Nifedipine increases and glyceryl trinitrate decreases apparent liver blood flow in normal subjects.

Abstract

The effects of sublingual nifedipine (10 mg) and of glyceryl trinitrate (500 ,g), which produce arterial and venous vasodilatation respectively, on indocyanine green estimated apparent liver blood flow (LBF) were studied in six healthy volunteers. Nifedipine significantly increased (33 + 12%; mean + s.e. mean) and glyceryl trinitrate significantly reduced (18 + 3%) LBF. There was a positive relationship (r = 0.92, P < 0.05) between the reduction in mean arterial pressure produced by nifedipine and the percentage increase in LBF. These results show that single doses of nifedipine and glyceryl trinitrate significantly alter LBF.

The influence of captopril, the nitrates and propranolol on apparent liver blood flow.

“…Both propranolol and glyceryl trinitrate produced a marked reduction in apparent liver blood flow consistent with the findings from other studies in normal subjects (Feely, 1984;Feely et al, 1981).…”

“…Propranolol (Feely et al, 1981), prazosin and hydralazine (Magorien et al, 1981), glyceryl trinitrate and nifedipine (Feely, 1984), have all been evaluated recently for their ability to influence liver blood flow and, in the case of propranolol, portal hypertension.…”

The trans‐hepatic extraction of nifedipine.

“…The liver plasma flows measured in the present study are close to the values reported after nifedipine by Feely (1984) when his data are recalculated using 80% hepatic extraction for ICG, as observed in the current study, rather than 100%. Surprisingly, the hepatic clearance accounted for only 64.9% of total body clearance, suggesting that significant metabolism occurs outside the liver.…”

The influence of posture on the pharmacokinetics of orally administered nifedipine.

“…Nifedipine increases liver blood flow following a single oral dose (Feely, 1984), and it is possible that the effect of posture on the AUC of nifedipine could be related to the presence of higher plasma drug concentrations in the portal vasculature following its more rapid absorption on the right side or standing. This could have resulted in a greater nifedipine-induced increase in hepatic blood flow during the absorption phase and caused a lowering of its extraction ratio and an increase in bioavailability.…”