Evaluation of the pharmacokinetic interaction after multiple oral doses of linagliptin and digoxin in healthy volunteers.

The aim of this study was to investigate whether multiple doses of the oral and highly selective dipeptidyl peptidase-4 inhibitor linagliptin affect the steady-state pharmacokinetics of the P-glycoprotein substrate digoxin. This single-center, open-label, two-period cross-over study involved healthy subjects (n = 20), randomized to treatment sequence AB or BA, where A comprised 0.25 mg digoxin qd for 5 days, then 0.25 mg digoxin qd plus 5 mg linagliptin qd for 6 days, and B comprised 0.25 mg digoxin qd for 11 days. A treatment-free period (≥35 days for AB and 14 days for BA) separated each treatment in both sequences. There were no clinically significant changes in steady-state pharmacokinetic parameters of digoxin when it was co-administered with linagliptin. The ratio of the adjusted-by-treatment geometric mean ratios and associated 90% confidence intervals for the AUC(τ,ss), C (max,ss) and renal clearance (CL( R,0-24,ss)) of digoxin were all within the bioequivalence range 80-125%, which is important as digoxin has a narrow therapeutic range. There was a low incidence of adverse events, which were randomly distributed between treatment groups. In conclusion, linagliptin did not alter the pharmacokinetics of digoxin in this study, indicating that linagliptin does not inhibit P-glycoprotein or other transporters relevant for digoxin pharmacokinetics. These results suggest that linagliptin and digoxin can be co-administered without dose adjustment. Administration of digoxin alone and with linagliptin was well tolerated.

Bioavailability investigation of a new tilidine/naloxone liquid formulation compared to a reference formulation.

An oral solution available as ethanol-free droplets of the fixed drug combination tilidine-HCl 50 mg/naloxone-HCl 4 mg (CAS 27107-79-5 and CAS 465-65-6, respectively; Tilidin-ratiopharm plus Tropfen) was investigated in 12 healthy volunteers together with an ethanol-containing reference preparation for comparable bioavailability. The study was conducted in an open, randomized, two-way cross-over design applying single doses of 20 droplets (equivalent to 50 mg tilidine-HCl/4 mg naloxone-HCl) of either formulation in the fasting state. The drug plasma profiles were monitored for a period of 48 h by means of LC-MS/MS for tilidine and its active metabolite nortilidine, whereas GC-MS was employed in order to determine naloxone and its phase I metabolite, 6-beta-naloxole. Maximum concentrations (Cmax) achieved were 22.28 ng/ml (tilidine) and 92.78 ng/ml (nortilidine) for the test preparation. Corresponding values for the reference preparation were 24.95 ng/ml (tilidine) and 100.73 ng/ml (nortilidine). The extent of drug absorption (AUC0-infinity) amounted to 38.83 ng h/ml and 467.63 ng h/ml for the prodrug tilidine and the metabolite nortilidine of the test preparation and corresponded well to 43.81 ng h/ml and 493.85 ng h/ml of the reference. Regarding the rate of drug absorption, essentially identical tmax and Rabs values for both tilidine and nortilidine of either preparation in addition pointed to well comparable liquid formulations and equipotent analgesia may be inferred from opioid pharmakokinetic profiles. Pharmacokinetics of the opioid antagonist naloxone and 6-beta-naloxole were also determined and resulted in well coinciding profiles for both preparations. Thus despite the fact that only minimum oral naloxone bioavailabilities were observed, plasma level monitoring of naloxone and 6-beta-naloxole allowed for demonstration of systemic exposure of opioid antagonistic compounds throughout a period of 2-3 h after oral drug administration. Due to the limited number of subjects involved, the primary aim of the study did not consist in demonstration of drug bioequivalence. Rather a comparable bioavailability between preparations was assumed if AUC and Cmax point estimators of 90% confidence intervals would be contained within a 0.80-1.20 range. The study outcome revealed that all four investigated analytes met this requirement, whilst nortilidine pharmacokinetic parameters even fulfilled commonly accepted bioequivalence criteria, i.e. inclusion of 90% confidence intervals of AUC- and Cmax-ratios within acceptance limits of 80% and 125%. Increased data variation observed with bioavailability parameters of tilidine, naloxone and 6-beta-naloxole prevented their bioequivalence demonstration based on only 12 study participants. In conclusion, single doses of two different tilidine/naloxone 50 mg/4 mg liquid formulations revealed well comparable bioavailability for all 4 analytes investigated. Both treatments were fairly well tolerated. Most frequently reported adverse events were dizziness, headache and nausea, which all recovered without sequelae and necessity of concomitant treatment.

