Ketamine and its enantiomer S‐ketamine (esketamine) are known to produce rapid‐onset antidepressant effects in major depression. Intranasal esketamine has recently come onto the market as an antidepressant. Besides experience from short‐term use in anaesthesia and analgesia, the experience with ketamine as long‐term medication is rather low. The use of ketamine and esketamine is limited due to potential neurotoxicity, psychotomimetic side effects, potential abuse and interindividual variability in treatment response including cessation of therapy. Therefore, taking a look at individual patient risks and potential underlying variability in pharmacokinetics may improve safety and dosing of these new antidepressant drugs in clinical practice.Differential drug metabolism due to polymorphic cytochrome P450 (CYP) enzymes and gene‐drug interactions are known to influence the efficacy and safety of many drugs. Ketamine and esketamine are metabolized by polymorphic CYP enzymes including CYP2B6, CYP3A4, CYP2C9 and CYP2A6. In antidepressant drug therapy, usually multiple drugs are administered which are substrates of CYP enzymes, increasing the risk for drug–drug interactions. We reviewed the potential impact of polymorphic CYP variants and common drug–drug interactions in antidepressant drug therapy affecting ketamine pharmacokinetics, and the role for dose optimization. The use of ketamine or intranasal esketamine as antidepressants demands a better understanding of the factors that may impact its metabolism and efficacy in long‐term use. In addition to other clinical and environmental confounders, prior information on the pharmacodynamic and pharmacokinetic determinants of response variability to ketamine and esketamine may inform on dose optimization and identification of individuals at risk of adverse drug reactions.

Aims: Older patients in particular suffer from adverse drug reactions (ADR) when presenting in the emergency department. We aimed to characterise the phenotype of those ADRs, to be able to recognise an ADR in older patients.Methods: Cases of ADRs in emergency departments collected within the multicentre prospective observational study (ADRED) were analysed (n = 2215). We analysed ADR‐associated diagnoses, symptoms and their risk profiles. We present frequencies and odds ratios (OR) with 95% confidence intervals for adults (18–64 years) compared to older adults (≥65 years; young–old 65–79, old–old ≥80 years) and regression coefficients (B) for each year of age.Results: Most prominent differences were seen for drug‐associated confusion, dehydration, and bradycardia (OR 6.70 [1.59–28.27], B .054; OR 6.02 [2.41–15.03], B .081, and 4.82 [2.21–10.54], B .040), more likely seen in older adults. Bleedings were reported in all age groups, but gastrointestinal bleedings occurred with more than doubled chance in older adults (OR 2.46 [1.77–3.41], B .030), likewise did other bleedings such as haemorrhage from respiratory passages (OR 2.89 [1.37–6.11], B.036). Falls were more likely in older adults (OR 2.84 [1.77–4.53], B .030), while dizziness was frequent in both age groups.Conclusion: Our data point to differences in symptoms of ADRs between adults and older individuals, with dangerous drug‐associated phenomena in the older adult such as bleedings or falls. Physicians should consider drug‐associated origins of symptoms in older adults with an increased risk for serious health problems.

Individual differences in required drug dosages exist based on the pharmacogenomic (PGx) profiles. This study aimed to assess associations between PGx profiles and adverse drug reactions (ADR) that lead to admissions to the emergency department (ED). ADR cases of the prospective multi-center observational trial in EDs (ADRED study) were analyzed (n = 776) together with the relevant PGx phenotypes of the enzymes CYP2D6, CYP2C19, CYP2C9, and VKORC1. Overall, the allele frequency distribution in this cohort did not differ from the population frequencies. We compared the frequencies of phenotypes in the subgroups with the drugs suspected of certain ADR, in the remaining cases. The frequency distribution of CYP2C19 differed for the ADR bleeding cases suspected of clopidogrel (p = 0.020). In a logistic regression analysis, higher CYP2C19 activity (OR (95% CI): 4.97 (1.73−14.27)), together with age (1.05 (1.02−1.08)), showed an impact on the clopidogrel-suspecting ADRs, when adjusting for the clinical parameters. There was a trend for an association of phenprocoumon-risk profiles (low VKORC1 or CYP2C9 activity) with phenprocoumon-suspecting ADRs (p = 0.052). The PGx impact on serious ADRs might be highest in drugs that cannot be easily monitored or those that do not provoke mild ADR symptoms very quickly. Therefore, patients that require the intake of those drugs with PGx variability such as clopidogrel, might benefit from PGx testing.

