This study characterized single-and multiple-dose pharmacokinetics of canagliflozin and its O-glucuronide metabolites (M5 and M7) and pharmacodynamics (renal threshold for glucose [RT G ], urinary glucose excretion ], and 24-hour mean plasma glucose ]) of canagliflozin in subjects with type 2 diabetes. Thirty-six randomized subjects received canagliflozin 50, 100, or 300 mg/day or placebo for 7 days. On Days 1 and 7, area under the plasma concentration-time curve and maximum observed plasma concentration (C max ) for canagliflozin and its metabolites increased dose-dependently. Half-life and time at which C max was observed were dose-independent. Systemic molar M5 exposure was half that of canagliflozin; M7 exposure was similar to canagliflozin. Steady-state plasma canagliflozin concentrations were reached by Day 4 in all active treatment groups. Pharmacodynamic effects were dose-and exposure-dependent. All canagliflozin doses decreased RT G , increased UGE 0-24h , and reduced MPG 0-24h versus placebo on Days 1 and 7. On Day 7, placebo-subtracted least-squares mean decreases in MPG 0-24h ranged from 42-57 mg/dL with canagliflozin treatment. Adverse events (AEs) were balanced between treatments; no treatment-related serious AEs, AE-related discontinuations, or clinically meaningful adverse changes in routine safety evaluations occurred. The observed pharmacokinetic/pharmacodynamic profile of canagliflozin in subjects with type 2 diabetes supports a once-daily dosing regimen. Keywordscanagliflozin, sodium glucose co-transporter 2 inhibitor, type 2 diabetes mellitus, pharmacokinetics, pharmacodynamicsIn humans, glucose is freely filtered through the renal glomerulus and then reabsorbed in the proximal tubules. The renal threshold for glucose (RT G ) is the plasma glucose (PG) concentration at which tubular reabsorption of glucose begins to saturate; glucose is excreted into the urine in direct proportion to the glucose concentration above this threshold. The sodium glucose co-transporter 2 (SGLT2) is responsible for the majority of filtered glucose reabsorption from the lumen. 1,2 Patients with diabetes have been shown to have elevated renal glucose reabsorption, which may contribute to persistent elevated PG concentrations. 3,4 Canagliflozin, an orally active inhibitor of SGLT2, is currently in development for the treatment of patients with type 2 diabetes mellitus. 5,6 By inhibiting SGLT2, canagliflozin inhibits glucose reabsorption in renal proximal tubular cells, thereby reducing the RT G . 7,8 In preclinical models of diabetes, canagliflozin reduces RT G , increases urinary glucose excretion (UGE), decreases PG, reduces weight gain, and improves b-cell function. 9 In a multiple-dose clinical study in healthy subjects, once-daily, orally administered canagliflozin decreased the 24-hour mean RT G and increased UGE in a dosedependent manner while 24-hour mean PG (MPG 0-24h ) levels were not affected by canagliflozin treatment. 6 Maximal lowering of the 24-hour mean RT G to approximately 60 mg/dL and in...

