Clinical Drug-Drug Interaction Potential of BFE1224, Prodrug of Antifungal Ravuconazole, Using Two Types of Cocktails in Healthy Subjects

BFE1224, prodrug of ravuconazole, is a novel, once-daily, oral, triazole antifungal drug, and currently in development for the treatment of onychomycosis. The clinical drug-drug interaction (DDI) potential of BFE1224 with cytochrome P450 (CYP) and transporter was assessed by using two types of cocktails in healthy subjects in separate clinical studies. The CYP and transporter cocktails consisted of caffeine/tolbutamide/omeprazole/dextromethorphan/midazolam used in study 1 and digoxin/rosuvastatin used in study 2. In addition, repaglinide was separately administered to the same subjects in study 2. There were no major effects on the pharmacokinetics of CYP and transporter substrates, except for an approximate threefold increase in midazolam exposure after oral administration of BFE1224. The clinical DDIs of BFE1224 were mild for CYP3A and minor for other major CYPs (CYP1A2/2C8/2C9/2C19/2D6) as well as those of P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), organic anion transporting polypeptide (OATP) 1B1, and OATP1B3.

Pharmacokinetic/ pharmacodynamic evaluation of anti-infective agents

Pharmacokinetic/pharmacodynamic modeling has become an extremely important tool in evaluating and optimizing anti-infective therapy. By systematically linking the pharmacokinetic and pharmacodynamic properties of the anti-infective agent, it is possible to make educated decisions about the correct drug to be used, correct dosing regimen and to estimate the probability of success with the selected dose regimen. This article gives an overview of the current pharmacokinetic/pharmacodynamic approaches for anti-infective agents and discusses their use in optimizing drug therapy.

A transcellular assay to assess the P-gp inhibition in early stage of drug development

To provide a fast assessment in predicting P-gp-mediated DDI risk during early stage of drug development, a transcellular P-gp inhibition assay using two concentrations is presented in the present study. The efflux ratios of loperamide in the presence of forty-five commercial compounds at two concentrations were measured and compared to that of six concentrations in human P-gp cDNA-expressing LLC-PK1 cells (LLC-MDR1). The inhibition potency calculated from the change on the efflux ratio (ER) and on the net secretory flux (NSF) of loperamide was investigated. The P-gp inhibition potency was defined as potent (IC50 < 1 µM), moderate (1 µM < IC50 < 10 µM), or weak (IC50 > 10 µM). The results using 1 µM and 10 µM of inhibitor concentrations provided the best correlation and are most consistent with those generated from a 6-point approach.

Effect of Simulated Microgravity on the Disposition and Tissue Penetration of Ciprofloxacin in Healthy Volunteers

This study evaluated the effects of simulated microgravity (smuG) on the pharmacokinetics of ciprofloxacin. Six healthy volunteers participated in a crossover study to compare the pharmacokinetics of ciprofloxacin after a single 250-mg oral dose in normal gravity (1G) and smuG. Plasma and urine samples were collected, and in vivo microdialysis was employed to obtain the free interstitial concentrations in the thigh muscle. Tissue penetration (f) was determined as the ratio of the free tissue area under the concentration versus time curve (AUC(tiss,free))/AUC(plasma,free). Plasma and free interstitial ciprofloxacin concentrations were simultaneously fit to a 1-compartment body model after correction for protein binding and tissue penetration. Total and free plasma concentrations were very similar in smuG and 1G. Tissue penetration in smuG (f =0.61 +/- 0.36) was slightly lower than in 1G (f =0.92 +/- 0.63); however, the difference was not significant. The authors conclude that the disposition of ciprofloxacin was not affected by simulated microgravity.

Pharmacokinetic/Pharmacodynamic (PK/PD) Evaluation of a Once-Daily Treatment Using Ciprofloxacin in an Extended-Release Dosage Form*

OBJECTIVE

To evaluate the suitability of a once-a-day dosing regimen of ciprofloxacin using a new extended-release dosage form based on PK/PD principles.

METHODS

Ciprofloxacin's serum concentrations were measured after administration of 500 mg immediate-release twice-daily, and 1,000 mg extended-release once-daily to 19 healthy volunteers. Pharmacokinetic parameters were determined using non-compartmental and compartmental data analysis. Measured serum concentration profiles were linked to ciprofloxacin's effect against Escherichia coli (MIC 0.013 mg/l) from in vitro kill curve studies where the pharmacokinetics of ciprofloxacin were simulated and change in number of bacteria (CFU/ml) versus time was monitored. Resulting parameters were used to compare expected kill curves for the two dosing regimens based on measured ciprofloxacin concentrations.

RESULTS

Fitting the data using an appropriate PK/PD model resulted in a set of mean pharmacodynamic parameters (bacterial growth rate constant, k0, maximum kill rate constant, Kmax, and EC50). The model included a novel term to account for a change in kill rate after approximately 4 h when Kmax decreased in concentration-dependent matter. The model allowed excellent curve fits of all ciprofloxacin concentrations investigated. Comparison of expected kill curves with the immediate-release versus extended-release treatments showed similar outcome. Both treatments resulted in a decrease in CFU/ml > 5 log units over 24 h.

CONCLUSION

Results indicate that once-a-day dosing of equal total daily doses with the new and more compliance-friendly extended-release dosing form will be therapeutically equivalent to once-a-day dosing with traditional immediate-release dosage forms for treatment of infections with this microorganism.

Physiological, pharmacokinetic, and pharmacodynamic changes in space

Medications have been taken since the first Mercury flight in 1967 and, since then, have been used for several indications such as space motion sickness, sleeplessness, headache, nausea, vomiting, back pain, and congestion. As the duration of space missions get longer, it is even more likely that astronauts will encounter some of the acute illnesses that are frequently seen on Earth. Microgravity environment induces several physiological changes in the human body. These changes include cardiovascular degeneration, bone decalcification, decreased plasma volume, blood flow, lymphocyte and eosinophil levels, altered hormonal and electrolyte levels, muscle atrophy, decreased blood cell mass, increased immunoglobulin A and M levels, and a decrease in the amount of microsomal P-450 and the activity of some of its dependent enzymes. These changes may be expected to have severe implications on the pharmacokinetic and pharmacodynamic properties of drug substances.