Effects of diltiazem on morphine-induced respiratory decline.

The individual and combined effects of subcutaneous morphine and diltiazem, a calcium channel inhibitor, on arterial blood gases and pH were assessed in conscious Fischer-344 rats. Morphine (4 mg kg-1) produced hypercapnia, hypoxia and slight acidosis, as compared with control values. Diltiazem (10 mg kg-1) alone did not affect these parameters; however, it significantly delayed the onset of the aforementioned effects of morphine.