Lack of interaction between meloxicam and warfarin in healthy volunteers

Potential Underprediction of Warfarin Drug Interaction From Conventional Interaction Studies and Risk Mitigation: A Case Study With Epacadostat, an IDO1 Inhibitor

Drug-drug interaction (DDI) studies involving warfarin are typically conducted with subtherapeutic doses of warfarin to ensure the safety of volunteers. However, this approach may potentially have a systemic bias of underestimating pharmacodynamic (PD) DDI effect on warfarin at therapeutic levels of anticoagulation. We demonstrate here the utility of model-based DDI prediction for a clinically relevant warfarin regimen, using the example of epacadostat (INCB024360), the first-in-class indoleamine 2,3-dioxygenase 1 inhibitor in clinical development as a novel orally active immuno-oncological therapy. Observed data from a dedicated clinical DDI study using subtherapeutic warfarin suggested warfarin pharmacokinetics (PK), but not PD (anticoagulation), was significantly affected by concomitant epacadostat. However, subsequent PK/PD modeling and simulations indicated a clinically important DDI effect on warfarin PD at a higher baseline of the international normalization ratio (INR) and enabled recommendation of warfarin dose adjustment that is dependent on epacadostat dosing regimen and target INR.

[The problem of cardiac safety of nonsteroidal anti-inflammatory drugs]

The paper considers an update on the mechanisms for the development of adverse reactions of nonsteroidal anti-inflammatory drugs on the cardiovascular system.

Absence of an effect of T89 on the steady-state pharmacokinetics and pharmacodynamics of warfarin in healthy volunteers

This open-label, multi-dose, single-center, sequential, inpatient study evaluated the effects of a two herb combination drug (T89, Danshen plus Sanqi) on the steady-state pharmacodynamics (PD) and pharmacokinetics (PK) of warfarin in 24 healthy volunteers. Twenty-three subjects attained a stable international normalized ratio (INR) by taking warfarin alone prior to 1-week of added-on use of T89. INR was not increased after the addition of T89 for 7 days (P > .05). The 90% confidence interval (CI) of the geometric mean ratio for maximum plasma concentrations (Cmax) and area under curve (AUClast ) of both R- and S-warfarin when warfarin was administered with or without T89 was within the 0.80 to 1.25 equivalence ratio. These results indicate that T89 has no effect on the steady-state PD and PK of warfarin. Warfarin and T89 dose adjustments are not required when these two drugs are co-administrated in clinical practice.

Risk factors of drug interaction between warfarin and nonsteroidal anti-inflammatory drugs in practical setting

Nonsteroidal anti-inflammatory drugs (NSAIDs) are known to interact with the oral anticoagulant warfarin and can cause a serious bleeding complication. In this study, we evaluated the risk factors for international normalized ratio (INR) increase, which is a surrogate marker of bleeding, after addition of an NSAID in a total of 98 patients who used warfarin. Patient age, sex, body mass index, maintenance warfarin dose, baseline INR, coadministered medications, underlying diseases, and liver and kidney functions were evaluated for possible risk factors with INR increase > or =15.0% as the primary end-point. Of the 98 patients, 39 (39.8%) showed an INR elevation of > or =15.0% after adding a NSAID to warfarin therapy. Multivariate analysis showed that high maintenance dose (>40 mg/week) of warfarin (P=0.001), the presence of coadministered medications (P=0.024), the use of meloxicam (P=0.025) and low baseline INR value (P=0.03) were the risk factors for INR increase in respect to NSAID-warfarin interaction. In conclusion, special caution is required when an NSAID is administered to warfarin users if patients are taking warfarin >40 mg/week and other medications interacting with warfarin.

