Potential drug-drug interactions when managing status epilepticus patients in intensive care: A cohort study.

AIMS: The risk for drug-drug interactions (DDIs) associated with antiseizure drugs (ASDs) used to manage status epilepticus (SE) patients in the intensive care unit (ICU) has been poorly investigated. We aimed to quantify and describe those potential DDIs and determine SE patient risk profiles. METHODS: We conducted an observational bi-centric cohort study including all SE patients admitted to the ICU in the period 2016-2020. RESULTS: Overall, 431 SE patients were included and 5504 potential DDIs were identified including 1772 DDIs (33%) between ASDs, 2610 DDIs (47%) between ASDs and previous usual treatments (PUTs), and 1067 DDIs (20%) between ASDs and ICU treatments (ICUTs). DDIs were moderate (n = 4871), major (n = 562) or severe (n = 16). All patients exhibited potential DDIs, which were major-to-severe DDIs in 47% of the cases. DDIs were pharmacokinetic (n = 1972, 36%), mostly involving cytochrome P450 modulators, and pharmacodynamic (n = 3477, 64%), mainly leading to increased sedation. ASD/PUT DDIs were the most frequent and severe. Age, PUT and ASD drug numbers and length of ICU stay were significantly associated with increased DDI number. We identified four SE patient profiles with different DDI risks and outcomes including (1) epileptic or brain trauma patients, (2) withdrawal syndrome patients, (3) older patients with comorbidities and (4) self-poisoned patients with psychiatric disorders and/or past epilepsy. CONCLUSION: SE patients are subject to potential DDIs between ASDs, ASD/PUT and ASD/ICUT. Major-to-severe DDIs mostly occur between ASDs and PUTs. Physicians should pay attention to SE patient characteristics and history to limit DDI numbers and prevent their consequences.

Changes in Alcohol Use after Metabolic and Bariatric Surgery: Predictors and Mechanisms.

PURPOSE OF REVIEW: This review synthesized the literature on predictors and mechanisms of post-bariatric alcohol problems, in order to guide future research on prevention and treatment targets. RECENT FINDINGS: Consistent evidence suggests an elevated risk of developing problems with alcohol following bariatric surgery. While there is a paucity of empirical data on predictors of problematic alcohol use after bariatric surgery, being male, a younger age, smoking, regular alcohol consumption, pre-surgical alcohol use disorder, and a lower sense of belonging have predicted alcohol misuse post-operatively. This review synthesizes potential mechanisms including specific bariatric surgical procedures, peptides and reinforcement/reward pathways, pharmacokinetics, and genetic influences. Finally, potential misperceptions regarding mechanisms are explored. Certain bariatric procedures elevate the risk of alcohol misuse post-operatively. Future research should serve to elucidate the complexities of reward signaling, genetically mediated mechanisms, and pharmacokinetics in relation to alcohol use across gender and developmental period by surgery type.

Effect of body weight and composition on efavirenz, atazanavir or darunavir concentration.

BACKGROUND: To compare the steady state plasma concentrations (Css) of three antiretroviral drugs in both normal and overweight patients, and to determine the relationship between Css and fat mass (FM) or lean body mass. METHODS: Patients treated for more than 6 months once daily with one of the antiretroviral drugs: efavirenz (EFV) 600mg, atazanavir boosted with ritonavir (ATV-r) 300mg/100mg, or darunavir boosted with ritonavir (DRV-r) 800mg/100mg, combined with two nucleoside analogues, were enrolled prospectively. One at steady state, plasma samples for the assessment of drug concentration were taken and body composition was assessed by bioelectrical impedance. RESULTS: One hundred and thirty-nine patients were enrolled (46, 45 and 48 in the groups EFV, ATV-r and DRV-r respectively). Their mean age was 46.2±10.4 years, 58% were male, 55.4% were from Sub Sahara African (SSA); body mass index (BMI) was 25.4±4.4kg/m2. Mean drug plasma Css of the three drugs did not differ according to BMI group. DRV-r Css tended to be higher in patients with BMI≥25kg/m2 (2896.7±1689 versus 2091.9±1038, P=0.09) and was significantly correlated with FM (r=0.3, P=0.02). In subgroup analysis, the effect of FM on DRV-r Css was significant in patients from SSA (r=0.4, P=0.04). CONCLUSIONS: Css result from many factors and body composition has been shown to only weakly influence interindividual variability but should be investigated in morbidly obese patients treated with DRV-r.

