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CALCIUM CHANNEL BLOCKERS : PROPERTIES
Three calcium channel blockers are presently available in
the USA: diltiazem, nifedipine, and verapamil. Their major in-
dication is in the treatment of angina.
Pharmacokinetics (dosage forms )
* Absorption: All 3 agents are well absorbed from the gut.
Nifedipine is also rapidly absorbed from the buccal mucosa.
* Elimination: Nifedipine and verapamil are excreted primarily
by the kidneys into the urine; diltiazem and its metabolites
appear in the feces.
Other Indications of the Calcium Channel Blockers
* Arrhythmias: Verapamil is labeled for use in supraventricular
arrhythmias (see Chapter 3).
* Hypertension: Verapamil has recently been approved for use in
hypertension. Nifedipine and diltiazem are also useful (but
at present unlabeled) in hypertension (see Chapter 5).
(PgDn key for more text)
* Hypertrophic cardiomyopathy (unlabeled): Verapamil is fre-
quently useful. Nifedipine and diltiazem are also effective
in selected patients.
* Other indications (unlabeled): Nifedipine is effective in the
treatment of some cases of Raynaud's phenomenon. Verapamil
has been used to treat insulinoma-induced hypoglycemia.
* Hypersensitivity: (uncommon)
* CV: verapamil and diltiazem are contraindicated in sick sinus
syndrome or AV conduction defect (in the absence of a
pacemaker), and in severe hypotension as in cardiogenic
shock. Warning: Congestive heart failure may be worsened by
verapamil or diltiazem.
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