Pharmacokinetic drug interaction studies with candesartan cilexetil.

The aim of this series of studies was to determine the potential for pharmacokinetic interaction between candesartan (administered orally as the prodrug candesartan cilexetil) and hydrochlorothiazide (HCTZ), nifedipine, glibenclamide, warfarin, digoxin or the components of an oral contraceptive formulation. All studies were performed in healthy volunteers using randomised, crossover or add-on study designs. Candesartan cilexetil was administered orally at doses of 8, 12 or 16 mg. The pharmacokinetic parameters were determined for comparator agents and candesartan following administration of each agent alone or in combination. There were no changes in the drug plasma concentrations of nifedipine, glibenclamide, digoxin or oral contraceptives when co-administered with candesartan cilexetil. Co-administration of candesartan cilexetil caused a slight but significant decrease in the AUC of HCTZ. However, the 90% confidence intervals (CI) for AUC ratios for HCTZ when co-administered with candesartan cilexetil were within the defined limits of bioequivalence. Candesartan cilexetil produced a 7% decrease in trough plasma warfarin concentration but this had no effect on prothrombin time. Co-administration of candesartan cilexetil with HCTZ produced a statistically significant increase in the bioavailability and Cmax values for candesartan (18% and 25%, respectively). However, this increase is not considered to be clinically relevant. No other co-administered drug (nifedipine, glibenclamide, digoxin, oral contraceptive) affected the pharmacokinetic parameters of candesartan. Candesartan cilexetil was well tolerated both alone and in combination with the other agents.

Lansoprazole does not affect the bioavailability of oral contraceptives.

The effects of the proton pump inhibitor lansoprazole on the bioavailability of a low-dose oral contraceptive (OC), containing 0.03 mg ethinyloestradiol (EE) and 0.15 mg levonorgestrel (LNG), were investigated. Twenty-four healthy females (aged 19-35 years; weight 60.6 +/- 7.1 kg) participated in a multiple-dose, placebo-controlled, randomized two-way cross-over study. All subjects received the OC over 2 full menstrual cycles from day 1 to day 21 separated by a drug-free interval of 7 days. Lansoprazole (60 mg day-1) or placebo was coadministered for 3 weeks each. Plasma concentrations of EE and LNG were determined by GC-MS. The 90% confidence intervals for ratios of Cmax and AUC after log transformation of both EE and LNG ranged between 91 and 111%, indicating that lansoprazole did not affect the bioavailability of EE and LNG.

PIP: The research reported in this paper assessed the effects of the proton pump inhibitor lansoprazole on the bioavailability of a low-dose oral contraceptive (OC) containing 0.03 mg ethinyl estradiol (EE) and 0.15 mg levonorgestrel (LNG). Blood plasma concentrations of lansoprazole, EE, LNG, and several hormones were measured following a two-way, cross-over study design. 24 German women in good health were used in this study. All subjects received physical examinations, complete laboratory work-ups, and were found normal. All women received the OC over two complete menstrual cycles from days 1 to 21, with the remaining 7 days being drug-free. 60 mg per day of lansoprazole or a placebo were given for 21 days with the OC. Plasma was assayed by capillary column gas chromatography with mass spectrometry. Urine was also collected and analyzed. The results showed that the 24 women did not experience any significant change or alteration in plasma EE and LNG levels.