Effect of rofecoxib on the pharmacokinetics of digoxin in healthy volunteers

Quantitatively Predicting Effects of Exercise on Pharmacokinetics of Drugs Using a Physiologically Based Pharmacokinetic Model

Exercise significantly alters human physiological functions, such as increasing cardiac output and muscle blood flow and decreasing glomerular filtration rate (GFR) and liver blood flow, thereby altering the absorption, distribution, metabolism, and excretion of drugs. In this study, we aimed to establish a database of human physiological parameters during exercise and to construct equations for the relationship between changes in each physiological parameter and exercise intensity, including cardiac output, organ blood flow (e.g., muscle blood flow and kidney blood flow), oxygen uptake, plasma pH and GFR, etc. The polynomial equation P = ΣaiHRi was used for illustrating the relationship between the physiological parameters (P) and heart rate (HR), which served as an index of exercise intensity. The pharmacokinetics of midazolam, quinidine, digoxin, and lidocaine during exercise were predicted by a whole-body physiologically based pharmacokinetic (WB-PBPK) model and the developed database of physiological parameters following administration to 100 virtual subjects. The WB-PBPK model simulation results showed that most of the observed plasma drug concentrations fell within the 5th-95th percentiles of the simulations, and the estimated peak concentrations (Cmax) and area under the curve (AUC) of drugs were also within 0.5-2.0 folds of observations. Sensitivity analysis showed that exercise intensity, exercise duration, medication time, and alterations in physiological parameters significantly affected drug pharmacokinetics and the net effect depending on drug characteristics and exercise conditions. In conclusion, the pharmacokinetics of drugs during exercise could be quantitatively predicted using the developed WB-PBPK model and database of physiological parameters. SIGNIFICANCE STATEMENT: This study simulated real-time changes of human physiological parameters during exercise in the WB-PBPK model and comprehensively investigated pharmacokinetic changes during exercise following oral and intravenous administration. Furthermore, the factors affecting pharmacokinetics during exercise were also revealed.

Strategy for the Prediction of Steady-State Exposure of Digoxin to Determine Drug-Drug Interaction Potential of Digoxin With Other Drugs in Digitalization Therapy

Digoxin, a narrow therapeutic index drug, is widely used in congestive heart failure. However, the digitalization therapy involves dose titration and can exhibit drug-drug interaction. Ctrough versus area under the plasma concentration versus time curve in a dosing interval of 24 hours (AUC0-24h) and Cmax versus AUC0-24h for digoxin were established by linear regression. The predictions of digoxin AUC0-24h values were performed using published Ctrough or Cmax with appropriate regression lines. The fold difference, defined as the quotient of the observed/predicted AUC0-24h values, was evaluated. The mean square error and root mean square error, correlation coefficient (r), and goodness of the fold prediction were used to evaluate the models. Both Ctrough versus AUC0-24h (r = 0.9215) and Cmax versus AUC0-24h models for digoxin (r = 0.7781) showed strong correlations. Approximately 93.8% of the predicted digoxin AUC0-24h values were within 0.76-fold to 1.25-fold difference for Ctrough model. In sharp contrast, the Cmax model showed larger variability with only 51.6% of AUC0-24h predictions within 0.76-1.25-fold difference. The r value for observed versus predicted AUC0-24h for Ctrough (r = 0.9551; n = 177; P < 0.001) was superior to the Cmax (r = 0.6134; n = 275; P < 0.001) model. The mean square error and root mean square error (%) for the Ctrough model were 11.95% and 16.2% as compared to 67.17% and 42.3% obtained for the Cmax model. Simple linear regression models for Ctrough/Cmax versus AUC0-24h were derived for digoxin. On the basis of statistical evaluation, Ctrough was superior to Cmax model for the prediction of digoxin AUC0-24h and can be potentially used in a prospective setting for predicting drug-drug interaction or lack of it.

