Prepared By MARIAM SALEH ALAMRO A Calcium Channel Blocker

Physical Properties : Nifedipine is a: * yellow *crystalline *water insoluble substance.

Its structure is as follow :

Formulation : The drug is available as capsules or extended release tablets. They must be swallowed as whole not chewed, divided nor crushed.

Here are some of these formulations : AdalatProcardia XL

Pharmacokinetics : * Completely absorbed after oral administration. (extended release tablets must be taken on an empty stomach 1 hour bofore or 2 hours after the meal. In contrast, capsules can be taken either with food or without) * Widely distributed. (found in hippocampal neurons of experimental rats)

* Metabolized mainly in gastrointestinal tract and to lesser extent in the liver. The metabolites are inactive and water soluble. * Excreted mainly in the urine. * Highly protein binding. * Half life is 2 hours. * The bioavailability is %

Pharmacodynamics : * Mechanism of Action : Smooth muscle cells and cardiac cells need calcium to contract. Nifedipine is a calcium ion influx inhibitor preventing it from entering the cells so relaxation results.

* Effect : In Angina : It dilates coronary arteries and increases myocardial oxygen delivery. So, the condition gets better. In Hypertension : The reduction in calcium influx by nifedipine causes arterial vasodilation and decreases peripheral vascular resistance which results in reduced arterial blood pressure.

Uses: Major : * Angina. * Hypertension. Minor : * Migraine headache. * Raynaud’s syndrome. * Congestive heart failure. * Preterm labour.

Recommended Dose : The usual starting dose is 10 milligrams, 3 times a day. Doses can be increased according to patients needs but doses above 120 milligrams per day are not recommended. N.B. If you miss a dose take it as soon as you remember it. If it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Never take double dose.

Adverse Effects : Common : * Edema. * Headache. Less Likely : * Chest pain. * Diarrhea. * Rhinitis. * Urinary frequency. * Arthralgia.

Contraindications : * Known hypersensitivity reaction to nifedine. * History of myocardial infarction. * In pregnant and nursing mothers. * Severe gastrointestinal narrowing. * Hepatic dysfunction.

Precautions : * Hypotension. * Periphral edema. * Over 65 years. * Heart, liver or kidney diseases.

Drug Interactions : 1- Grapefruit Juice : * Increases the bioavailability of nifedipine and the volume of distribution. * It causes a delay gastric emptying.  Interferes with nifedipine metabolism.

2- Antifungal Drugs : (eg. Ketoconazole) Are CYTP450 inhibitors and can inhibit the metabolism of nifedipine ( increase its level) 3-Antitubercular Drugs : (eg. Rifapentine) An inducer of CYTP450 and can induce the metabolism of nifedipine (decrease its level) 2 & 3  Adjust the dose