Influence of age and cytochrome P450 2C9 genotype on the steady-state disposition of diclofenac and celecoxib

Effects of fluconazole on the pharmacokinetics of celecoxib and its carboxylic acid metabolite in different CYP2C9 genotypes

This study aimed to investigate the effects of fluconazole, a moderate inhibitor of CYP2C9 and CYP3A4, on the pharmacokinetics of celecoxib and its carboxylic acid metabolite in different CYP2C9 genotypes. A total of thirty-nine healthy Korean male volunteers were divided into three different CYP2C9 genotype groups (CYP2C9*1/*1, *1/*3 and *3/*3 genotypes) and were enrolled in the celecoxib alone trial, celecoxib with fluconazole trial, or both. In the celecoxib alone trial, participants received a single oral dose of 200 mg celecoxib. In the celecoxib with fluconazole trial, participants received 300 mg fluconazole on day 1, 150 mg fluconazole once daily for four consecutive days (day 2-5), and a coadministration of 200 mg celecoxib with 150 mg fluconazole on day 6. Plasma concentrations of celecoxib and celecoxib carboxylic acid were determined by using HPLC-MS/MS. In the CYP2C9*1/*1 genotype group, fluconazole treatment increased AUCinf of celecoxib by 2.61-fold, and decreased CL/F by 60.4% (both p < 0.001). In the CYP2C9*1/*3 genotype group, fluconazole treatment increased AUCinf of celecoxib by 2.44-fold (p < 0.001), prolonged t1/2 by 1.36-fold (p < 0.05), and decreased CL/F by 60.4% (p < 0.001). Fluconazole treatment increased AUCinf of celecoxib by 2.23-fold, prolonged t1/2 by 1.64-fold, and decreased CL/F by 53.8% in the subject with CYP2C9*3/*3 genotype. Cmax of celecoxib carboxylic acid significantly decreased in CYP2C9*1/*1 and *1/*3 genotypes (p < 0.01 and p < 0.05, respectively), following fluconazole treatment, whereas AUCinf showed no significant changes in any CYP2C9 genotype group. In conclusion, fluconazole affected the pharmacokinetics of celecoxib in different CYP2C9 genotypes.

Pharmacogenetics and Pain Treatment with a Focus on Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) and Antidepressants: A Systematic Review

Background: This systematic review summarizes the impact of pharmacogenetics on the effect and safety of non-steroidal anti-inflammatory drugs (NSAIDs) and antidepressants when used for pain treatment. Methods: A systematic literature search was performed according to the preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines regarding the human in vivo efficacy and safety of NSAIDs and antidepressants in pain treatment that take pharmacogenetic parameters into consideration. Studies were collected from PubMed, Scopus, and Web of Science up to the cutoff date 18 October 2021. Results: Twenty-five articles out of the 6547 initially detected publications were identified. Relevant medication–gene interactions were noted for drug safety. Interactions important for pain management were detected for (1) ibuprofen/CYP2C9; (2) celecoxib/CYP2C9; (3) piroxicam/CYP2C8, CYP2C9; (4) diclofenac/CYP2C9, UGT2B7, CYP2C8, ABCC2; (5) meloxicam/CYP2C9; (6) aspirin/CYP2C9, SLCO1B1, and CHST2; (7) amitriptyline/CYP2D6 and CYP2C19; (8) imipramine/CYP2C19; (9) nortriptyline/CYP2C19, CYP2D6, ABCB1; and (10) escitalopram/HTR2C, CYP2C19, and CYP1A2. Conclusions: Overall, a lack of well powered human in vivo studies assessing the pharmacogenetics in pain patients treated with NSAIDs or antidepressants is noted. Studies indicate a higher risk for partly severe side effects for the CYP2C9 poor metabolizers and NSAIDs. Further in vivo studies are needed to consolidate the relevant polymorphisms in NSAID safety as well as in the efficacy of NSAIDs and antidepressants in pain management.

Physiologically based pharmacokinetic (PBPK) modeling for prediction of celecoxib pharmacokinetics according to CYP2C9 genetic polymorphism

Celecoxib is a non-steroidal anti-inflammatory drug (NSAID) and a representative selective cyclooxygenase (COX)-2 inhibitor, which is commonly prescribed for osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, acute pain, and primary dysmenorrhea. It is mainly metabolized by CYP2C9 and partly by CYP3A4 after oral administration. Many studies reported that CYP2C9 genetic polymorphism has significant effects on the pharmacokinetics of celecoxib and the occurrence of adverse drug reactions. The aim of this study was to develop a physiologically based pharmacokinetic (PBPK) model of celecoxib according to CYP2C9 genetic polymorphism for personalized pharmacotherapy. Initially, a clinical pharmacokinetic study was conducted where a single dose (200 mg) of celecoxib was administered to 39 healthy Korean subjects with CYP2C9*1/*1 or CYP2C9*1/*3 genotypes to obtain data for PBPK development. Based on the conducted pharmacokinetic study and a previous pharmacokinetic study involving subjects with CYP2C9*1/*13 and CYP2C9*3/*3 genotype, PBPK model for celecoxib was developed. A PBPK model for CYP2C9*1/*1 genotype group was developed and then scaled to other genotype groups (CYP2C9*1/*3, CYP2C9*1/*13 and CYP2C9*3/*3). After model development, model validation was performed with comparison of five pharmacokinetic studies. As a result, the developed PBPK model of celecoxib successfully described the pharmacokinetics of each CYP2C9 genotype group and its predicted values were within the acceptance criterion. Additionally, all the predicted values were within two-fold error range in comparison to the previous pharmacokinetic studies. This study demonstrates the possibility of determining the appropriate dosage of celecoxib for each individual through the PBPK modeling with CYP2C9 genomic information. This approach could contribute to the reduction of adverse drug reactions of celecoxib and enable precision medicine.

