Alteration in the disposition and metabolism of S(-)-propranolol in rats with active respiratory viral infection

Examination of Urinary Excretion of Unchanged Drug in Humans and Preclinical Animal Models: Increasing the Predictability of Poor Metabolism in Humans

PURPOSE

A dataset of fraction excreted unchanged in the urine (fe) values was developed and used to evaluate the ability of preclinical animal species to predict high urinary excretion, and corresponding poor metabolism, in humans.

METHODS

A literature review of fe values in rats, dogs, and monkeys was conducted for all Biopharmaceutics Drug Disposition Classification System (BDDCS) Class 3 and 4 drugs (n=352) and a set of Class 1 and 2 drugs (n=80). The final dataset consisted of 202 total fe values for 135 unique drugs. Human and animal data were compared through correlations, two-fold analysis, and binary classifications of high (fe ≥30%) versus low (<30%) urinary excretion in humans. Receiver Operating Characteristic curves were plotted to optimize animal fe thresholds.

RESULTS

Significant correlations were found between fe values for each animal species and human fe (p<0.05). Sixty-five percent of all fe values were within two-fold of human fe with animals more likely to underpredict human urinary excretion as opposed to overpredict. Dogs were the most reliable predictors of human fe of the three animal species examined with 72% of fe values within two-fold of human fe and the greatest accuracy in predicting human fe ≥30%. ROC determined thresholds of ≥25% in rats, ≥19% in dogs, and ≥10% in monkeys had improved accuracies in predicting human fe of ≥30%.

CONCLUSIONS

Drugs with high urinary excretion in animals are likely to have high urinary excretion in humans. Animal models tend to underpredict the urinary excretion of unchanged drug in humans.

Pharmacokinetics of D-propranolol following oral, intra-arterial and intraportal administration: contrasting effects of oral glucose pretreatment

Several research groups have reported that in man the oral administration of propranolol with food leads to a marked increase (about 50 per cent) in the area under the plasma concentration-time curve (AUCpo) of this well absorbed and highly metabolized drug. An acute change in hepatic metabolic enzyme activity has been postulated as one of the mechanisms which could be responsible for this observed 'food effect'. The administration of simple carbohydrates such as glucose and fructose has been documented to influence hepatic drug metabolism. Therefore, in the present study, the effect of oral glucose (4 g kg-1 as a 50 per cent aqueous solution) on the disposition kinetics of d-propranolol was examined in male Sprague-Dawley rats (8 to 9 per group). Oral glucose treatment caused a statistically significant decrease (50.4 +/- 12.3 vs 36.6 +/- 15.2 min micrograms ml-1; p < 0.05) in the AUCpo of propranolol when this drug was given by oral intubation (10 mg kg-1). This glucose treatment also caused the apparent mean residence time of propranolol after an oral dose to increase from 0.70 +/- 0.08 h to 1.79 +/- 0.29 h (p < 0.05), but did not change its rate of elimination (suggesting collectively a decreased apparent intrinsic clearance and prolonged drug absorption). In a second study, the same oral glucose treatment was demonstrated to have little impact on the steady state concentrations of propranolol when this drug was infused intraarterially at a constant rate. This confirms that the systemic clearance of propranolol is influenced minimally by the glucose treatment. In a third study, propranolol was infused at a constant rate into the portal vein (pyloric vein infusion) bypassing the processes of intestinal metabolism and absorption (i.e. to remove these sources of variability associated with oral administration). Under these conditions, no significant changes in AUC or apparent mean residence time were observed for the two propranolol doses studied (10 mg kg-1 and 5 mg kg-1). We conclude that the oral glucose and oral propranolol interaction appears to be due to an alteration in the input process before drug enters the liver. Furthermore, this experimental series suggests that studies combining accurate assessments of systemic clearance (constant rate intra-arterial infusion studies), intrinsic hepatic clearance (pyloric vein infusion studies), and oral administration supplemented with necessary protein binding studies may be used together to characterize the mechanism responsible for drug-nutrient and drug-drug interactions.