[Opioids prescription in the vulnerable populations : the children and the elderly. Practical guidelines]. / Prescription des opioïdes chez les patients vulnérables : les enfants et les personnes âgées. Recommandations pratiques.

Pain management in ambulatory care regularly requires the prescription of opioids. These drugs allow adequate analgesia achievement in many patients, but inefficiency and/or intolerable side effects may limit their use. Factors related to physiological particularities, comorbidities and comedication, as well as difficulties related to drug intake and pain assessment, make children and the elderly more vulnerable to variability in opioid response and problems of safety and efficacy profile. The purpose of this article is to remain the specificities of these two populations and to propose recommendations for the good use of opioids for ambulatory care.

La prise en charge de la douleur en médecine de ville nécessite régulièrement le recours à la prescription d'opioïdes. Une antalgie adéquate est obtenue chez de nombreux patients, mais une inefficacité et/ou des effets indésirables intolérables peuvent limiter leur utilisation. Les facteurs liés aux particularités physiologiques, aux comorbidités et aux comédications, les difficultés liées à la prise médicamenteuse et l'évaluation de la douleur, rendent l'enfant et le sujet âgé plus vulnérables à la variabilité de réponse aux opioïdes et aux problèmes de sécurité et d'efficacité. Le présent article a pour but de rappeler les spécificités de ces deux populations aux extrêmes de l'âge et de proposer des recommandations de bon usage des opioïdes pour la médecine ambulatoire.

Is the clinical relevance of drug-food and drug-herb interactions limited to grapefruit juice and Saint-John's Wort?

An interaction of drug with food, herbs, and dietary supplements is usually the consequence of a physical, chemical or physiologic relationship between a drug and a product consumed as food, nutritional supplement or over-the-counter medicinal plant. The current educational review aims at reminding to the prescribing physicians that the most clinically relevant drug-food interactions may not be strictly limited to those with grapefruit juice and with the Saint John's Wort herbal extract and may be responsible for changes in drug plasma concentrations, which in turn decrease efficacy or led to sometimes life-threatening toxicity. Common situations handled in clinical practice such as aging, concomitant medications, transplant recipients, patients with cancer, malnutrition, HIV infection and those receiving enteral or parenteral feeding may be at increased risk of drug-food or drug-herb interactions. Medications with narrow therapeutic index or potential life-threatening toxicity, e.g., the non-steroidal anti-inflammatory drugs, opioid analgesics, cardiovascular medications, warfarin, anticancer drugs and immunosuppressants may be at risk of significant drug-food interactions to occur. Despite the fact that considerable effort has been achieved to increase patient' and doctor's information and ability to anticipate their occurrence and consequences in clinical practice, a thorough and detailed health history and dietary recall are essential for identifying potential problems in order to optimize patient prescriptions and drug dosing on an individual basis as well as to increase the treatment risk/benefit ratio.

Screening for genotypic and phenotypic variations in CYP450 activity in patients with therapeutic problems in a psychiatric setting, a retrospective study.

OBJECTIVES: This retrospective study aimed to assess to what extent an adverse drug reaction (ADR), an abnormal therapeutic drug monitoring (TDM) or a non-response, was attributable to an abnormal cytochrome P450 activity in a psychiatric setting. METHOD: We collected the results of investigations performed in these situations related to psychotropic drugs between January 2005 and November 2014. Activities of different cytochrome P450 were assessed by genotyping and/or phenotyping. Two experienced clinical pharmacologists assessed independently the possible association between the event and the results of the investigations. RESULTS: One hundred and thirty eight clinical or biological situations had a complete assessment of all major metabolic pathways of the target drug. A majority of clinical or biological situations were observed with antidepressants (n=93, 67.4%), followed by antipsychotics (n=28, 20.3%), benzodiazepines and hypnotics (n=13, 9.4%), and psychostimulants (n=4, 2.9%). Genotype and/or phenotype determination was mainly performed because of ADRs (n=68, 49.3%) or non-response (n=46, 33.3%). Inter-rate reliability of the scoring system between the pharmacologists was excellent (kappa=0.94). The probability of an association between ADR, TDM or non-response and metabolic status was rated as intermediate to high in 34.7% of all cases, with proportions of 30.4% and 36.7%, for non-response and ADR respectively. CONCLUSION: When indicated by clinical pharmacologists, ADR, TDM or non-response may be attributable to a variation of the metabolic status with an intermediate to high probability in 34.7% of patients, based on the congruent assessment made by two clinical pharmacologists. Further studies assessing the clinical relevance of prospective explorations and clarifying the appropriate method according to the clinical context are needed.