Celecoxib is a substrate of CYP2D6: Impact on celecoxib metabolism in individuals with CYP2C9*3 variants

Celecoxib was characterized as a substrate of human cytochrome P450 (CYP) 2D6 in vitro. In recombinant CYP2D6, celecoxib hydroxylation showed atypical substrate inhibition kinetics with apparent K_m, K_i, and V_max of 67.2 μM, 12.6 μM, and 1.33 μM/min, respectively. In human liver microsomes (HLMs), a concentration-dependent inhibition of celecoxib hydroxylation by quinidine was observed after CYP2C9 and CYP3A4 were inhibited. In individual HLMs with variable CYP2D6 activities, a significant correlation was observed between celecoxib hydroxylation and CYP2D6-selective dextromethorphan O-demethylation when CYP2C9 and CYP3A4 activities were suppressed (r = 0.97, P < 0.0001). Molecular modeling showed two predominant docking modes of celecoxib with CYP2D6, resulting in either a substrate or an inhibitor. A second allosteric binding antechamber, which stabilized the inhibition mode, was revealed. Modeling results were consistent with the observed substrate inhibition kinetics. Using HLMs from individual donors, the relative contribution of CYP2D6 to celecoxib metabolism was found to be highly variable and dependent on CYP2C9 genotypes, ranging from no contribution in extensive metabolizers with CYP2C9*1*1 genotype to approximately 30% in slow metabolizers with allelic variants CYP2C9*1*3 and CYP2C9*3*3. These results demonstrate that celecoxib may become a potential victim of CYP2D6-associated drug-drug interactions, particularly in individuals with reduced CYP2C9 activity.

Genomic Variation and Pharmacokinetics in Old Age: A Quantitative Review of Age- vs. Genotype-Related Differences

Older persons may particularly benefit from pharmacogenetic diagnostics, but there is little clinical evidence on that question. We quantitatively analyzed the effects of age and genotype in drugs with consensus on a therapeutically relevant impact of a genotype. Assuming additive effects of age and genotype, drugs may be classified in groups with different priorities to consider either age, or genotype, or both, in therapy. Particularly interesting were those studies specifically analyzing the age‐by‐genotype interaction.

Analysis of the variability of the pharmacokinetics of multiple drugs in young adult and elderly subjects and its implications for acceptable daily exposures and cleaning validation limits

The elderly constitute a significant, potentially sensitive, subpopulation within the general population, which must be taken into account when performing risk assessments including determining an acceptable daily exposure (ADE) for the purpose of a cleaning validation. Known differences in the pharmacokinetics of drugs between young adults (who are typically the subjects recruited into clinical trials) and the elderly are potential contributors affecting the interindividual uncertainty factor (UF_H) component of the ADE calculation. The UF_H values were calculated for 206 drugs for young adult and elderly groups separately and combined (with the elderly assumed to be a sensitive subpopulation) from published studies where the pharmacokinetics of the young adult and elderly groups were directly compared. Based on the analysis presented here, it is recommended to use a default UF_H value of 10 for worker populations (which are assumed to be approximately equivalent to the young adult groups) where no supporting pharmacokinetic data exist, while it is recommended to use a default UF_H value of 15 for the general population, to take the elderly into consideration when calculating ADE values. The underlying reasons for the large differences between the exposures in the young adult and elderly subjects for the 10 compounds which show the greatest separation are different in almost every case, involving the OCT2 transporter, glucuronidation, hydrolysis, CYP1A2, CYP2A6, CYP2C19, CYP2D6, CYP3A4 or CYP3A5. Therefore, there is no consistent underlying mechanism which appears responsible for the largest differences in pharmacokinetic parameters between young adult and elderly subjects.

A stratified randomized double-blind phase II trial of celecoxib for treating patients with cervical intraepithelial neoplasia: The potential predictive value of VEGF serum levels: An NRG Oncology/Gynecologic Oncology Group study

PURPOSE

To examine the effect of celecoxib on cervical intraepithelial neoplasia 3 (CIN 3). This is a NRG Oncology/Gynecologic Oncology Group study with translational biomarkers.

PATIENTS AND METHODS

Patients with CIN 3 were randomized to celecoxib 400mg once daily (67 patients) or placebo (63 patients) for 14-18weeks. The primary outcome measure was histologic regression. A test of equal probabilities of success between two therapies was conducted, using Fisher's Exact Test at alpha=10% and 90% power when the treatment arm boosted the probability of success by 30%. Translational analysis included cervical tissue HPV genotyping, COX-2 expression in biopsies, and serum celecoxib and VEGF levels.

RESULTS

In primary analysis, histologic regression was not significantly higher in the celecoxib group (40%) than in the placebo group (34.1%). However, exploratory analyses suggest patients with high serum VEGF levels exhibited greater regression in the celecoxib arm (47.3%) than in the placebo arm (14.3%). Regression rates were similar by treatment group in patients with low VEGF. VEGF levels increased over time in the placebo group, but remained the same in the treatment group. COX-2 expression in cervical biopsies declined from pre-treatment to the end of treatment with celecoxib; it did not change with placebo.

CONCLUSIONS

Celecoxib at 400mg once daily for 14-18weeks did not significantly decrease the severity of CIN 3 compared with placebo except, possibly, in subjects with high baseline VEGF. Therefore, serum VEGF levels might identify patients who may benefit from celecoxib or other therapies, personalizing future chemoprevention trials for CIN 3.

Effects of CYP2C9 genetic polymorphisms on the pharmacokinetics of celecoxib and its carboxylic acid metabolite

Celecoxib, a selective cyclooxygenase (COX)-2 inhibitor, is used for the treatment of rheumatoid arthritis and osteoarthritis. The predominant hepatic metabolism of celecoxib to celecoxib carboxylic acid (CCA) is mediated mainly by CYP2C9. We investigated the effects of the major CYP2C9 genetic variants in Asian populations, CYP2C9*3 and CYP2C9*13, on the pharmacokinetics of celecoxib and its carboxylic acid metabolite in healthy Korean subjects. A single 200-mg oral dose of celecoxib was given to 52 Korean subjects with different CYP2C9 genotypes: CYP2C9EM (n = 26; CYP2C9*1/*1), CYP2C9IM (n = 24; CYP2C9*1/*3 and *1/*13), and CYP2C9PM (n = 2; CYP2C9*3/*3). Celecoxib and CCA concentrations in plasma samples collected up to 48 or 96 h after drug intake were determined by HPLC-MS/MS. The mean area under the plasma concentration-time curve (AUC_0-∞) of celecoxib was increased 1.63-fold (P < 0.001), and the apparent oral clearance (CL/F) of celecoxib was decreased by 39.6% in the CYP2C9IM genotype group compared with that of CYP2C9EM (P < 0.001). The overall pharmacokinetic parameters for celecoxib in CYP2C9*1/*13 subjects were similar to those in CYP2C9*1/*3 subjects. Two subjects with CYP2C9PM genotype both showed markedly higher AUC_0-∞, prolonged half-life, and lower CL/F for celecoxib than did subjects with CYP2C9EM and IM genotypes. CYP2C9*3 and CYP2C9*13 variant alleles significantly affected the plasma concentration of celecoxib.

