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COMPOSITION :
Nifedipine -5 Capsules
Each capsule contains Nifedipine IP 5 mg.
Nifedipine -10 Capsules
Each capsule contains Nifedipine IP 10 mg.
Nifedipine RETARD Tablets
Each film-coated slow-release tablet contains Nifedipine IP 20 mg.
PHARMACOLOGY :
Pharmacodynamics
Nifedipine is a specific and potent calcium antagonist with mainly
vascular effects.
As a specific and potent calcium antagonist, the main action of
nifedipine is to relax arterial smooth muscle both in the coronary
and peripheral circulation.
In angina pectoris, nifedipine capsules relax peripheral arteries
so reducing the load on the left ventricle. Additionally,
nifedipine dilates submaximally both clear and pre-stenotic,
stenotic and post-stenotic coronary arteries, thus protecting the
heart against coronary artery spasm and improving perfusion to the
ischaemic myocardium.
Nifedipine reduce the frequency of painful attacks and ischaemic
ECG changes, irrespective of the relative contribution from
coronary artery spasm or atherosclerosis.
Nifedipine causes a reduction in blood pressure such that the
percentage lowering is directly related to its initial level. In
normotensive individuals, nifedipine has little or no effect on
blood pressure.
Pharmacokinetics :
Nifedipine
Greater than 90% of a single oral or sub-lingual dose of
nifedipine is absorbed.
Radioactivity is detected in the serum 20 minutes after an oral
dose and 10 minutes after a sub-lingual dose. Maximal equivalent
serum concentrations are achieved 1-2 hours after enteral
administration and these correspond to the equivalent
concentrations over the same time period after intravenous
administration (the drug is almost completely absorbed).
After enteral or intravenous doses, 70-80% of activity is
eliminated (primarily as metabolites) via the urine. Remaining
excretion is via the faeces.
After 24 hours, 90% of the administered dose is eliminated.
Protein binding of nifedipine exceeds 90% in human serum.
Nifedipine RETARD
Absorption and distribution
Nifedipine is absorbed almost completely from the
gastro-intestinal tract regardless of the oral formulation used.
Protein binding of nifedipine exceeds 90% in human serum.
Metabolism and elimination
Nifedipine undergoes extensive metabolism in the liver to inactive
metabolites, with less than 1% of the parent drug appearing
unchanged in the urine. The rate of absorption determines the
drug`s apparent elimination. The apparent elimination phase
half-life for Nifedipine RETARD 20 mg tablets has been
estimated as 2.2 - 2.4 ± 0.8 hours.
INDICATIONS :
Nifedipine is indicated in the prophylaxis and treatment of
vasospastic angina and chronic stable angina, and Raynaud`s
phenomenon.
Nifedipine RETARD is indicated for the treatment of hypertension.
It may be used in combination with other antihypertensive agents.
Nifedipine RETARD is also indicated in prophylaxis of chronic
stable angina pectoris.
DOSAGE AND ADMINISTRATION :
Nifedipine capsules should be swallowed with a little fluid,
during or after food. The dosage should be established by
titration. Excessive doses can result in hypotension. Dose range
for the treatment of angina is 30 mg to 80 mg/day. The starting
dose is 5 mg thrice daily and this is gradually increased over 7
to 14 days as required. For rapid relief in angina, the capsule is
bitten and the contents retained in the mouth. Doses more than 180
mg/day is not recommended.
Nifedipine RETARD administered twice daily provides a 24-hour
control of raised blood pressure in hypertension as well as a
24-hour control of ischemia in angina pectoris. These tablets
should be swallowed whole and should not be bitten or divided.
CONTRAINDICATIONS :
Aortic stenosis, unstable angina, acute angina, acute myocardial
infarction, secondary prevention of myocardial infarction and
hypersensitivity to the drug or other dihydropyridines.
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