Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2019 Publisher: Aventis Pharma Limited, One Onslow Street, Guildford, Surrey, GU1 4YS, UK or trading as: Sanofi-aventis or Sanofi, One Onslow Street, Guildford, Surrey, GU1 4YS, UK
Pharmacotherapeutic group: Calcium channel blockers; Benzothiazepine derivatives
ATC code: C08DB01
Tildiem is a calcium antagonist. It restricts the slow channel entry of calcium into the cell and so reduces the liberation of calcium from stores in the sarcoplasmic reticulum. This results in a reduction of the amount of available intracellular calcium reducing myocardial oxygen consumption. It increases exercise capacity and improves all indices of myocardial ischaemia in the angina patient. Tildiem relaxes large and small coronary arteries and relieves the spasm of vasospastic (prinzmetals) angina and the response to catecholamines but has little effect on the peripheral vasculature. There is therefore no possibility of reflex tachycardia. A small reduction in heart rate occurs which is accompanied by an increase in cardiac output, improved myocardial perfusion and reduction of ventricular work. In animal studies, Tildiem protects the myocardium against the effects of ischaemia and reduces the damage produced by excessive entry of calcium into the myocardial cell during reperfusion.
Diltiazem hydrochloride is effective in angina, protecting the heart against ischaemia, vasodilating coronary arteries and reducing myocardial oxygen requirements. It is well tolerated and does not generally give rise to side effects associated with peripheral vasodilators, nor cause significant myocardial depression.
Diltiazem is well absorbed (90%) in healthy volunteers following oral administration.
Peak plasma concentrations occur 3 to 4 hours after dosing.
Due to a first pass effect, the bioavailability of the 60 mg tablet is about 40%. The mean apparent plasma half-life is 4-8 hours.
Diltiazem is 80 to 85% bound to plasma proteins. It is extensively metabolised by the liver.
The major circulating metabolite, N-monodesmethyl diltiazem accounts for approximately 35% of the circulating diltiazem.
Less than 5% of diltiazem is excreted unchanged in the urine.
There is a linear relationship between dose and plasma concentration. During long term administration to any one patient, plasma concentrations of diltiazem remain constant.
Mean plasma concentrations in elderly subjects and patients with renal and hepatic insufficiency are higher than in young subjects.
Diltiazem and its metabolites are poorly dialysed.
Reproduction studies have been conducted in mice, rats, and rabbits. Administration of doses ranging from 4 to 6 times (depending on species) the upper limit of the optimum dosage range in clinical trials (480 mg q.d. or 8 mg/kg q.d. for a 60-kg patient) resulted in embryo and fetal lethality. These studies revealed, in one species or another, a propensity to cause fetal abnormalities of the skeleton, heart, retina, and tongue. Also observed were reductions in early individual pup weights, pup survival, as well as prolonged delivery times and an increased incidence of stillbirths.
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