Effect of body weight on fixed dose of diclofenac for the prevention of post-endoscopic retrograde cholangiopancreatography pancreatitis

OBJECTIVE

The aim of this study was to assess the influence of patient body weight on the clinical effect of 100 mg diclofenac administered as a single dose for the prevention of post-endoscopic retrograde cholangiopancreatography pancreatitis (PEP).

MATERIALS AND METHODS

All patients subjected to endoscopic retrograde cholangiopancreatography (ERCP) from 2009 to 2014 were evaluated for inclusion. In total, 772 patients were included of whom 378 (49%) received diclofenac prophylaxis.

RESULTS

In the diclofenac prophylaxis group, body weight was higher in patients with PEP (mean ± SD: 82 ± 18 kg) than in patients without PEP (74 ± 18 kg) (p = 0.029). In patients not receiving prophylaxis, body weight was not associated with the occurrence of PEP (mean ± SD: 77 ± 18 vs 75 ± 18 kg, respectively, p = 0.450). In an adjusted analysis, higher patient body weight was inversely associated with the clinical effect of 100 mg diclofenac for the prophylaxis of PEP.

CONCLUSIONS

High patient body weight was associated with a reduced effect of 100 mg diclofenac for prophylaxis of PEP.

Genetic Polymorphisms of Cytochrome P450 Enzymes and the Effect on Interindividual, Pharmacokinetic Variability in Extensive Metabolizers

Genetic polymorphisms of cytochrome P450 (CYP) enzymes are one of the factors that contribute to the pharmacokinetic (PK) variability of drugs. PK variability is observed in the bimodal distribution between extensive metabolizers (EMs) and poor metabolizers (PMs). PK variability may also exist between individuals genotyped as homozygous EMs and heterozygous EMs. This may carry implications for drug dosing and drug response (e.g., risk of therapeutic failure or drug toxicity). Studies have reported significant PK differences between homozygous and heterozygous EMs. Some literature suggests that this distinction may be of clinical relevance. Due to study design limitations and data that are either sparse or conflicting, generalizations regarding the potential impact of the CYP genotype, within EMs, are difficult. Optimally designed clinical trials are needed. This review evaluates the potential impact of CYP genetic polymorphisms on interindividual PK variability of drugs within an EM population.

Pharmacogenomics of acetylsalicylic acid and other nonsteroidal anti-inflammatory agents: clinical implications

PURPOSE

Pharmacogenomics investigates interindividual genetic variability in the DNA sequence of drug targets, drug-metabolizing enzymes or disease genes, RNA expression, or protein translation of genes affecting drug response and drug safety. Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most commonly prescribed medications with well-documented variation in patient response in terms of efficacy and safety. This variation may in part be explained by pharmacogenomics.

METHODS

In this paper I review data on the pharmacogenomics of aspirin and other NSAIDs focusing on clinical implications.

RESULTS

Existing scientific evidence supports the pharmacogenomic basis of interindividual variation in treatment response to aspirin and NSAIDs, with clinical implications for antiplatelet action, cancer chemoprevention, and drug safety. However, further research efforts are needed before knowledge on the pharmacogenomics of aspirin and NSAIDs can be implemented in clinical practice.

CONCLUSION

The outcome of these research efforts would be anticipated to have added value for both science and society, contributing to the enhanced efficacy and safety of these agents through patient selection.

Pharmacogenetics of nonsteroidal anti-inflammatory drugs

With the beginning of the Human Genome Project, an emerging field of science was brought to the forefront of the pharmaceutical community. Pharmacogenetics facilitates optimization of the current patient-centered care model and pharmacotherapy as a whole. Utilizing these ever-expanding branches of science to nonsteroidal anti-inflammatory drugs (NSAIDs) can provide novel opportunities to affect patient care. With a wide range of NSAID choices available as treatment options for relieving pain and/or reducing inflammation or fever, a more systematic way of selecting the ideal agent for the patients based upon their genetic information could spare them from a potentially permanent health-care condition. Furthermore, if a patient possesses or lacks certain alleles, serious adverse events can be anticipated and avoided. The tailoring of drug therapy can be achieved using the published data and cutting-edge genetic testing to attain a higher standard of care for patients.

Antiretroviral therapy adherence and drug-drug interactions in the aging HIV population

It is estimated that by 2015 more than half of all HIV-infected individuals in the United States will be 50 years of age or older. As this population ages, the frequency of non-AIDS related comorbidities increases, which includes cardiovascular, metabolic, gastrointestinal, genitourinary and psychiatric disorders. As a result, medical management of the aging HIV population can be complicated by polypharmacy and higher pill burden, leading to poorer antiretroviral therapy (ART) adherence. Adherence to ART is generally better in older populations when compared to younger populations; however, cognitive impairment in elderly patients can impair adherence, leading to worse treatment outcomes. Practical monitoring tools can improve adherence and increase rates of viral load suppression. Several antiretroviral drugs exhibit inhibitory and/or inducing effects on cytochrome P450 isoenzymes, which are responsible for the metabolism of many medications used for the treatment of comorbidities in the aging HIV population. The combination of ART with polypharmacy significantly increases the chance of potentially serious drug-drug interactions (DDIs), which can lead to drug toxicity, poorer ART adherence, loss of efficacy of the coadministered medication, or virologic breakthrough. Increasing clinicians awareness of common DDIs and the use of DDI programs can prevent coadministration of potentially harmful combinations in elderly HIV-infected individuals. Well designed ART adherence interventions and DDI studies are needed in the elderly HIV population.

Drug metabolism in older people--a key consideration in achieving optimal outcomes with medicines

Hepatic clearance plays a key role in determining the systemic exposure of drugs and metabolites, which in turn has a major effect on variability in the beneficial and adverse effects of medicines. Aging results in a number of significant changes in the human liver including reductions in liver blood flow, size, drug-metabolizing enzyme content, and pseudocapillarization. Drug metabolism is also influenced by comorbid disease, frailty, concomitant medicines, and (epi)genetics. These changes have the potential to alter the hepatic clearance of drugs but need to be interpreted in the context of the pharmacokinetic (and pharmacodynamic) characteristics of the drug of interest. There is growing evidence that the age-related changes in the liver not only result in a decrease in the hepatic clearance of unbound drug but also influence variability in response to medicines in older people.