Effects of duloxetine on the pharmacodynamics and pharmacokinetics of warfarin at steady state in healthy subjects

This study evaluated the pharmacodynamics and pharmacokinetics of once-daily dosing of warfarin at steady state when taken concomitantly with once-daily doses of duloxetine. Healthy subjects with a stable international normalized ratio (INR) of 1.5 to 2.0 on an individualized fixed dose of warfarin (2-9 mg) in period 1 received daily warfarin and duloxetine (60 mg for 14 days [n = 15] or 60 mg for 4 days, then 120 mg for 10 days [n = 15]) in period 2. Across the 14-day period when warfarin was coadministered with duloxetine, the least squares mean INR changes from baseline (warfarin alone) ranged from -0.05 to +0.07, and the 90% confidence intervals ranged from -0.12 to +0.14. Following coadministration of warfarin with 60 mg duloxetine, but not with 120 mg duloxetine, there was a statistically significant prolongation in bleeding time compared to warfarin alone. For both R- and S-warfarin, the 90% confidence interval for the geometric mean ratios of area under the curve (AUC(tau,ss)) and maximum plasma concentrations (C(max,ss)) between warfarin administered alone and with 60 or 120 mg duloxetine were contained within the bioequivalence limits of 0.8 to 1.25. In conclusion, duloxetine had no clinically or statistically significant effect on the pharmacodynamics or pharmacokinetics of warfarin at steady state.

Meloxicam in rheumatoid arthritis

Rheumatoid arthritis (RA), a chronic inflammatory multisystem disorder marked by joint pain, stiffness, swelling and multiple systemic involvements, requires a multifaceted approach for its management. It includes symptomatic treatment with analgesics as well as disease-modifying medications to alter the course of RA over time. NSAIDS have been widely used for their symptomatic effects, but their use is not free from adverse effects, which may include life-threatening adverse events such as gastrointestinal (GI) bleeding and perforation. Meloxicam, an oxicam derivative that is a member of the enolic acid group of NSAIDs, has recently been approved by the US FDA for use in RA and osteoarthritis. At the FDA-recommended doses meloxicam is COX-2 preferential. By virtue of this COX-2 preferential activity it is expected to have lower GI toxicity as compared with COX-2 nonselective NSAIDs. Clinical trials have shown that meloxicam at 7.5 - 15 mg/day is as effective as diclofenac, piroxicam and naproxen as an anti-inflammatory and analgesic, and was associated with fewer GI adverse effects.

No effect of the novel antidiabetic agent nateglinide on the pharmacokinetics and anticoagulant properties of warfarin in healthy volunteers

The novel hypoglycemic agent nateglinide is pharmacologically distinct from oral hypoglycemic agents such as sulfonylureas and repaglinide. The present study investigated the effects in healthy volunteers of multiple doses of nateglinide on the pharmacokinetics and pharmacodynamics of warfarin. The study comprised a randomized two-group, two-way crossover, open-label design in 12 healthy male subjects. One group of 6 subjects initially received a single oral dose of warfarin 30 mg and then, after a 7- to 14-day washout, received both warfarin and nateglinide (120 mgnateglinide, 10 min before meals for 4 days and a single dose of 30 mg warfarin on the second day). The alternate group of 6 subjects received treatments in the opposite order. Pharmacokinetic profiles were derived from plasma warfarin and nateglinide concentrations. Prothrombin measurements were evaluated in both periods as a measure of warfarin activity. When administered alone or in combination, there were no statistically significant differences in mean warfarin (R- and S-enantiomers) or nateglinide pharmacokinetic parameters. The concurrent administration of nateglinide and warfarin did not affect the maximal change in prothrombin time that follows warfarin administration. In this study, there was no evidence of an effect of coadministration of nateglinide on the pharmacodynamic action of warfarin or any pharmacokinetic interaction between warfarin and nateglinide.

Effect of the catechol-O-methyltransferase inhibitor entacapone on the steady-state pharmacokinetics and pharmacodynamics of warfarin

AIMS

To investigate the influence of a multiple-dose regimen with the catechol-O-methyltransferase inhibitor entacapone on the pharmacokinetics and pharmacodynamics of warfarin.

METHODS

In a randomized, double-blind, two-way cross-over study, 12 healthy subjects (gender ratio 1 : 1) received treatment for 1 week with either entacapone 200 mg four times daily or placebo during individually optimized treatment with warfarin (INR 1.4-1.8). The effect of entacapone on the steady-state pharmacokinetics of both R- and S-warfarin was determined and, in addition, INR values were measured. The key pharmacokinetic variables were AUCss, Cmax and tmax.

