral minoxidil and cardiovascular effects, oral minoxidil and ankle swelling and the minoxidil oral tablets page.