Polymorphism of human cytochrome P450 enzymes and its clinical impact

Pharmacogenetics is the study of how interindividual variations in the DNA sequence of specific genes affect drug response. This article highlights current pharmacogenetic knowledge on important human drug-metabolizing cytochrome P450s (CYPs) to understand the large interindividual variability in drug clearance and responses in clinical practice. The human CYP superfamily contains 57 functional genes and 58 pseudogenes, with members of the 1, 2, and 3 families playing an important role in the metabolism of therapeutic drugs, other xenobiotics, and some endogenous compounds. Polymorphisms in the CYP family may have had the most impact on the fate of therapeutic drugs. CYP2D6, 2C19, and 2C9 polymorphisms account for the most frequent variations in phase I metabolism of drugs, since almost 80% of drugs in use today are metabolized by these enzymes. Approximately 5-14% of Caucasians, 0-5% Africans, and 0-1% of Asians lack CYP2D6 activity, and these individuals are known as poor metabolizers. CYP2C9 is another clinically significant enzyme that demonstrates multiple genetic variants with a potentially functional impact on the efficacy and adverse effects of drugs that are mainly eliminated by this enzyme. Studies into the CYP2C9 polymorphism have highlighted the importance of the CYP2C9*2 and *3 alleles. Extensive polymorphism also occurs in other CYP genes, such as CYP1A1, 2A6, 2A13, 2C8, 3A4, and 3A5. Since several of these CYPs (e.g., CYP1A1 and 1A2) play a role in the bioactivation of many procarcinogens, polymorphisms of these enzymes may contribute to the variable susceptibility to carcinogenesis. The distribution of the common variant alleles of CYP genes varies among different ethnic populations. Pharmacogenetics has the potential to achieve optimal quality use of medicines, and to improve the efficacy and safety of both prospective and currently available drugs. Further studies are warranted to explore the gene-dose, gene-concentration, and gene-response relationships for these important drug-metabolizing CYPs.

Pharmacokinetics and drug metabolism in the elderly

Aging involves progressive impairments in the functional reserve of multiple organs, which might also affect drug metabolism and pharmacokinetics. In addition, the elderly population will develop multiple diseases and, consequently, often has to take several drugs. As the hepatic first-pass effect of highly cleared drugs could be reduced (due to decreases in liver mass and perfusion), the bioavailability of some drugs can be increased in the elderly. Significant changes in body composition occur with advancing age. Lipophilic drugs may have an increased volume of distribution (Vd) with a prolonged half-life, and water-soluble drugs tend to have a smaller Vd. In the elderly, hepatic drug clearance of some drugs can be reduced by up to 30% and CYP-mediated phase I reactions are more likely to be impaired than phase II metabolism, which is relatively preserved in the elderly. Concerning the most important CYP3A4 studies with human liver microsomes and clinical studies with the validated probe, midazolam, it is indicated that there are no significant differences in CYP3A4 activity between young and old populations. Finally, renal excretion is decreased (up to 50%) in about two thirds of elderly subjects, but confounding factors such as hypertension and coronary heart disease account also for a decline in kidney function. In conclusion, age-related physiological and pharmacokinetic changes as well as the presence of comorbidity and polypharmacy will complicate drug therapy in the elderly.

Polymorphisms of human cytochrome P450 2C9 and the functional relevance

Human cytochrome P450 2C9 (CYP2C9) accounts for ∼20% of hepatic total CYP content and metabolizes ~15% clinical drugs such as phenytoin, S-warfarin, tolbutamide, losartan, and many nonsteroidal anti-inflammatory agents (NSAIDs). CYP2C9 is highly polymorphic, with at least 33 variants of CYP2C9 (*1B through *34) being identified so far. CYP2C9*2 is frequent among Caucasians with ~1% of the population being homozygous carriers and 22% are heterozygous. The corresponding figures for the CYP2C9*3 allele are 0.4% and 15%, respectively. There are a number of clinical studies addressing the impact of CYP2C9 polymorphisms on the clearance and/or therapeutic response of therapeutic drugs. These studies have highlighted the importance of the CYP2C9*2 and *3 alleles as a determining factor for drug clearance and drug response. The CYP2C9 polymorphisms are relevant for the efficacy and adverse effects of numerous NSAIDs, sulfonylurea antidiabetic drugs and, most critically, oral anticoagulants belonging to the class of vitamin K epoxide reductase inhibitors. Warfarin has served as a practical example of how pharmacogenetics can be utilized to achieve maximum efficacy and minimum toxicity. For many of these drugs, a clear gene-dose and gene-effect relationship has been observed in patients. In this regard, CYP2C9 alleles can be considered as a useful biomarker in monitoring drug response and adverse effects. Genetic testing of CYP2C9 is expected to play a role in predicting drug clearance and conducting individualized pharmacotherapy. However, prospective clinical studies with large samples are warranted to establish gene-dose and gene-effect relationships for CYP2C9 and its substrate drugs.

Genetically based impairment in CYP2C8- and CYP2C9-dependent NSAID metabolism as a risk factor for gastrointestinal bleeding: is a combination of pharmacogenomics and metabolomics required to improve personalized medicine?

Polymorphisms in CYP2C8 and CYP2C9 are common in all the human populations and many CYP2C8 and CYP2C9 gene variations cause decreased enzyme activity towards the NSAIDs aceclofenac, celecoxib, diclofenac, ibuprofen, indomethazine, lornoxicam, meloxicam, naproxen, piroxicam, tenoxicam and valdecoxib. This impairment in drug biodisposition alters drug pharmacokinetics, with carriers of detrimental mutations displaying increased values of AUC and decreased drug clearance. Individuals carrying the gene variants CYP2C8*3 (rs11572080; rs10509681), CYP2C9*2 (rs1799853) or CYP2C9*3 (rs1057910) show increased risk of developing acute gastrointestinal bleeding during the use of NSAID that are CYP2C8 or CYP2C9 substrates. However, it is not known whether parent drugs or products of alternative metabolic pathways are responsible for bleeding. We present an overview of the current knowledge of relevant polymorphisms of CYP2C8 and CYP2C9 genes, their association with NSAID metabolism and pharmacokinetics and a meta-analysis that confirms the clinical significance of these gene variations with regard to gastrointestinal bleeding.

