Studies on the bioavailability of glyceryl trinitrate after sublingual administration of spray and tablet

The plasma profiles of nitroglycerin (glyceryl trinitrate, GTN, CAS 55-63-0) were estimated after two sublingual puffs of 0.4 mg GTN from a fluorochlorohydrocarbon (FCH)-free oral spray and one sublingual tablet of 0.5 mg GTN (Nitromex). The study was carried out in an open, randomized, two-phase, cross-over design with 24 volunteers. Eighteen blood samples were taken within 30 minutes after administration, and the plasma concentrations of GTN were determined by a specific gas chromatographic method with electron capture detection. The pharmacokinetic parameters, Cmax, tmax, and AUC, were determined for each volunteer. After correction of the AUC and Cmax values of the oral spray by dividing by two, the ratios (spray/tablet) of the AUC and Cmax and the 90% confidence intervals were estimated. The plasma concentrations of GTN (mean) after the spray (dose: 0.8 mg GTN) reached a maximum of 3.96 ng/ml (range: 0.99-10.86) at 3.5 minutes (range: 2-5). The plasma concentrations of GTN (mean) after the tablet (dose: 0.5 mg GTN) reached a maximum of 1.97 ng/ml (range: 0.57-4.33) at 4.9 minutes (range: 3-7). The corrected ratios (spray/tablet) of AUC and Cmax were 1.02 and 0.97 with the 90% confidence intervals (0.80, 1.30), respectively (0.77, 1.24). The results indicate that the oral spray in a dose of 0.4 mg is equivalent to the sublingual tablet in a dose of 0.5 mg.