The effect of morbid obesity on morphine glucuronidation.

The purpose of the present work was to study the change in morphine metabolic ratio in obese subjects before and after Roux-en-Y Gastric Bypass (RYGB) and to identify clinical and/or biological factors associated with this change. The pharmacokinetics (PK) of oral morphine (30mg), morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) was performed in patients before (n=25; mean BMI=43.2 (35.4-61.9)kg/m2), 7-15days (n=16) and 6 months after RYGB (n=19; mean BMI=32.3 (25.4-46.0)kg/m2). Morphine Cmax and AUC0-inf were significantly increased and morphine Tmax significantly shortened at 6 months after RYGB compared with preoperative data, indicating an important increase in the rate and extent of morphine absorption. The morphine metabolic ratio 0-inf M3G+M6G/Morphine, decreased significantly from the preoperative to 6 months postoperative period with an average of -26% (range -74%; +21%; p=0.004), but not in the immediate post-operative period. The change in morphine metabolic ratio was associated with a change in BMI, fat mass in kg, and triglyceride levels (rho=0.5, p≤0.04). The degree of change in several markers of low-grade inflammation, or the level of liver steatosis and fibrosis before surgery, was not associated with the change in morphine metabolic ratios. Our findings indicate that RYGB-induced weight loss significantly decreases morphine metabolic ratio, arguing for an effect of morbid obesity on glucuronidation. With glucuronide exposure at 6 months similar to preoperative values, a higher morphine AUC0-inf should encourage reducing morphine dosage in patients undergoing RYGB and chronically receiving immediate-release oral morphine.

Oral Morphine Pharmacokinetic in Obesity: The Role of P-Glycoprotein, MRP2, MRP3, UGT2B7, and CYP3A4 Jejunal Contents and Obesity-Associated Biomarkers.

The objective of our work was to study the association between the jejunal expression levels of P-gp, MRP2, MRP3, UGT2B7, CYP3A4, the ABCB1 c.3435C > T polymorphism, and several obesity-associated biomarkers, as well as oral morphine and glucuronides pharmacokinetics in a population of morbidly obese subjects. The pharmacokinetics of oral morphine (30 mg) and its glucuronides was performed in obese patients candidate to bariatric surgery. A fragment of jejunal mucosa was preserved during surgery. Subjects were genotyped for the ABCB1 single nucleotide polymorphism (SNP) c.3435C > T. The subjects were 6 males and 23 females, with a mean body mass index of 44.8 (35.4-61.9) kg/m(2). The metabolic ratios AUC0-inf M3G/morphine and AUC0-inf M6G/morphine were highly correlated (rs = 0.8, p < 0.0001) and were 73.2 ± 24.6 (34.7-137.7) and 10.9 ± 4.1 (3.8-20.6). The pharmacokinetic parameters of morphine and its glucuronides were not associated with the jejunal contents of P-gp, CYP3A4, MRP2, and MRP3. The jejunal content of UGT2B7 was positively associated with morphine AUC0-inf (rs = 0.4, p = 0.03). Adiponectin was inversely correlated with morphine Cmax (rs = -0.44, p = 0.03). None of the factors studied was associated with morphine metabolic ratios. The interindividual variability in the jejunal content of drug transporters and metabolizing enzymes, the ABCB1 gene polymorphism, and the low-grade inflammation did not explain the variability in morphine and glucuronide exposure. High morphine metabolic ratio argued for an increased morphine glucuronidation in morbidly obese patients.

Quantitative Atlas of Cytochrome P450, UDP-Glucuronosyltransferase, and Transporter Proteins in Jejunum of Morbidly Obese Subjects.