Enantioselective Pharmacokinetics of Ibuprofen and Involved Mechanisms

Although dexibuprofen (S-ibuprofen) was marketed in Austria and Switzerland, the racemate at various formulations is still extensively used worldwide, and there are no indications that the racemate will be replaced by the single enantiomer. Thus, elucidation of the characteristics and involved mechanisms of the chiral pharmacokinetics of racemic ibuprofen is of special importance for the understanding of the pharmacological and toxicological consequences, and for prediction of the clinically potential drug interactions and influence of the pathological states. Stereoselective pharmacokinetics and metabolism are common features for chiral nonsteroidal antiinflammatory drugs (NSAIDs) and especially for 2-arylpropionic acid derivatives characterized with a chiral center adjacent to the carboxyl group. Although the enantioselective pharmacokinetic characteristics of different NSAIDs should be treated case by case, they share similar mechanisms underlying the protein binding, metabolism and chiral inversion. Ibuprofen was the most extensively researched drug in terms of chiral characteristics and mechanisms. Therefore, elucidation of the mechanisms derived from research on ibuprofen may provide better understanding and prediction of other chiral drugs. This article attempts to elucidate the chiral pharmacokinetics and involved mechanisms of ibuprofen in comparison with other NSAIDs based on recent developments. Topics on history of ibuprofen, enantioselective analysis method, absorption, protein binding, conventional metabolism, metabolic chiral inversion, gene polymorphism, and biochemical developments were included. It is worth mentioning that some underlying biochemical mechanisms, especially for the metabolic chiral inversion and ethnic differences still remain to be seen. Further research is required to develop human-resourced researching model and to provide more evidence concerning the site of inversion, species variation, CYP450 gene polymorphisms, and biochemical mechanisms.

Pharmacogenetics of analgesics: toward the individualization of prescription

The use of analgesics is based on the empiric administration of a given drug with clinical monitoring for efficacy and toxicity. However, individual responses to drugs are influenced by a combination of pharmacokinetic and pharmacodynamic factors that can sometimes be regulated by genetic factors. Whereas polymorphic drug-metabolizing enzymes and drug transporters may affect the pharmacokinetics of drugs, polymorphic drug targets and disease-related pathways may influence the pharmacodynamic action of drugs. After a usual dose, variations in drug toxicity and inefficacy can be observed depending on the polymorphism, the analgesic considered and the presence or absence of active metabolites. For opioids, the most studied being morphine, mutations in the ABCB1 gene, coding for P-glycoprotein (P-gp), and in the µ-opioid receptor reduce morphine potency. Cytochrome P450 (CYP) 2D6 mutations influence the analgesic effect of codeine and tramadol, and polymorphism of CYP2C9 is potentially linked to an increase in nonsteroidal anti-inflammatory drug-induced adverse events. Furthermore, drug interactions can mimic genetic deficiency and contribute to the variability in response to analgesics. This review summarizes the available data on the pharmacokinetic and pharmacodynamic consequences of known polymorphisms of drug-metabolizing enzymes, drug transporters, drug targets and other nonopioid biological systems on central and peripheral analgesics.

Celecoxib concentration predicts decrease in prostaglandin E2 concentrations in nipple aspirate fluid from high risk women

Background

Epidemiologic studies suggest that long term low dose celecoxib use significantly lowers breast cancer risk. We previously demonstrated that 400 mg celecoxib taken twice daily for 2 weeks lowered circulating plasma and breast nipple aspirate fluid (NAF) prostaglandin (PG)E₂ concentrations in post- but not premenopausal high risk women. We hypothesized that circulating concentrations of celecoxib influenced PGE₂ response, and that plasma levels of the drug are influenced by menopausal status. To address these hypotheses, the aims of the study were to determine: 1) if circulating plasma concentrations of celecoxib correlated with the change in plasma or NAF PGE₂ concentrations from baseline to end of treatment, and 2) whether menopausal status influenced circulating levels of celecoxib.

Methods

Matched NAF and plasma were collected from 46 high risk women who were administered celecoxib twice daily for two weeks, 20 subjects receiving 200 mg and 26 subjects 400 mg of the agent. NAF and plasma samples were collected before and 2 weeks after taking celecoxib.

Results

In women taking 400 mg bid celecoxib, plasma concentrations of the agent correlated inversely with the change in NAF PGE₂ levels from pre- to posttreatment. Nonsignificant trends toward higher celecoxib levels were observed in post- compared to premenopausal women. There was a significant decrease in NAF but not plasma PGE₂ concentrations in postmenopausal women who took 400 mg celecoxib (p = 0.03).

Conclusion

In high risk women taking 400 mg celecoxib twice daily, plasma concentrations of celecoxib correlated with downregulation of PGE₂ production by breast tissue. Strategies synergistic with celecoxib to downregulate PGE₂ are of interest, in order to minimize the celecoxib dose required to have an effect.

Clinical use and pharmacological properties of selective COX-2 inhibitors

Selective COX-2 inhibitors (coxibs) are approved for the relief of acute pain and symptoms of chronic inflammatory conditions such as osteoarthritis (OA) and rheumatoid arthritis (RA). They have similar pharmacological properties but a slightly improved gastrointestinal (GI) safety profile if compared to traditional nonsteroidal anti-inflammatory drugs (tNSAIDs). However, long-term use of coxibs can be associated with an increased risk for cardiovascular (CV) adverse events (AEs). For this reason, two coxibs were withdrawn from the market. Currently celecoxib, etoricoxib, and lumiracoxib are used. These three coxibs differ in their chemical structure and selectivity for COX-2, which might explain some of their pharmacological features. Following oral administration, the less lipophilic celecoxib has a lower bioavailability (20-40%) than the other two coxibs (74-100%). All are eliminated by hepatic metabolism involving mainly CYP2C9 (celecoxib, lumiracoxib) and CYP3A4 (etoricoxib). Elimination half-life varies from 5 to 8 h (lumiracoxib), 11 to 16 h (celecoxib) and 19 to 32 h (etoricoxib). In patients with liver disease, plasma levels of celecoxib and etoricoxib are increased about two-fold. Clinical efficacies of the coxibs are comparable to tNSAIDs. There is an ongoing discussion about whether the slightly better GI tolerability (which is lost if acetylsalicylic acid is coadministered) of the coxibs is offset by their elevated risks for CV AEs (also seen with tNSAIDs other than naproxen), which apparently increase with dose and duration of exposure. In addition, the higher costs for coxibs (if compared to tNSAIDs, even when a "gastroprotective" proton pump inhibitor is coadministered) should be taken into consideration, if a coxib will be selected for certain patients with a high risk for GI complications. For such treatment, the lowest effective dose should be used for a limited time. Monitoring of kidney function and blood pressure appears advisable. It is hoped that further controlled studies can better define the therapeutic place of the coxibs.

