Nifedpine

Characterisation of indomethacin and nifedipine using variable‐temperature solid‐state NMR

“…Approximately, 20 000 transients were accumulated in each case, with a pulse angle of 90°and a recycle delay of 1 s. Full assignments were made via proton spectra using HETCOR experiments. The solution-state indomethacin and nifedipine 13 C chemical shifts and assignments are consistent with the work of O'Brien et al 13 and that of Ali 31 respectively, except that in the former case we have exchanged the assignments for C-2 and C-4.…”

Grapefruit juice-nifedipine interaction: possible involvement of several mechanisms

“…The absence of double peaks in the plasma profiles in the water treatment group tends to rule out enterohepatic circulation. With a p K a value of −0·9 (20), NIF exists in its unprotonated form at all pH values in the GI tract and thus pH‐dependent solubility and absorption can be ruled out. The existence of absorption windows for NIF can also be ruled out as the drug is well absorbed throughout the upper and lower intestine in humans (21).…”

Grapefruit juice and orange juice effects on the bioavailability of nifedipine in the rat

“…As well, nifedipine is rapidly, extensively, and presumably irreversibly metabolized via oxidation in the rat, with the principal metabolite further metabolized to several other biotransformation products which themselves can undergo enterohepatic circulation [34,35]. Given that the pK a -value of nifedipine is − 0.9 [55], the drug exists primarily in its unprotonated form at all pH conditions in the GI tract and thus pH-dependent solubility and absorption can be ruled out. The existence of specific sites of absorption ('absorption windows') for nifedipine can also be ruled out since the drug is well absorbed (\ 90%) throughout the upper and lower intestine in both rats and man [36,47,56], although differences in the extent of gut wall metabolism in different regions of the gut could contribute, in part, to the observed double-peak effect [47].…”