Impact of Increased Gastric pH on the Pharmacokinetics of Evacetrapib in Healthy Subjects

Effect of Omeprazole Administration on the Pharmacokinetics of Oral Extended-Release Nifedipine in Healthy Subjects

Oral extended-release (ER) dosage forms have been used to sustain blood drug levels, reduce adverse events, and improve patient compliance. We investigated potential effects of comedication on pharmacokinetic exposure of nifedipine ER products with different formulation designs and manufacturing processes. A clinical study compared a generic version of nifedipine ER tablet with pH-dependent dissolution behavior with an osmotic pump product with pH independent drug release under fasting condition. In this study, two nifedipine tablet products were tested with or without short-term omeprazole comedication in healthy subjects. Seven-day administration of omeprazole before nifedipine dosing significantly increased the gastric pH, and subsequently increased the geometric least square (LS) means of area under the concentration-time curve from time zero to the last measurable timepoint (AUC0-t ) and maximum plasma concentration (Cmax ) of nifedipine to 132.6% (90% confidence interval (CI): 120.6-145.7%) and 112.8% (90% CI: 100.8-126.3%) for pH-dependent ER tablets, and 120.6% (90% CI: 109.7-132.5%) and 122.5% (90% CI: 113.7-131.9%) for the pH-independent ER tablets, respectively. Similar extent of increase in AUC0-t and Cmax was confirmed in the subpopulations whose gastric pH was ≥ 4 or ≤ 3 in subjects with or without omeprazole administration. Given that similar increases in drug exposures were observed for both pH-dependent and pH-independent nifedipine formulations and the geometric LS mean ratios were between 112% and 133% with and without short-term omeprazole comedication, the gastric pH may have limited effects on omeprazole-induced nifedipine PK changes on the tested formulations. The inhibition of cytochrome P450 3A4 activity may play a significant role causing nifedipine exposure changes for both formulations, which would warrant additional assessment.

Biorelevant in vitro Tools and in silico Modeling to Assess pH-Dependent Drug-drug Interactions for Salts of Weak Acids: Case Example Potassium Raltegravir

BACKGROUND

Early assessment of pH-dependent drug-drug-interactions (DDIs) for salts of poorly soluble weakly acidic compounds offers various advantages for patient safety, the pharmaceutical industry, and regulatory bodies. Biorelevant media and tests reflecting physiological changes during acid-reducing agent (ARA) co-administration can be used to explore and predict the extent of the pH effect during therapy with ARAs.

METHODS

Solubility, one-stage and two-stage dissolution of tablets containing potassium raltegravir, the marketed salt form of this poorly soluble, weakly acidic drug, was investigated using biorelevant media specially designed to reflect administration without and during ARA co-therapy. The dissolution data were then converted into parameters suitable for input into an in silico model (Simcyp™) and the simulated plasma profiles were compared with available pharmacokinetic (PK) data from the literature.

RESULTS

Dissolution of the potassium raltegravir formulation in media reflecting ARA co-administration, and thus elevated gastric pH, was faster and more complete than in experiments reflecting the low gastric pH observed in the absence of ARA co-administration. Simulations using data from dissolution experiments with ARA media appropriately bracketed the in vivo data for ARA co-administration in healthy volunteers.

CONCLUSION

Dissolution data from in vitro experiments in biorelevant media reflecting physiological changes due to ARA co-administration provide valuable information about potassium raltegravir's behavior during concomitant ARA therapy. The approach may also be suitable for salts forms of other poorly soluble, weakly acidic drugs.

Present therapeutic role of cholesteryl ester transfer protein inhibitors

Therapeutic interventions aimed at increasing high-density lipoprotein (HDL) levels in order to reduce the residual cardiovascular (CV) risk of optimally drug treated patients have not provided convincing results, so far. Transfer of cholesterol from extrahepatic tissues to the liver appears to be the major atheroprotective function of HDL, and an elevation of HDL levels could represent an effective strategy. Inhibition of the cholesteryl ester transfer protein (CETP), raising HDL-cholesterol (HDL-C) and apolipoprotein A-I (apoA-I) levels, reduces low-density lipoprotein-cholesterol (LDL-C) and apoB levels, thus offering a promising approach. Despite the beneficial influence on cholesterol metabolism, off-target effects and lack of reduction in CV events and mortality (with torcetrapib, dalcetrapib and evacetrapib) highlighted the complex mechanism of CETP inhibition. After the failure of the above mentioned inhibitors in phase III clinical development, possibly due to the short duration of the trials masking benefit, the secondary prevention REVEAL trial has recently shown that the inhibitor anacetrapib significantly raised HDL-C (+104%), reduced LDL-C (-18%), with a protective effect on major coronary events (RR, 0.91; 95%CI, 0.85-0.97; p = 0.004). Whether LDL-C lowering fully accounts for the CV benefit or if HDL-C-rise is a crucial factor still needs to be determined, although the reduction of non-HDL (-18%) and Lp(a) (-25%), should be also taken into account. In spite of the positive results of the REVEAL Study, Merck decided not to proceed in asking regulatory approval for anacetrapib. Dalcetrapib (Dal-GenE study) and CKD-519 remain the two molecules within this area still in clinical development.