Type of drug

POM

Presentation

(Soft) capsules, tablets (modified or prolonged release)

Dosage

Hypertension: 10 mg stat, 10 mg b.d.
Tocolytic: see Chapter 18 for regimen if used as myometial relaxant

Route of admin

Oral (preferably sublingual during hypertensive crisis)

Contraindications

Continuous use in pregnancy, breastfeeding, hypersensitivity

Side effects

Headache, flushing, dizziness, oedema, may inhibit labour
CAUTION: stop treatment if ischaemic pain occurs within 30–60 min of administration; treatment with short-acting nifedipine, i.e. during a crisis, can induce an exaggerated fall in blood pressure and reflex tachycardia, which may cause complications such as cerebrovascular accident/ischaemia or myocardial ischaemia
EXTREME CAUTION when using magnesium sulphate

Interactions

Do not take with grapefruit juice
Antihypertensives – causes severe hypotension and possible heart failure
Cimetidine – potentiates the hypotensive effect as metabolism of nifedipine is inhibited

Phenytoin – concomitant administration can reduce the effect of nifedipine – monitor plasma levels of anticonvulsants
Erythromycin – may potentiate nifedipine effects
Insulin – possible impaired glucose tolerance

Pharmacodynamic properties

Selective calcium channel blocker with mostly vascular effects. It is a specific and potent calcium antagonist that relaxes smooth arterial muscle, causing arteries to widen, thereby reducing the resistance in coronary and peripheral circulation. This reduces blood pressure and decreases the heart’s overall workload

Fetal risk

Contraindicated in pregnancy before week 20; toxicity and teratogenicity in animals; hypotensive effect can reduce placental flow and cause decrease in fetal oxygenation; may inhibit labour

Breastfeeding

No known adverse side effects (NICE, 2010), but manufacturer advises avoidance

BP

Methyldopa

Proprietary

Aldomet^® (Aspen)
Methyldopa (Actavis UK Ltd)
Methyldopa (non-proprietary, see BNF for details)

Group

Centrally acting antihypertensive

Uses/indications

Hypertension in pregnancy, hypertensive crisis where immediate effect is not necessary, can be used by asthmatics

Type of drug

POM

Presentation

Tablets

Dosage

Oral: 250 mg b.d. (t.d.s.) max 3 g/day, gradually increased at intervals of 2 days or more

Route of admin

Oral

Contraindications

History of depression, liver disease, phaeochromocytoma, concurrent treatment with MAOIs, porphyria, history of hepatic or renal dysfunction

Side effects

Reduced if under 1 g/day, dry mouth, sedation, depression, fluid retention, haemolytic anaemia, SLE-like syndrome, postural hypotension, gastrointestinal disturbances, dizziness, headache, numbness, hyperprolactinaemia, nightmares, mild psychosis, blood disorders, nasal congestion, nerve and joint pain, hepatic disorders; may interfere with laboratory results – 20% have a positive DCT – advise laboratory of treatment if requiring crossmatch