Pharmacokinetic-Pharmacodynamic Crisis in the Elderly

Advances in medical technology have led to improved survival after catastrophic illnesses. Many of the survivors require ongoing care including tracheostomy, mechanical ventilation, tube feedings, and indwelling venous catheters. Repeated hospitalizations may be necessary to treat infectious complications resulting from resistant organisms requiring intravenous antibiotic therapy. Because prolonged intravenous access may be difficult or even impossible in these patients, alternative means of therapy are necessary. Linezolid is the first of a new class of antimicrobial agents known as the oxazolidinones with activity against gram-positive bacteria similar to that of vancomycin and yet its oral bioavailability allows for enteral administration. We present our retrospective experience with oral linezolid in a cohort of pediatric intensive care unit patients. Primary infectious disease issues included endocarditis, tracheitis, pneumonia, or central line sepsis resulting from Staphylococcus epidermidis, methicillin-resistant Staphylococcus aureus, and Enterococcus. Treatment was initiated with vancomycin and changed to enteral linezolid (10 mg/kg every 12 hours). The duration of therapy with linezolid varied from 7 days to 6 weeks. All of the patients were discharged home to complete their course of enteral linezolid. No complications related to linezolid therapy were noted, and all of the patients completed their prescribed course of therapy without the need for rehospitalization. Our preliminary experience suggests that oral linezolid offers an effective alternative to intravenous vancomycin for the treatment of infections resulting from gram-positive bacteria and avoids the need for prolonged vascular access.

Clinical pharmacology of celecoxib, a COX-2 selective inhibitor

NSAIDs are extensively used worldwide; nonetheless, they are associated with adverse gastrointestinal (GI) effects. COX-2 inhibitors (coxibs) have been developed to reduce pain and inflammation without associated GI and bleeding risks. Celecoxib was the first COX-2 inhibitor introduced on the market, and it still remains so, whereas rofecoxib and valdecoxib were withdrawn due to excess cardiovascular (CV) risk. There is consequently a concern that CV toxicity reflects a class effect of all COX-2 inhibitors. Celecoxib possesses anti-inflammatory and analgesic properties, and the evidence for CV risk is rather small and comparable to that of other traditional NSAIDs in short-term treatments (of < 4 weeks). It could be suggested that the use of low doses of celecoxib (100 mg b.i.d.) in short-treatment, especially in patients with previous experience of GI events and the recommendation of avoiding use of celecoxib in patients with CV history or risk, contribute in the decision-making process of prescribing COX-2 or NSAIDs.

[Clinical pharmacogenomics for CYP2C8 and CYP2C9: general concepts and application to the use of NSAIDs]

OBJECTIVE

To study the major mutations in genes CYP2C8 and CYP2C9, their frequency in populations of diverse ethnical descent, their analysis methods, and the major drugs with affected metabolism, with a special emphasis on NSAIDs.

METHOD

Repeated searches of Pubmed (January 1966-January 2006) and Scholar Google were performed. All searches were restricted to studies in humans, and papers not written in Spanish or English were excluded.

RESULTS

Ten allelic variants of CYP2C8 and 24 of CYP2C have been reported. Not all of them exert a relevant effect on drug metabolism. In Caucasians 22% of CYP2C8 genes and 31% of CYP2C9 genes have mutations. In Asians fewer than 1% and nearly 3% are mutated, respectively. Major identification methods include endonuclease digestion, PCR, pyrosequencing, and microarrays. Not all NSAIDs are exclusive substrates for CYP2C8/9. The usefulness of allelic variant analysis varies with each individual drug. The risk for digestive hemorrhage associated with the CYP2C9 genotype is particularly relevant when using aceclofenac, celecoxib, diclofenac, ibuprofen, indomethacin, lornoxicam, piroxicam, or naproxen.

CONCLUSIONS

Although CYP2C8/9 activity plays an essential role in the metabolism of and clinical response to many NSAIDs, the use of pharmacogenomic techniques is not equally useful for all these drugs.

Clinical implications of pharmacogenetics of cytochrome P450 drug metabolizing enzymes

For many drugs, pharmacogenetic polymorphisms are known affecting biotransformation and clinical outcome. The clinical importance of these variants depends on allele-frequency and the effect size of the clinical outcome parameters. Further, it depends on the therapeutic range of the drug which is affected, on predictability of drug response as well as on duration until onset of therapeutic efficacy. Consequences which arise from genotyping might be: adjustment of dose according to genotype, choice of therapeutic strategy or even choice of drug. In antidepressant drug treatment, most drugs are metabolized via the polymorphic cytochrome P450 enzyme CYP2D6. Huge differences in pharmacokinetic parameters have been consistently shown for many tricyclics, some SSRIs, and other antidepressant drugs whereas the effects on therapeutic efficacy and adverse events have been described controversially. In cardiovascular disease, oral anticoagulants, nonsteroidal anti-inflammatory drugs, oral hypoglycemic drugs and other drugs are affected by genetic polymorphisms of the cytochrome P450 drug metabolizing enzyme CYP2C9. Studies in patients or healthy volunteers revealed up to 10-fold differences in pharmacokinetic parameters due to genetic polymorphisms of CYP2C9. Pharmacogenetics based dose adjustments are one tool to individualize drug treatment according to genetic factors. They can be derived from pharmacokinetic data with the aim to obtain equal drug concentrations in each individual. Prospective validation of dose adjustments based on pharmacogenetics should be performed before routine application of such strategies. A controlled prospective clinical trial with one arm receiving genotype-based dose adjustments and the other arm receiving therapy as usual will elucidate the benefit of pharmacogenomics-based individualization of certain drug therapies.