Topiramate is a new antiepileptic drug (AED) that has been approved worldwide (in more than 80 countries) for the treatment of various kinds of epilepsy. It is currently being evaluated for its effect in various neurological and psychiatric disorders. The pharmacokinetics of topiramate are characterised by linear pharmacokinetics over the dose range 100-800 mg, low oral clearance (22-36 mL/min), which, in monotherapy, is predominantly through renal excretion (renal clearance 10-20 mL/min), and a long half-life (19-25 hours), which is reduced when coadministered with inducing AEDs such as phenytoin, phenobarbital and carbamazepine. The absolute bioavailability, or oral availability, of topiramate is 81-95% and is not affected by food. Although topiramate is not extensively metabolised when administered in monotherapy (fraction metabolised approximately 20%), its metabolism is induced during polytherapy with carbamazepine and phenytoin, and, consequently, its fraction metabolised increases. During concomitant treatment with topiramate and carbamazepine or phenytoin, the (oral) clearance of topiramate increases 2-fold and its half-life becomes shorter by approximately 50%, which may require topiramate dosage adjustment when phenytoin or carbamazepine therapy is added or discontinued. From a pharmacokinetic standpoint, topiramate is a unique example of a drug that, because of its major renal elimination component, is not subject to drug interaction due to enzyme inhibition, but nevertheless is susceptible to clinically relevant drug interactions due to induction of its metabolism. Unlike old AEDs such as phenytoin and carbamazepine, topiramate is a mild inducer and, currently, the only interaction observed as a result of induction by topiramate is that with ethinylestradiol. Topiramate only increases the oral clearance of ethinylestradiol in an oral contraceptive at high dosages (>200 mg/day). Because of this dose-dependency, possible interactions between topiramate and oral contraceptives should be assessed according to the topiramate dosage utilised. This paper provides a critical review of the pharmacokinetic interactions of topiramate with old and new AEDs, an oral contraceptive, and the CNS-active drugs lithium, haloperidol, amitriptyline, risperidone, sumatriptan, propranolol and dihydroergotamine. At a daily dosage of 200 mg, topiramate exhibited no or little (with lithium, propranolol and the amitriptyline metabolite nortriptyline) pharmacokinetic interactions with these drugs. The results of many of these drug interaction studies with topiramate have not been published before, and are presented and discussed for the first time in this article.

The pharmacokinetics of once-daily oral levofloxacin (study A) or intravenous levofloxacin (study B) in 40 healthy male volunteers were investigated in two separate randomized, double-blind, parallel-design, placebo-controlled studies. Levofloxacin at 500 mg or placebo was administered orally or intravenously as a single dose on day 1; daily oral or intravenous dosing resumed on days 4 to 10. In a third study (study C), the comparability of the bioavailabilities of two oral and one intravenous levofloxacin formulations were investigated with 24 healthy male subjects in an open-label, randomized, three-way crossover study. Levofloxacin at 500 mg as a single tablet or an intravenous infusion was administered on day 1; following a 1-week washout period, subjects received the second regimen (i.e., the other oral formulation or the intravenous infusion); the third and final regimen was administered following a 1-week washout period. The concentrations of drug in plasma and urine were measured by validated high-pressure liquid chromatography methods. Pharmacokinetic parameters were estimated by noncompartmental methods. In both study A (oral levofloxacin) and study B (intravenous levofloxacin), steady state was attained within 48 h after the start of the multiple dosing on day 4. Levofloxacin pharmacokinetics were linear and predictable for the single and multiple 500-mg, once-daily oral and intravenous dosing regimens, and the values of the pharmacokinetic parameters for the oral and intravenous administrations were similar. Study C indicated that levofloxacin was rapidly and completely absorbed from the oral tablets, with mean times to the maximum concentration of drug in serum of approximately 1.5 h and mean absolute bioavailability of > or =99%. These results support the interchangeability of the oral and intravenous routes of levofloxacin administration.