Aims: Phenoconversion, a genotype‐phenotype mismatch, challenges a successful implementation of personalized medicine. The aim of this study was to detect and determine phenoconversion using the solanidine metabolites 3,4‐seco‐solanidine‐3,4‐dioic acid (SSDA) and 4‐OH‐solanidine as diet‐derived cytochrome P450 2D6 (CYP2D6) biomarkers in a geriatric, multimorbid cohort with high levels of polypharmacy. Methods: Blood samples and data of geriatric, multimedicated patients were collected during physician counsel (CT: NCT05247814). Solanidine and its metabolites were determined via liquid chromatography/tandem mass spectrometry and used for CYP2D6 phenotyping. CYP2D6 genotyping was performed and activity scores (AS) were assigned. Complete medication intake was assessed. A shift of the AS predicted via genotyping as measured by phenotyping was calculated. Results: Solanidine and its metabolites were measured in 88 patients with complete documentation of drug use. Patients had a median age of 83 years (interquartile range [IQR] 77‐87) and the majority (70.5%, n = 62) were female. Patients took a median of 15 (IQR 12‐17) medications. The SSDA/solanidine metabolic ratio correlated significantly with the genotyping‐derived AS ( P < .001) and clearly detected poor metabolizers. In the model adjusted for age, sex, Charlson Comorbidity Index and estimated glomerular filtration rate each additional CYP2D6 substrate/inhibitor significantly lowered the expected AS by 0.53 (95% confidence interval 0.85‐0.21) points in patients encoding functional CYP2D6 variants ( R ² = 0.242). Conclusions: Phenotyping of CYP2D6 activity by measurement of diet‐derived biomarkers elucidates phenoconversion in geriatric patients. These results might serve as a prerequisite for the validation and establishment of a bedside method to measure CYP2D6 activity in multimorbid patients for successful application of personalized drug prescribing.

CYP2D6 is involved in the metabolism of many drugs. Its activity is affected by pharmacogenetic variability leading to highly polymorphic phenotypes between individuals, affecting safety and efficacy of drugs. Recently, solanidine, a steroidal alkaloid from potatoes, and its metabolites, has been identified as a dietary‐derived activity marker for CYP2D6. The intraday variability in plasma within individuals has not been studied yet in healthy subjects. As part of a CYP phenotyping cocktail study with 20 healthy participants, plasma concentrations of solanidine, 4‐OH‐solanidine and 3,4‐secosolanidine‐3,4‐dioic acid (SSDA) were determined using a sensitive liquid chromatography‐mass spectrometry method in urine and in plasma at timepoints 0, 2.5, 5, 8, and 24 hours after intake of test substances. The participants were phenotyped for CYP2D6 with oral metoprolol (12.5 mg) with 15 plasma sampling points over 24 hours (DRKS00028922). Metabolic ratios (MRs) of metabolite to parent plasma concentrations were formed from single timepoints and the area under the curve (AUC). All participants were genotyped for CYP2D6. The intra‐individual variability of the CYP2D6 metabolite SSDA was highly stable with a median SD of 11.62% over 24 hours. MR SSDA/solanidine was more variable (median SD 31.90%) but correlated significantly at all measured timepoints with AUC MR α‐OH‐metoprolol/metoprolol. The AUC MR SSDA/solanidine showed a significant linear relationship with the genetically predicted CYP2D6 activity score. This study substantiates the MR SSDA/solanidine as CYP2D6 activity marker. The high correlation with metoprolol MR indicates a valid prediction of the CYP2D6 phenotype at any timepoint during the study day.

Introduction The prevalence of psychotropic drug use in our society is increasing especially in older adults, thereby provoking severe adverse drug reactions (ADR). To identify specific patient risk profiles associated with psychotropic drug use in the situation of polymedication. Methods Cases of ADRs in general emergency departments (ED) collected within the multi-center prospective observational study (ADRED) were analyzed (n=2215). We compared cases with use of psychotropic drugs and without concerning their clinical presentation at the ED. Results A third of patients (n=731, 33%) presenting to the ED with an ADR took at least 1 psychotropic drug. Patients with psychotropic drug use tended to be older, more often female, and took a higher number of drugs (all p<0.001). The frequency of falls was almost 3 times higher than compared to the non-psychotropic drug group (10.5 vs. 3.9%, p<0.001), and similar syncope was also more often seen in the psychotropic drug users (8.8 vs. 5.5%, p=0.004). The use of psychotropic drugs increased the risk for falls by a factor of 2.82 (OR, 95% CI (1.90–4.18)), when adjusting for gender, age, numbers of pre-existing diseases, and drugs, respectively. Discussion The association of psychotropic drug use with fall and syncope in combination with polymedication and older age leads to the suspicion that psychotropic drugs might be potentially harmful in specific risk populations such as older adults. It may lead us to thoroughly weigh the benefit against risk in a patient-oriented way, leading to an integrative personalized therapy approach.