Linking pharmacovigilance with pharmacogenetics

The ability to identify individuals who are susceptible to adverse drug reactions (ADRs) has the potential to reduce the personal and population costs of drug-related morbidity. Some individuals may show an increased susceptibility to certain ADRs through genetic polymorphisms that alter their responses to various drugs. We wished to establish a methodology that would be acceptable to members of the general population and that would enable estimation of the risks that specific genetic factors confer on susceptibility to specific ADRs. Buccal swabs were selected as a minimally invasive method to obtain cells for DNA extraction. We wished to determine whether DNA of sufficient quantity and quality could be obtained to enable genotyping for two different polymorphic genes that code for enzymes that are widely involved in drug disposition. This article describes a small pilot study of methodology developed in the New Zealand Intensive Medicines Monitoring Programme (IMMP) to link prescription event monitoring (PEM) studies with pharmacogenetics. The methodology involves a nested case-control study design to investigate whether patients with genetic variants in P-glycoprotein (P-gp) and cytochrome P450 (CYP) 2C9 are more susceptible to psychiatric or visual disturbances following cyclo- oxygenase-2 inhibitor use (ADR signals identified in the IMMP database) than matched control patients taking the medication without experiencing any ADRs. It was concluded that the use of buccal swabs is acceptable to patients and provides DNA of sufficient quantity and quality for genotyping. Although no differences in the distribution of genotypes in the case and control populations were found in this small study, case-control studies investigating genetic risks for ADRs using drug cohorts from PEM studies are possible, and there are several areas where population-based studies of genetic risk factors for ADRs are needed. Examples are discussed where research in large populations is required urgently. These are: (i) genetic variations affecting P-gp function; (ii) variations affecting drugs metabolised by CYP2C9 and other polymorphic CYP enzymes; (iii) genetic variation in beta-adrenergic receptors and adverse outcomes from beta-adrenoceptor agonist therapy; and (iv) genetic variation in cardiac cell membrane potassium channels and their association with long QT syndromes and serious cardiac dysrhythmias. Such studies will help to identify factors that increase the risk of unwanted outcomes from drug therapy. They will also help to establish in what circumstances genotyping should be performed prior to commencing drug treatment and in tailoring drug treatment for individual patients.

Discordance between availability of pharmacogenetics studies and pharmacogenetics-based prescribing information for the top 200 drugs

BACKGROUND

Despite growing numbers of pharmacogenetics studies, little pharmacogenetics-based prescribing information is available to practitioners. It is possible that the lack of prescribing data for commonly used drugs is due to a paucity of evidence-based pharmacogenetics literature for these agents.

OBJECTIVE

To investigate the relationship between pharmacogenetics prescribing data in drug package inserts (PIs) and pharmacogenetics research literature for agents represented in the top 200 prescribed drugs for 2003.

METHODS

A PubMed search (to August 7, 2004) was performed to identify pharmacogenetics studies relevant to the top 200 drugs. These data were compared with PIs for drugs in the top 200 list that contained pharmacogenetics prescribing information.

RESULTS

Pharmacogenetics data in the literature were available for 71.3% of the top 200 drugs. The gene involved coded for a drug-metabolizing enzyme in 34.5% of the literature sampled. The remaining 65.5% of the pharmacogenetics studies contained information largely related to genetic variability in target proteins and drug transporters. Three drugs with PIs containing pharmacogenetics prescribing information deemed to be useful to guide therapy were in the top 200 list (celecoxib, fluoxetine, pantoprazole). There was no consensus on the strength of association between genetic variability and drug response for these agents.

CONCLUSIONS

The lack of specific pharmacogenetics-based prescribing information in PIs for commonly used drugs does not seem to be related to a paucity of pharmacogenetics data in the research literature. Rather, other factors including, but not limited to, the uncertain clinical relevance of genetic associations may make practical prescribing recommendations difficult.

Impact of CYP2C9 genotype on pharmacokinetics: are all cyclooxygenase inhibitors the same?

The market withdrawals of rofecoxib (Vioxx) and valdecoxib (Bextra) have focused considerable attention on the side effect profiles of cyclooxygenase (COX) inhibitors. As a result, attempts will be made to identify risk factors in the hope that physicians might be able to ensure patient safety. At first glance, CYP2C9 genotype might be considered a risk factor because many COX inhibitors are CYP2C9 substrates in vitro. This observation has led some to hypothesize that a reduction in clearance, in subjects expressing variant forms of the enzyme (e.g., CYP2C9*1/*3 or CYP2C9*3/*3 genotype), will lead to increased exposure and a greater risk of cardiovascular or gastrointestinal side effects. For any drug, however, one has to consider all clearance pathways. Therefore, a number of COX inhibitors were surveyed and it was determined that CYP2C9 plays a relatively minor role in the overall clearance ( Collapse

Key Words Collapse

MESH Headings

• Animals
• Aryl Hydrocarbon Hydroxylases/genetics
• Aryl Hydrocarbon Hydroxylases/metabolism
• Cardiovascular System/drug effects
• Cyclooxygenase 2 Inhibitors/pharmacokinetics
• Cyclooxygenase Inhibitors/pharmacokinetics
• Cytochrome P-450 CYP2C8
• Cytochrome P-450 CYP2C9
• Cytochrome P-450 CYP3A
• Cytochrome P-450 Enzyme System/genetics
• Cytochrome P-450 Enzyme System/metabolism
• Gastrointestinal Tract/drug effects
• Genotype
• Humans
• Polymorphism, Genetic
• Risk Factors
• Substrate Specificity

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Grants Collapse

Affiliation(s)

A David Rodrigues Drug Metabolosm, Bristol-Myers Squibb, Princeton, NJ 08543, USA.

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Polymorphisme génétique et interactions médicamenteuses : leur importance dans le traitement de la douleur

OBJECTIVES

To evaluate the impact of certain genetic polymorphisms on variable responses to analgesics

SOURCES

Systematic review, by means of a structured computerized search in the Medline database (1966-2004). Articles in English and French were selected. References in relevant articles were also retrieved.

MAIN FINDINGS

Most analgesics are metabolized by CYP isoenzymes subject to genetic polymorphism. NSAIDs are metabolized by CYP2C9; opioids described as "weak" (codeine, tramadol), anti-depressants and dextromethorphan are metabolized by CYP2D6 and some "potent" opioids (buprenorphine, methadone or fentanyl) by CYP3A4/5. After the usual doses have been administered, drug toxicity or, on the contrary, therapeutic ineffectiveness may occur, depending on polymorphism and the substance. Drug interactions mimicking genetic defects because of the existence of CYP inhibitors and inducers, also contribute to the variable response to analgesics. Some opioids are substrates of P-gp, a transmembrane transporter also subject to genetic polymorphism. However, P-gp could only play a minor modulating role in man on the central effects of morphine, methadone and fentanyl.