Predictive Power of an In Vitro System to Assess Drug Interactions of an Antimuscarinic Medication: A Comparison of In Vitro and In Vivo Drug-Drug Interaction Studies of Trospium Chloride With Digoxin

The authors studied a potential drug-drug interaction via findings from in vitro and in vivo studies, to assess whether the in vitro system was predictive of in vivo clinical pharmacokinetic outcomes. An in vitro experiment and a clinical study were performed to assess the potential for interaction. The effect of trospium chloride on human P-glycoprotein-mediated transport of [3H]-digoxin was determined in vitro. A randomized, crossover clinical trial in 40 subjects was performed to evaluate the effect of trospium on the pharmacokinetics of digoxin in vivo. The findings from the studies were then compared. The in vitro findings in this study were corroborated by the clinical study via assessment of inhibition and impact on pharmacokinetic parameters. The in vitro system for assessment of a potential interaction of 2 drugs excreted primarily through the kidney was predictive of the pharmacokinetic outcomes obtained from a clinical setting.

Pharmacokinetics of digoxin in healthy subjects receiving taranabant, a novel cannabinoid-1 receptor inverse agonist

INTRODUCTION

Interaction studies with digoxin (Lanoxin; GlaxoSmithKline, Research Triangle Park, NC, USA), a commonly prescribed cardiac glycoside with a narrow therapeutic index and a long half-life, are typically required during the development of a new drug, particularly when it is likely that digoxin may be given to patients also treated with the new agent, taranabant--a cannabinoid-1 receptor inverse agonist--for weight loss. This study was designed to establish if this combination of therapy has the potential of a significant pharmacokinetic interaction.

METHODS

This open-label, fixed-sequence, two-period study investigated whether taranabant, administered to steady state, affects the well-described single-dose pharmacokinetics of digoxin. During the first period, 12 healthy men and women ranging in age from 21 to 35 years received a single oral dose of digoxin 0.5 mg. Following a 10-day wash out, they started a 19-day taranabant dosing regimen (6 mg once daily from day -14 to day 5) designed to establish and maintain steady-state levels of taranabant. On study day 1, subjects received a single oral dose of digoxin 0.5 mg. The plasma levels of digoxin were followed for an additional 4 days while the dosing of taranabant continued.

RESULTS

The geometric mean ratio and 90% confidence intervals for digoxin AUC(0-infinity) were 0.91 (0.83, 0.99), falling within the prespecified comparability intervals (CI) of (0.8, 1.25), which is within the usually allowed interval for bioequivalence. The geometric mean ratio and 90% CI for digoxin maximum plasma concentration (C(max)) were 1.23 (1.09, 1.40). The median time to C(max) was the same for both treatments.

CONCLUSION

Multiple doses of 6 mg taranabant do not have a clinically meaningful effect on the pharmacokinetics of a single oral dose of digoxin.

Evaluation of the pharmacokinetics of digoxin in healthy subjects receiving etoricoxib

AIMS

Digoxin is a commonly prescribed cardiac glycoside with a narrow therapeutic index. The aim was to investigate whether the cyclooxygenase-2 selective nonsteroidal anti-inflammatory drug etoricoxib affects the steady-state pharmacokinetics of digoxin.

METHODS

This was a double-blind, randomized, placebo-controlled, two-period cross-over study. In each period, 14 healthy volunteers ranging in age from 21 to 35 years received oral digoxin 0.25 mg daily and were randomized to either etoricoxib 120 mg or matching placebo tablets once daily for 10 days. Trough digoxin plasma concentrations were analysed by linear regression to examine digoxin accumulation over time.

RESULTS

The geometric mean ratios (etoricoxib/placebo) for AUC(0-24h), C(max) and urinary excretion were 1.06 (90% confidence interval 0.97, 1.17), 1.33 (1.21, 1.46) and 1.10 (1.00, 1.20), respectively. The median (range) for digoxin T(max) (h) values with etoricoxib and placebo were 0.5 (0.5, 1.5) and 1.0 (0.5, 1.5), respectively. Steady-state digoxin plasma concentrations were achieved by day 7 in each treatment period. No serious adverse experiences were reported.

CONCLUSIONS

Although etoricoxib 120 mg did produce an approximately 33% increase in digoxin C(max), this increase does not appear to be clinically meaningful, as cardiotoxicity with digoxin has been associated with elevations in steady-state rather than peak concentrations. From these results, it appears that etoricoxib does not cause any changes in digoxin steady-state pharmacokinetics that would necessitate a dose adjustment.