RESULTS

Entacapone increased the exposure to R-warfarin by 18% (90% CI: 111, 126%), and caused a 13% (6, 19%) increase in INR values. No effect was seen on the pharmacokinetics of the pharmacologically more potent S-enantiomer. Safety and tolerability variables did not show any difference between the treatment phases.

CONCLUSIONS

In healthy subjects, entacapone displays a slight pharmacokinetic interaction with R-warfarin but, based on the lack of a clinically relevant pharmacodynamic interaction, it appears that it can also be used safely in Parkinson's disease patients who are receiving warfarin.

Meloxicam

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Assessment of the quality and quantity of drug-drug interaction studies in recent NDA submissions: study design and data analysis issues

This report investigates the quality and quantity of drug-drug interaction studies in recent new drug applications (NDAs). Eighty-nine studies contained in 14 NDAs submitted between December 1995 and November 1996 to the U.S. Food and Drug Administration (FDA) were reviewed. The results indicated that the median number of clinical drug-drug interaction studies per NDA was 6, almost double that of a 1994-1995 survey. In vitro metabolism data were present in 70% of the submissions. More than 50% of the submissions contained interaction studies using a battery of drugs (cimetidine, digoxin, or warfarin) without optimal use of the in vitro metabolism or in vivo mass balance data. Various study designs using a median number of 12 subjects were employed in the evaluation of drug-drug interactions. Some of the important study design factors such as dose size, dosing regimen, dosing duration, and timing of coadministration were considered, although not consistently, by the sponsors in their study design. Seventy-five percent of the studies used normal, healthy male subjects, and 25% used patients for whom the new molecular entities were intended. In 33% of the studies, female subjects were also recruited. Although the majority (80%) of the submissions still used p-values to determine the significance of drug interactions, 30% used a more relevant equivalence approach with 90% confidence intervals for key pharmacokinetic and/or pharmacodynamic parameter ratios to assess the extent of drug interactions. Overall, 82% of the studies concluded no interaction. Although population pharmacokinetic analysis can be a useful tool in studying drug-drug interactions, only 21% of the submissions used this approach. In summary, this assessment reveals that the quantity and quality of drug-drug interaction studies in NDAs have improved over the years. These improvements, as well as others that can be implemented, should result in more informative labeling and better patient care. FDA guidance for industry dealing with the design, analysis, and labeling language of in vivo metabolic drug-drug interactions has been developed to assist sponsors and FDA reviewers with these issues.

The cyclooxygenase-2 inhibitors: safety and effectiveness

OBJECTIVE

To review the development of cyclooxygenase-2 (COX-2) inhibitors and discuss specific agents that are currently under investigation or have been marketed.

DATA SOURCES

Primary literature on selective COX inhibitors was identified from a comprehensive MEDLINE, English-literature search from January 1966 through September 1998, with additional studies selected by review of the references. Abstracts from recent meetings and package insert literature from approved agents were also used as source material. Indexing terms included COX-2 inhibitors, meloxicam, celecoxib, rofecoxib, flosulide, SC-58635, and MK-966.

STUDY SELECTION

Human clinical, pharmacokinetic, and dose-ranging trials performed in Europe and the US and randomized comparative trials were reviewed.

DATA SYNTHESIS

With the discovery of at least two COX isoforms, a better understanding of the mechanism of action and gastrointestinal toxicity of nonsteroidal antiinflammatory drugs (NSAIDs) has been realized. While COX-1 is involved in physiologic maintenance, COX-2 seems to be involved in inflammation, mitogenesis, and specialized signal transductions. Selective COX-2 inhibitors may allow maximum antiinflammatory activity while improving the safety profile associated with NSAID therapy. Celecoxib and rofecoxib have been approved by the Food and Drug Administration for the treatment of osteo- and rheumatoid arthritis; meloxicam is undergoing Phase III clinical trials. Preliminary data indicate that the selective COX-2 inhibitors provide analgesic and antiinflammatory efficacy comparable with older NSAIDs, with fewer adverse gastrointestinal effects.

CONCLUSIONS

Specific COX-2 inhibitors offer promising benefits over older NSAIDs with regard to gastrointestinal safety while maintaining analgesic and antiinflammatory efficacy. Further study is required to determine long-term efficacy and safety in clinical use.