- Drugs List
- Therapeutic Indications
- Precautions and Warnings
- Pregnancy and Lactation
- Side Effects
Oral formulations of minoxidil
Hypertension - severe (when given with a beta-blocker and diuretic)
If the desired decrease of diastolic blood pressure exceeds 30mmHg, then dosage should be divided in two daily doses to keep daily blood pressure fluctuations as low as possible.
Initial dose: 5mg daily.
Maintenance dose: Increase dose, if required, to 20mg daily, and then to 40mg daily (as a single dose or in two divided doses).
Dose should be increased in increments of 5mg to 10mg daily, and at intervals of not less than three days. If a 50mg dose has been reached, the dose may be increased by 25mg daily.
Maximum dose: 100mg daily.
Initial dose: 2.5mg daily.
Maintenance dose: (See Dosage; Adult).
Children age 12 to 18 years
(See Dosage; Adult)
Children aged 11 years or younger
Initial dose: 0.2mg/kg daily as a single or divided dose.
Maintenance dose: Increase dose, if required, in increments of 0.1mg/kg to 0.2mg/kg daily, at intervals of not less than three days.
Usual dose range: 0.25mg/kg to 1mg/kg daily.
Maximum dose: 50mg daily. Some sources suggest a maximum daily dose of 1mg/kg.
Additional Dosage Information
Minoxidil causes sodium and water retention and a rise in heart rate. Therefore treatment must be given in conjunction with a diuretic (except patients on dialysis) and a beta blocker, or appropriate alternative, to control reflex tachycardia.
Examples of daily dosages of diuretics commonly used on initiation of treatment are:
Hydrochlorothiazide 100mg daily
Chlortalidone 100mg daily
Furosemide 80mg daily.
If excessive water retention results in weight gain of more than 3 pounds when a thiazide or chlortalidone is used, change diuretic to furosemide, the dose of which may be increased according to the patient's requirements.
Diuretic dosage in children should be a proportion of the adult dose based on the weight of the child.
The preferred sympathetic nervous system suppressant is a beta blocker. In adults doses equivalent to 80mg to 160mg per day propranolol may be used. Higher doses may be required when pre-treated patients have an increase in heart rate exceeding 20 beats per minute or when simultaneous introduction causes an increase exceeding 10 beats per minute.
When beta blockers are contraindicated alternatives such as methyldopa can be used and should be started 24 hours prior to minoxidil.
Under hospital monitoring conditions, rapid reduction of blood pressure can be achieved using continuous blood pressure monitoring and incremental doses of 5mg every 6 hours.
Precautions and Warnings
Patients over 65 years
Congestive cardiac failure
Glucose-galactose malabsorption syndrome
Recent myocardial infarction (until stabilised)
Haemodialysis patients: administer drug after or 2 hours before dialysis
If renal function impaired, reduce dose to lowest to maintain control
Administer with a diuretic and beta blocker, or appropriate substitute
Advise ability to drive/operate machinery may be affected by side effects
Reduce initial dose in the elderly
Consider changing diuretics if weight gain >3lb
Monitor fluid and electrolyte status
Monitor for signs of pericardial effusion in all patients
Monitor patient's weight
Monitor urine output
Advise patient of risk of hypertrichosis
May cause changes to ECG
Consider discontinuing therapy if pericardial effusion persists
Dietary salt restriction may be necessary
Advise diuretic compliance: reduced drug effect if 2 to 3lb weight gain
Pregnancy and Lactation
Minoxidil is contraindicated in pregnancy.
There is limited data available from the use of minoxidil in pregnant women.
Minoxidil is not acceptable to use in pregnancy as it has teratogenic risks, can cause foetal hypertrichosis and individual cases report newborns with different birth defects. However, inadvertent exposure does not justify either interruption of pregnancy or invasive diagnostic procedures (Schaefer et al, 2007). Briggs (2015) states data on the use of minoxidil in human pregnancy is too limited to determine the risk or teratogenicity. It is not teratogenic in rats and rabbits, however some foetal toxicity was observed in rabbits. Minoxidil should be avoided in pregnancy due to possible risk of large orthostatic decreases in blood pressure that could severely jeopardize placental perfusion and neonatal hirsutism.
The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
Use minoxidil with caution in breastfeeding.
Minoxidil is excreted in breast milk, however the amount is unlikely to be harmful (Hale et al, 2014). Briggs (2015) considers minoxidil as compatible with breastfeeding, however long-term use in breastfeeding may not be advisable. The Drugs and Lactation Database (LactMed) states to use minoxidil in breastfeeding with caution, particularly in large doses and in newborns. A decision must be made whether to discontinue minoxidil treatment or to discontinue breastfeeding after assessing the benefits for the child being breastfed and the benefits of the treatment for the mother.
Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
Specialist advice is available from the UK Drugs in Lactation Advisory Service at https://www.midlandsmedicines.nhs.uk/content.asp?section=6&subsection=17&pageIdx=1
Aggravation of angina
Changes in hair colour
Increase in blood urea nitrogen
Increase in creatinine
Pericardial effusion with associated tamponade
It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.
The following number will direct the caller to the relevant local centre (0844) 892 0111
Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
Last Full Review Date: September 2016
Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 2nd edition (2007) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.
Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 10th edition (2015) ed. Briggs, G., Freeman, R. Wolters Kluwer Health, Philadelphia.
Medications and Mothers' Milk, Sixteenth Edition (2014) Hale, T and Rowe, H, Hale Publishing, Plano, Texas.
Summary of Product Characteristics: Loniten tablets 2.5 mg. Pfizer Ltd. Revised June 2016.
Summary of Product Characteristics: Loniten tablets 5 mg. Pfizer Ltd. Revised June 2016
Summary of Product Characteristics: Loniten tablets 10 mg. Pfizer Ltd. Revised June 2016
NICE Evidence Services Available at: www.nice.org.uk Last accessed: 13 September 2017
US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
Available at: https://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT
Last accessed: 19 September 2016.
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Medscape UK | Univadis prescription drug monographs & interactions are based on FDB Multilex Content
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