Protein expression levels of drug-metabolizing enzymes and transporters in human jejunal tissues excised from morbidly obese subjects during gastric bypass surgery were evaluated using quantitative targeted absolute proteomics. Protein expression levels of 15 cytochrome P450 (CYP) enzymes, 10 UDP-glucuronosyltransferase (UGT) enzymes, and NADPH-P450 reductase (P450R) in microsomal fractions from 28 subjects and 49 transporters in plasma membrane fractions from 24 of the same subjects were determined using liquid chromatography-tandem mass spectrometry. Based on average values, UGT1A1, UGT2B15, UGT2B17, SGLT1, and GLUT2 exhibited high expression levels (over 10 fmol/µg protein), though UGT2B15 expression was detected at a high level in only one subject. CYP2C9, CYP2D6, CYP3A5, UGT1A6, P450R, ABCG2, GLUT5, PEPT1, MCT1, 4F2 cell-surface antigen heavy chain (4F2hc), LAT2, OSTα, and OSTß showed intermediate levels (1-10 fmol/µg protein), and CYP1A1, CYP1A2, CYP1B1, CYP2C18, CYP2C19, CYP2J2, CYP3A7, CYP4A11, CYP51A1, UGT1A3, UGT1A4, UGT1A8, UGT2B4, ABCC1, ABCC4, ABCC5, ABCC6, ABCG8, TAUT, OATP2A1, OATP2B1, OATP3A1, OATP4A1, OCTN1, CNT2, PCFT, MCT4, GLUT4, and SLC22A18 showed low levels (less than 1 fmol/µg protein). The greatest interindividual difference (364-fold) was detected for UGT2B17. However, differences in expression levels of other quantified UGTs (except UGT2B15 and UGT2B17), CYPs (except CYP1A1 and CYP3A5), and P450R, and all quantified transporters, were within 10-fold. Expression levels of CYP1A2 and GLUT4 were significantly correlated with body-mass index. The levels of 4F2hc showed significant gender differences. Smokers showed increased levels of UGT1A1 and UGT1A3. These findings provide a basis for understanding the changes in molecular mechanisms of jejunal metabolism and transport, as well as their interindividual variability, in morbidly obese patients.

Absorption and efficacy of acetylsalicylic acid in patients with short bowel syndrome.

BACKGROUND: The patients with a short bowel (SB) frequently require antiplatelet therapy. Resection of the bowel is likely to modify the absorption and first-pass effect of drugs. No data on the absorption and efficacy of the cardiovascular dose of aspirin (75-160 mg) in these patients have been published. OBJECTIVE: To evaluate the efficacy of a low dose of aspirin in patients with SB caused by mesenteric ischemia. METHODS: The efficacy of a low dose of aspirin was assessed in 10 consecutive SB patients, both 1 hour and 24 hours after administration (peak and trough value, respectively). The primary criterion was the inhibition of platelet aggregation, as assessed by light transmission aggregometry, triggered with 0.5 mg/mL arachidonic acid. Biological efficacy of aspirin was also evaluated by serum thromboxane B2 value and by platelet function analyzer-100. RESULTS: At its peak value, aspirin had the expected efficacy, as demonstrated both by light transmission aggregometry and the other methods. However, 24 hours after administration, as many as 30% of patients had lost the pharmacological efficacy of their aspirin. CONCLUSION: We show for the first time that with at least 30 cm of small intestine, all patients with SB absorb sufficient oral aspirin in a cardiovascular dose to rapidly exert the expected level of antiplatelet activity. But given only once daily, aspirin does not provide stable 24-hour antiplatelet protection in 30% of patients, because of increased platelet turnover, as usually observed in patients with extensive vascular pathology, diabetes, or inflammation.

[Use of oral drugs and short bowel syndrome: an analysis of practices]. / Utilisation des médicaments par voie orale et syndrome de grêle court : analyse des pratiques.

OBJECTIVE: To describe drug prescription patterns in patients with short bowel syndrome (SBS). METHODS: The drug prescriptions of patients suffering from SBS type 1 to 3 were compared. RESULTS: Seventy-nine percent of the drugs were prescribed by oral route, and this proportion was significantly higher in patients with type 3 compared to tose with type 1. Twenty-nine percent of prescriptions were dietary supplement-drugs, 14.3% were gastrointestinal drugs and 11.4% were cardiovascular drugs. Oral prescription medications for SBS concerned many drug categories. The number of gastrointestinal or dietary supplement drugs was comparable between the 3 types. Drug doses were not increased compared with the recommendations, except for gastrointestinal drugs. CONCLUSION: The oral administration is common and at usual dosage in patients with SBS despite a lack of studies on absorption that may help to individualize drug prescription.

Management of Pain Medication in Patients With a History of Bariatric Surgery: A Systematic Review.

