NIFEDIPINE

Calcium channel blocker antihypertensive. Also used in low doses as anti-oxytocic uterine relaxant

Dosage Forms

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Tablet

20 mg (usually labelled 'R' for prolonged release)
10 mg

Immediate release capsules

10 mg for sublingual use

Uses

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  • Moderate and severe hypertension
  • Uncomplicated threatened premature labour between 24–33 weeks of pregnancy (labour can be delayed up to 72 hours)

Dose and Duration

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Moderate or severe hypertension (in combination with other antihypertensive)

20–40 mg every 12 hours for as long as necessary

Threatened premature labour

Initially, 10 mg (1 capsule) placed under the tongue every 15 minutes if necessary, up to a maximum of 40 mg in the first hour. Then 60–160 mg daily in 3–4 divided doses, adjusted to uterine activity

Contraindications

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  • Severe heart disease
  • Unstable angina
  • Shock
  • Recent heart attack

Side Effects

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  • Headache, dizziness
  • Swelling of legs, ankles, and feet
  • Increased frequency of urination
  • Low blood pressure, flushing
  • Fast heartbeat
  • Pain in the eyes
  • Visual disturbances
  • Nausea

Interactions

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  • Beta blockers e.g. atenolol, propranolol (possible severe hypotension and heart failure)
  • Digoxin (increased plasma concentration of digoxin)
  • Magnesium sulphate (risk of hypotension )
  • Salbutamol (risk of hypotension )
  • Other calcium channel blockers e.g. amlodipine (risk of hypotension )
  • Rifampicin (reduced effect of nifedipine)

Patient Instructions

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  • Do not crush prolonged release tablets; swallow whole
  • If sharp pain/tightness occurs in the chest, discontinue use

Pregnancy

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  • Do not use for hypertension

Breast-feeding

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  • Can be used

⚠️ Caution

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  • Never use the sublingual formulation (10 mg capsule) for hypertension as it will cause excessive fall in blood pressure and reduced blood flow to the brain and heart
  • Methyldopa is the medicine of choice for treating hypertension in pregnancy