Objective: Canagliflozin, a sodium-glucose co-transporter 2 inhibitor, approved for the treatment of type-2 diabetes mellitus (T2DM), is metabolized by uridine diphosphate-glucuronosyltransferases (UGT) 1A9 and UGT2B4, and is a substrate of P-glycoprotein (P-gp). Canagliflozin exposures may be affected by coadministration of drugs that induce (e.g., rifampin for UGT) or inhibit (e.g. probenecid for UGT; cyclosporine A for P-gp) these pathways. The primary objective of these three independent studies (single-center, open-label, fixed-sequence) was to evaluate the effects of rifampin (study 1), probenecid (study 2), and cyclosporine A (study 3) on the pharmacokinetics of canagliflozin in healthy participants. Methods: Participants received; in study 1: canagliflozin 300 mg (days 1 and 10), rifampin 600 mg (days 4 – 12); study 2: canagliflozin 300 mg (days 1 – 17), probenecid 500 mg twice daily (days 15 – 17); and study 3: canagliflozin 300 mg (days 1 – 8), cyclosporine A 400 mg (day 8). Pharmacokinetics were assessed at pre-specified intervals on days 1 and 10 (study 1); on days 14 and 17 (study 2), and on days 2 – 8 (study 3). Results: Rifampin decreased the maximum plasma canagliflozin concentration (Cmax) by 28% and its area under the curve (AUC) by 51%. Probenecid increased the Cmax by 13% and the AUC by 21%. Cyclosporine A increased the AUC by 23% but did not affect the Cmax. Conclusion: Coadministration of canagliflozin with rifampin, probenecid, and cyclosporine A was well-tolerated. No clinically meaningful interactions were observed for probenecid or cyclosporine A, while rifampin coadministration modestly reduced canagliflozin plasma concentrations and could necessitate an appropriate monitoring of glycemic control.

This investigation was designed to evaluate the single-dose pharmacokinetics of itraconazole, hydroxyitraconazole, and hydroxypropyl-␤-cyclodextrin (HP-␤-CD) after intravenous administration to children at risk for fungal infection. Thirty-three children aged 7 months to 17 years received a single dose of itraconazole (2.5 mg/kg in 0.1-g/kg HP-␤-CD) administered over 1 h by intravenous infusion. Plasma samples for the determination of the analytes of interest were drawn over 120 h and analyzed by high-pressure liquid chromatography, and the pharmacokinetics were determined by traditional noncompartmental analysis. Consistent with the role of CYP3A4 in the biotransformation of itraconazole, a substantial degree of variability was observed in the pharmacokinetics of this drug after IV administration. The maximum plasma concentrations (C max ) for itraconazole, hydroxyitraconazole, and HP-␤-CD averaged 1,015 ؎ 692 ng/ml, 293 ؎ 133 ng/ml, and 329 ؎ 200 g/ml, respectively. The total body exposures (area under the concentration-time curve from 0 to 24 h) for itraconazole, hydroxyitraconazole, and HP-␤-CD averaged 4,922 ؎ 6,784 ng ⅐ h/ml, 3,811 ؎ 2,794 ng ⅐ h/ml, and 641.5 ؎ 265.0 g ⅐ h/ml, respectively, with no significant age dependence observed among the children evaluated. Similarly, there was no relationship between age and total body clearance (702.8 ؎ 499.4 ml/h/kg); however, weak associations between age and the itraconazole distribution volume (r 2 ‫؍‬ 0.18, P ‫؍‬ 0.02), C max (r 2 ‫؍‬ 0.14, P ‫؍‬ 0.045), and terminal elimination rate (r 2 ‫؍‬ 0.26, P < 0.01) were noted. Itraconazole infusion appeared to be well tolerated in this population with a single adverse event (stinging at the site of infusion) deemed to be related to study drug administration. Based on the findings of this investigation, it appears that intravenous itraconazole can be administered to infants beyond 6 months, children, and adolescents using a weight-normalized approach to dosing.With both traditional and emerging fungal pathogens contributing to an increasing rate of morbidity, invasive mycoses remain a serious and potentially fatal complication for immunocompromised children (1,16,23,26,27,31). In recent years, a growing number of new therapeutic agents have found their way to market (28). However, the management of systemic fungal infections is still restricted to a relatively small number of drug classes encompassing a limited number of pharmacologic actions (i.e., most are cell wall-acting agents). As such, the spectrum of activity and established efficacy, in combination with the pharmacokinetic and toxicity profiles of each agent, will shape their role in therapy.Itraconazole is a first-generation synthetic triazole antifungal that has been in clinical use for nearly two decades. Although fungistatic against pathogenic yeast, itraconazole retains activity against a portion of fluconazole-resistant isolates and demonstrates fungicidal activity against a number of filamentous organisms that cause severe invasive disease (25). Compa...