When used as monotherapy, reasonable starting doses are 180 to 240 mg once daily, although some patients may respond to lower doses. Maximum antihypertensive effect is usually observed by 14 days of chronic therapy; therefore, dosage adjustments should be scheduled accordingly. The usual dosage range studied in clinical trials was 240 to 360 mg once daily. Individual patients may respond to higher doses of up to 480 mg once daily. Dosages for the treatment of angina should be adjusted to each patient's needs, starting with a dose of 120 or 180 mg once daily. Individual patients may respond to higher doses of up to 480 mg once daily. When necessary, titration may be carried out over a 7- to 14-day period.

Tissue homogenate of cerebral cortext and heart containing calcium channel receptors was used in a radioligand-binding assays. Cerebral cortices of male SD rats were homogenized. Hearts were also removed, perfused through aorta with ice-cold saline solution, and homogenized. Subsequently, the cardiac homogenates were filtered through four layers of cloth. Both cortical and cardiac homogenates were washed 5 times by centrifugation for 10 min at 48000 g. The final pelle was resuspended to a conc. of 50 mg of original wet tissue wt/mL of buffer and stored at -70°C. Tissue homogenate (200 uL) was incubated for 90 min in a dark room at 0°C with 100 uL of [3H]nitreddipine (3x10^-10M, 87 Ci/mmol) and 100 uL of the test compound dissolved in DMSO in 50 mM of Na-Hepes buffer, pH 7.4. The incubations were stopped by adding 4 mL of cold buffer followed by rapid filtratoin through glass fiber filter disks. The samples were subsequently washed 3 times with 4.5 mL of the same buffer and placed into scintill. vials. Diltiazem inhibited binding of [3H]nitrendipine with Ki of 21 nM.