As noted above (CLINICAL PHARMACOLOGY) careful studies with other formulations of nitroglycerin have shown that maintenance of continuous 24-hour plasma levels of nitroglycerin results in tolerance (i.e., loss of clinical response). Every dosing regimen for Nitroglycerin Extended-Release Capsules should provide a daily nitrate-free interval to avoid the development of this tolerance. The minimum necessary length of such an interval has not been defined, but studies with other nitroglycerin formulations have shown that 10 to 12 hours is sufficient. Large controlled studies with other formulations of nitroglycerin show that no dosing regimen with Nitroglycerin Extended-Release Capsules should be expected to provide more than about 12 hours of continuous anti-anginal efficacy per day.
The pharmacokinetics of Nitroglycerin capsules, and the clinical effects of multiple-dose regimens, have not been well studied. In clinical trials, the initial regimen of Nitroglycerin has been 2.5 to 6.5 mg three to four times a day, with subsequent upward dose adjustment guided by symptoms and side effects. In one trial, 5 of the 18 subjects were titrated up to a dose of 26 mg four times a day.