Editing Diltiazem Hydrochloride (section)

==Pharmacokinetics==
<u>Absorption</u>

Diltiazem is almost completely absorbed from the gastrointestinal tract after oral doses, but undergoes extensive first-pass hepatic metabolism resulting in a bioavailability of about 40%.

Peak plasma concentrations occur about 3 to 8 hours after an oral dose, depending on the dosage form

<u>Distribution</u>

Diltiazem is about 80% bound to plasma proteins. It is distributed into breast milk.

<u>Metabolism</u>

It is extensively metabolized in the liver, mainly by the cytochrome P450 isoenzyme CYP3A4. 

<u>Elimination</u>

The half-life of diltiazem is reported to be about 3 to 8 hours, again depending on the dosage form. 
About 2 to 4% of a dose is excreted in urine as unchanged diltiazem with the remainder excreted as metabolites in bile and urine.