CONTEXT: Obesity prevalence is persistently increasing worldwide. Among surgical therapeutic procedures, bypass surgery and sleeve gastrectomy have shown the best results regarding weight loss, prevention, and treatment of secondary complications. However, these surgeries are associated with an increased risk of malabsorption and metabolic changes that could further affect the pharmacokinetics of drugs. On the other hand, patients with a history of such surgeries are more likely to experience pain and request analgesic initiation or adaptation. The question of how to manage pain medication in these patients is challenging due to their narrow therapeutic indexes. OBJECTIVES: To summarize the current literature on the impact of bariatric surgery on the subsequent pharmacokinetics of analgesics and propose a multidisciplinary therapeutic attitude to optimize pain management in these patients. METHODS: We conducted a systematic review that included all pharmacological studies published after 2000. RESULTS: Unexpectedly, these surgeries seem to increase the bioavailability of drugs by long-term improvement of hepatic function. Yet, the medical community drastically lacks robust guidelines for pain management in those patients. This systematic review aims to bring together pharmacological studies related to the use of pain treatments in patients who underwent bypass surgery or sleeve gastrectomy. CONCLUSIONS: Caution should be exercised regarding the risk of overdose in every circumstance: treatment initiation, change of doses, or change of molecule. More prospective trials comparing the pharmacokinetics of medications in obese patients with and without prior bariatric surgery are needed.

Inadequate therapeutic response to a recommended antituberculosis fixed-dose combination regimen in an overweight patient with Mycobacterium bovis infection.

OBJECTIVE: To report a case of an overweight man with lymph node tuberculosis due to Mycobacterium bovis, a part of the Mycobacterium tuberculosis complex, treated with fixed-dose combination (FDC) chemotherapy. CASE REPORT: Following guidelines, according to the patient's weight (92 kg), we prescribed the maximum recommended doses of isoniazid-rifampin-pyrazinamide FDC. It led initially to underdosing, with a poor clinical outcome, justifying increased doses and a complex regimen using separate drugs (isoniazid 600 mg, rifampin 1200 mg, and levofloxacin 1000 mg) to achieve therapeutic drug concentrations and clinical response. DISCUSSION: Usually recommended doses of FDC chemotherapies may be inappropriate in overweight patients. We discuss here the different factors that may be involved in poor clinical outcomes, particularly the consequences of excess weight on drug metabolism: drug-drug interaction, FDC use, generic formulation use, intestinal malabsorption, and acetylation profile. CONCLUSIONS: Therapeutic drug monitoring in overweight patients may be useful in the clinical setting to help clinicians individualize drug therapeutic regimens and optimize drug response, adherence, and safety.

Phenotyping Indices of CYP450 and P-Glycoprotein in Human Volunteers and in Patients Treated with Painkillers or Psychotropic Drugs.

Drug-metabolizing enzymes and drug transporters are key determinants of drug pharmacokinetics and response. The cocktail-based cytochrome P450 (CYP) and drug transporter phenotyping approach consists in the administration of multiple CYP or transporter-specific probe drugs to determine their activities simultaneously. Several drug cocktails have been developed over the past two decades in order to assess CYP450 activity in human subjects. However, phenotyping indices were mostly established for healthy volunteers. In this study, we first performed a literature review of 27 clinical pharmacokinetic studies using drug phenotypic cocktails in order to determine 95%,95% tolerance intervals of phenotyping indices in healthy volunteers. Then, we applied these phenotypic indices to 46 phenotypic assessments processed in patients having therapeutic issues when treated with painkillers or psychotropic drugs. Patients were given the complete phenotypic cocktail in order to explore the phenotypic activity of CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP3A, and P-glycoprotein (P-gp). P-gp activity was evaluated by determining AUC0-6h for plasma concentrations over time of fexofenadine, a well-known substrate of P-gp. CYP metabolic activities were assessed by measuring the CYP-specific metabolite/parent drug probe plasma concentrations, yielding single-point metabolic ratios at 2 h, 3 h, and 6 h or AUC0-6h ratio after oral administration of the cocktail. The amplitude of phenotyping indices observed in our patients was much wider than those observed in the literature for healthy volunteers. Our study helps define the range of phenotyping indices with "normal" activities in human volunteers and allows classification of patients for further clinical studies regarding CYP and P-gp activities.

Cytochromes P450 and P-Glycoprotein Phenotypic Assessment to Optimize Psychotropic Pharmacotherapy: A Retrospective Analysis of Four Years of Practice in Psychiatry.