Pharmacokinetics of rofecoxib: a specific cyclo-oxygenase-2 inhibitor

Rofecoxib is a commonly used specific cyclo-oxygenase-2 (COX-2) inhibitor. Rofecoxib has high bioavailability, poor aqueous solubility, an elimination half-life suitable for daily administration and a volume of distribution approximating body mass. Species-specific, predominantly hepatic, metabolism occurs, with novel enterohepatic circulation in rats and O-glucuronidation by uridine diphosphate-glucuronosyl transferase (UGT) 2B7 and 2B15 in human liver microsomes. Discrepancies in studies of postoperative analgesia can be putatively explained by known pharmacokinetics. Changes in rofecoxib disposition and pharmacokinetics are evident between races, in elderly patients, in patients with chronic renal insufficiency and in patients with mild to moderate hepatic impairment. Despite the selective action of COX-2 inhibitors, there remains the potential for significant drug interactions. Rofecoxib has been shown to have interactions with rifampicin (rifampin), warfarin, lithium and angiotensin converting enzyme (ACE) inhibitors and theophylline. COX-2 inhibitors represent a major therapeutic advance in terms of gastrointestinal safety; however, long-term safety in other organ systems and with concomitant drug administration still remain to be proven.

Rofecoxib: an update on physicochemical, pharmaceutical, pharmacodynamic and pharmacokinetic aspects

Rofecoxib (MK-966) is a new generation non-steroidal anti-inflammatory agent (NSAID) that exhibits promising anti-inflammatory, analgesic and antipyretic activity. It selectively inhibits cyclooxygenase (COX)-2 isoenzyme in a dose-dependent manner in man. No significant inhibition of COX-1 is observed with rofecoxib up to doses of 1000 mg. The pharmacokinetics of rofecoxib has been found to be complex and variable. Mean oral bioavailability after single dose of rofecoxib (12.5, 25 or 50 mg) is 93% with t(max) varying widely between 2 and 9 h. It is highly plasma-protein bound and is metabolized primarily by cytosolic reductases to inactive metabolites. Rofecoxib is eliminated predominantly by hepatic metabolism with a terminal half-life of approximately 17 h during steady state. Various experimental models and clinical studies have demonstrated rofecoxib to be superior, or at least equivalent, in anti-inflammatory, analgesic and antipyretic efficacy to comparator nonselective NSAIDs in osteoarthritis, rheumatoid arthritis and other pain models. Emerging evidence suggests that rofecoxib may also find potential use as supportive therapy in various pathophysiologic conditions like Alzheimer's disease, and in various malignant tumours and polyps, where COX-2 is overly expressed. Rofecoxib is generally well-tolerated. Analysis of data pooled from several trials suggests that rofecoxib is associated with fewer incidences of clinically symptomatic gastrointestinal ulcers and ulcer complications vis-à-vis conventional NSAIDs. However, this gastropreserving effect may be negated by concurrent use of low-dose aspirin for cardiovascular risk reduction. Rofecoxib tends to show similar tolerability for renal and cardiothrombotic events as compared with nonnaproxen nonselective NSAIDs. No clinically significant drug interaction has been reported for rofecoxib except with diuretics, where it reverses their salt-wasting effect and thus can be clinically exploited in electrolyte-wasting disorders. There is only modest information about the physicochemical and pharmaceutical aspects of rofecoxib. Being poorly water soluble, its drug delivery has been improved using varied formulation approaches. Although it is stable in solid state, rofecoxib is photosensitive and base-sensitive in solution form with its degradation mechanistics elucidated. Analytical determinations of rofecoxib and its metabolites in biological fluids employing HPLC with varied types of detectors have been reported. Isolated studies have also been published on the chromatographic and spectrophotometric assay of rofecoxib and its degradants in bulk samples and pharmaceutical dosage forms. The current article provides an updated overview on the physicochemical, pharmaceutical, pharmacokinetic and pharmacodynamic vistas of rofecoxib.

[Clinical trials with rofecoxib: analysis of the information from the gender perspective]

BACKGROUND AND OBJECTIVE

There is evidence if the low rate of participation or even exclusion of women in clinical trials (CT), and that sex-differences are not considered in the design and analysis of the CT. The objectives of the study were to determine whether women are properly represented in the CT with rofecoxib and to analyze the information of CT with rofecoxib from a gender perspective.