CONCLUSION

In the near future, pharmacogenetics should enable us to optimize therapeutics by individualizing our approach to analgesic drugs and making numerous analgesics safer and more effective. The clinical usefulness of these individualized approaches will have to be demonstrated by appropriate pharmacoeconomic studies and analyses.

[Does genomics determine efficacy of analgesics?]

Recent advances in knowledge about gene structure derived from the human genome project has also revealed data on genomic variation and their possible impact on complex and acute diseases as well as pharmacotherapy. The hypothesis of a genetic predisposition for complex diseases such as pain syndromes, side effects, and adverse outcomes challenging the clinician is ready to be tested by advanced genetic-epidemiologic study designs employing the latest genotyping technology. In pain therapy, the genetic background of the efficacy of analgesics, especially of opioids, is of particular interest. Genetic differences in drug kinetics and dynamics, e.g., differences in metabolism or genetic variations of the drug target (e.g., receptors) will be of importance in the future. Pharmacogenetics can individualize pharmacotherapy and improve care by predicting the optimal dose and avoiding side effects and toxicity in individual patients.

Relative impact of covariates in prescribing warfarin according to CYP2C9 genotype

Patients on warfarin anticoagulant therapy demonstrate wide variation in maintenance dose. Patients possessing variants (*2 and *3) of the cytochrome P450 2C9 gene require reduced maintenance doses compared to those having wild-type alleles (*1). Many other clinical factors have been shown to affect warfarin dose as well. To determine the relative impact of CYP2C9 genotype, age, gender, body surface area, concomitant medication, treatment indication and comorbidity, we conducted a retrospective cohort study in 453 patients managed by the anticoagulation service of a large, horizontally integrated, multispecialty group practice. In this largely Caucasian patient population, the CYP2C9 gene frequencies for *1/*1, *1/*2, *1/*3, *2/*2, *2/*3 and *3/*3 were 65.1%, 19.0%, 12.1%, 1.6%, 1.8% and 0.4%, respectively, approximating Hardy-Weinberg equilibrium. Mean maintenance doses for these genotypes were 36.5, 29.1, 23.5, 28.0, 18.1 and 5.5 mg/week, respectively. In univariate analyses, genotype alone accounted for 19.8% of the variability in maintenance dose. Age, body surface area and male gender accounted for 14.6%, 7.5% and 4.7%, respectively, while cardiac valve replacement as the indication for warfarin accounted for 5.4% of the variability. Collectively, these factors accounted for 33.7% of all dosing variability according to multiple regression. These results will help strengthen the mathematical models that are currently being developed for prospective gene-based warfarin dosing.

The CYP2C9 polymorphism: from enzyme kinetics to clinical dose recommendations

CYP2C9 is the major human enzyme of the cytochrome P450 2C subfamily and metabolizes approximately 10% of all therapeutically relevant drugs. Two inherited SNPs termed CYP2C9*2 (Arg144Cys) and *3 (Ile359Leu) are known to affect catalytic function. Numerous rare or functionally silent polymorphisms have been identified. About 35% of the Caucasian population carries at least one *2 or *3 allele. CYP2C9 metabolizes several oral hypoglycemics, oral anticoagulants, non-steroidal anti-inflammatory drugs and other drugs, including phenytoin, losartan, fluvastatin, and torsemide. In vitro studies with several drugs indicate that the Cys144 (.2) and Leu359 (.3) variants confer only about 70 and 10% of the intrinsic clearance of the wild-type protein (.1), respectively. The clinical pharmacokinetic implications of these polymorphisms vary depending on the enzymes contribution to total oral clearance. Several studies demonstrated that the CYP2C9 polymorphisms are medically important for non-steroidal anti-inflammatory drugs, for oral hypoglycemics, vitamin K antagonistic oral anticoagulants, and phenytoin. In particular, CYP2C9 polymorphisms should be routinely considered in therapy with oral anticoagulants where severe adverse events at initiation of therapy might be reduced by genotyping. CYP2C9 polymorphisms were also clinically associated with side effects of phenytoin, with gastric bleeding during therapy with non-steroidals and with hypoglycemia under oral hypoglycemic drugs. Data appear mature enough for the routine consideration of CYP2C9 genotypes in therapy with acenocoumarol, phenytoin, warfarin, and some other drugs. Nevertheless, it is advisable before the routine clinical use of these genotype data to rigorously test the benefits of genotype-based therapeutic recommendations by randomized controlled clinical trials.

Drug interactions in dentistry

BACKGROUND

The hepatic and intestinal cytochrome, or CY, P450 enzyme system is responsible for the biotransformation of a multitude of drugs. Certain medications used in dentistry can act as substrates, inducers or inhibitors of this system.

METHODS

The authors conducted a MEDLINE search of articles appearing between 1976 and the present using the keywords "drug interactions" and "cytochrome P450," and reviewed reports involving dental therapeutic agents using PubMed links from an Indiana University CYP450 drug interaction table on the World Wide Web.

RESULTS

The antibiotics erythromycin and clarithromycin are potent inhibitors of CYP3A4 and can increase blood levels and toxicity of CYP3A4 substrates. Likewise, quinolone antibiotics such as ciprofloxacin inhibit the metabolism of CYP1A2 substrates. Other dental therapeutic agents are substrates for CYP2C9 (celecoxib, ibuprofen and naproxen), CYP2D6 (codeine and tramadol), CYP3A4 (methylprednisolone) and CYP2E1 (acetaminophen). Because codeine and tramadol are prodrugs, inhibition of their metabolism can lead to a diminution of their analgesic effects. While inducers of acetaminophen metabolism, including alcohol, theoretically can increase the proportion of it that is biotransformed into a potentially hepatotoxic metabolite, recent research suggests that concomitant alcohol intake does not increase the hepatotoxic potential of therapeutic doses of acetaminophen.

CONCLUSIONS

A number of clinically significant drug interactions can arise with dental therapeutic agents that act as substrates or inhibitors of the CYP450 system. Clinical Implications. As polypharmacy continues to increase, the likelihood of adverse drug interactions in dentistry will increase as well. Ensuring that patients' medical histories are up to date and acquiring knowledge of the various substrates, inducers and inhibitors of the CYP450 system will help practitioners avoid potentially serious adverse drug interactions.