Altered cytochromes P450 enzymes (CYP) and P-glycoprotein transporter (P-gp) activity may explain variabilities in drug response. In this study, we analyzed four years of phenotypic assessments of CYP/P-gp activities to optimize pharmacotherapy in psychiatry. A low-dose probe cocktail was administered to evaluate CYP1A2, 2B6, 2D6, 2C9, 2C19, 3A4, and P-gp activities using the probe/metabolite concentration ratio in blood or the AUC. A therapeutic adjustment was suggested depending on the phenotyping results. From January 2017 to June 2021, we performed 32 phenotypings, 10 for adverse drug reaction, 6 for non-response, and 16 for both reasons. Depending on the CYP/P-gp evaluated, only 23% to 56% of patients had normal activity. Activity was decreased in up to 57% and increased in up to 60% of cases, depending on the CYP/P-gp evaluated. In 11/32 cases (34%), the therapeutic problem was attributable to the patient's metabolic profile. In 10/32 cases (31%), phenotyping excluded the metabolic profile as the cause of the therapeutic problem. For all ten individuals for which we had follow-up information, phenotyping allowed us to clearly state or clearly exclude the metabolic profile as a possible cause of therapeutic failure. Among them, seven showed a clinical improvement after dosage adaptation, or drug or pharmacological class switching. Our study confirmed the interest of CYP and P-gp phenotyping for therapeutic optimization in psychiatry.

Drug-induced meningitis: A review of the literature and comparison with an historical cohort of viral meningitis cases.

BACKGROUND: Drug-induced aseptic meningitis (DIAM) is potentially insufficiently considered by clinician, being of rare etiology, with there being no previously published exhaustive study describing its clinical and biological features. METHODS: Two independent academic clinicians searched all the case reports of DIAM from 1995 until 15th April, 2017. The search was limited to studies performed in humans, published in English or French. Clinical and biological data of subjects were compared with those of patients with documented viral meningitis. RESULTS: One hundred and fifty-one case reports fulfilled our inclusion criteria. Non-steroidal anti-inflammatory drugs were the commonest drug cause of AM n=49, followed by antibiotics n=46, biotherapy n=19 and finally immunomodulators n=15. The clinical and biological presentation of DIAM varies according to the causative etiological drug, especially with respect to the interval between exposure and presentation and cerebrospinal fluid (CSF) pleiocytosis. Clinical symptoms associated with meningitis were more prevalent in viral meningitis than in DIAM, except for fever and signs of encephalitis. Cerebrospinal fluid examination in DIAM reveals an increased CSF white cell count and an increased proportion of neutrophils and protein, compared with viral meningitis. DISCUSSION: We present an extensive review of the DIAM case reports, and highlight their clinical and biological characteristics according to the drugs involved. While comparing for the first time their characteristics with those of viral meningitis, this review hopes in facilitate earlier diagnosis and management of DIAM in clinical practice.

Evaluation of Phenotypic and Genotypic Variations of Drug Metabolising Enzymes and Transporters in Chronic Pain Patients Facing Adverse Drug Reactions or Non-Response to Analgesics: A Retrospective Study.

This retrospective study evaluates the link between an adverse drug reaction (ADR) or a non-response to treatment and cytochromes P450 (CYP), P-glycoprotein (P-gp) or catechol-O-methyltransferase (COMT) activity in patients taking analgesic drugs for chronic pain. Patients referred to a pain center for an ADR or a non-response to an analgesic drug between January 2005 and November 2014 were included. The genotype and/or phenotype was obtained for assessment of the CYPs, P-gp or COMT activities. The relation between the event and the result of the genotype and/or phenotype was evaluated using a semi-quantitative scale. Our analysis included 243 individual genotypic and/or phenotypic explorations. Genotypes/phenotypes were mainly assessed because of an ADR (n = 145, 59.7%), and the majority of clinical situations were observed with prodrug opioids (n = 148, 60.9%). The probability of a link between an ADR or a non-response and the genotypic/phenotypic status of the patient was evaluated as intermediate to high in 40% and 28.2% of all cases, respectively. The drugs in which the probability of an association was the strongest were the prodrug opioids, with an intermediate to high link in 45.6% of the cases for occurrence of ADRs and 36.0% of the cases for non-response. This study shows that the genotypic and phenotypic approach is useful to understand ADRs or therapeutic resistance to a usual therapeutic dosage, and can be part of the evaluation of chronic pain patients.