MATERIAL AND METHOD

Twenty eight rofecoxib CT in adults have been reviewed, all indexed in Medline and published between 1999-2001. The FDA Guideline for the Study and Evaluation of Gender Differences in the Clinical Evaluation Drugs was used to analyze the information.

RESULTS

An 80% of the trials do not describe efficacy results by sex, and only one reports side effects by sex. A 78.3% does not report stratified analysis by sex. In the discussion the possible difference by sex of the results is mentioned in 3 occasions. Only 8% of the CT considers the influence of hormonal variation in the results. The pharmacokinetics issues related specifically to women are poorly followed: in 60% of the CT it is not specified the influence of oral contraceptives in the results of the trial, and in 88.9% of CT it is not specified the influence of estrogen treatment in the results of the trial. Pregnancy as exclusion criteria is only considered in 50% of the trials.

CONCLUSIONS

CT with rofecoxib has included more women than men. Important information on specific situation related to gender, recommends by FDA Guideline for the Study and Evaluation of Gender Differences in the Clinical Evaluation Drugs, have not been followed.

Rofecoxib: a review of its use in the management of osteoarthritis, acute pain and rheumatoid arthritis

Rofecoxib is a selective cyclo-oxygenase (COX)-2 inhibitor which has little or no effect on the COX-1 isoenzyme at doses up to 1000 mg/day. Rofecoxib has greater selectivity for COX-2 than celecoxib, meloxicam, diclofenac and indomethacin. In well-controlled clinical trials, rofecoxib 12.5 to 500 mg/day has been evaluated for its efficacy in the treatment of osteoarthritis, acute pain and rheumatoid arthritis [lower dosages (5 to 125 mg/day) were generally used in the chronic pain indications]. In the treatment of patients with osteoarthritis, rofecoxib was more effective in providing symptomatic relief than placebo, paracetamol (acetaminophen) and celecoxib and was similar in efficacy to ibuprofen, diclofenac, naproxen and nabumetone. Overall, both the physician's assessment of disease status and the patient's assessment of response to therapy tended to favour rofecoxib. In patients with postsurgical dental pain, pain after spinal fusion or orthopaedic surgery, or primary dysmenorrhoea, rofecoxib provided more rapid and more sustained pain relief and reduced requirements for supplemental morphine use after surgery than placebo. Rofecoxib was more efficacious than celecoxib in patients with acute dental pain and pain after spinal fusion surgery, although celecoxib may have been used at a subtherapeutic dose. In comparison with traditional nonsteroidal anti-inflammatory drugs (NSAIDs) ibuprofen, diclofenac and naproxen sodium, rofecoxib was similar in efficacy in the treatment of acute pain. Although naproxen sodium provided more rapid pain relief than rofecoxib in patients with primary dysmenorrhoea, the reverse was true after orthopaedic surgery: rofecoxib provided more rapid pain relief and less supplemental morphine was needed. Rofecoxib was as effective as naproxen in providing symptomatic relief for over 8700 patients with rheumatoid arthritis. Compared with traditional NSAID therapy, rofecoxib had a significantly lower incidence of endoscopically confirmed gastroduodenal ulceration and, in approximately 13,000 patients with osteoarthritis and rheumatoid arthritis, a lower incidence of gastrointestinal (GI) adverse events. Rofecoxib was generally well tolerated in all indications with an overall tolerability profile similar to traditional NSAIDs. The most common adverse events in rofecoxib recipients were nausea, dizziness and headache. In conclusion, rofecoxib is at least as effective as traditional NSAID therapy in providing pain relief for both chronic and acute pain conditions. Rofecoxib provides an alternative treatment option to traditional NSAID therapy in the management of symptomatic pain relief in patients with osteoarthritis. Initial data from patients with primary dysmenorrhoea and postoperative pain are promising and further trials may confirm its place in the treatment of these indications. Rofecoxib has also shown promising results in patients with rheumatoid arthritis and is likely to become a valuable addition to current drug therapy for this patient population. Importantly, rofecoxib is associated with a lower incidence of GI adverse events than traditional NSAIDs making it a primary treatment option in patients at risk of developing GI complications or patients with chronic conditions requiring long term treatment.