Fatality caused by a combined trimipramine-citalopram intoxication

Patterns of toxicity and factors influencing severity in acute adult trimipramine poisoning

AIMS

To analyze the clinical features of trimipramine poisoning, identify a minimal toxic dose, and the dose bearing a 50% risk of developing a moderate, severe or fatal outcome.

METHODS

All acute adult trimipramine monointoxications reported by physicians to the Swiss Toxicological Information Centre between January 1992 and December 2009 were identified.

RESULTS

Two hundred and thirty cases (26 confirmed and 204 probable) were analyzed, the mean age was 35.7 years and 74% were females. One hundred and thirty-seven patients showed mild, 54 moderate and 21 severe symptoms. Three cases were fatal due to refractory cardiovascular collapse. Ninety-three per cent of the events were attempted or completed suicides. The most common symptoms were central nervous system depression (79.2%), tachycardia (19.1%) and QT(c) prolongation (13.9%). The severity of poisoning depended significantly on the ingested dose (P < 0.001). The minimal dose for moderate symptoms was 250 mg (median dose 1.2 g) and 850 mg for severe symptoms (median dose 2.7 g). The dose for a 50% risk of developing a moderate, severe or fatal outcome was 5.11 g. In 38 patients early gastrointestinal decontamination was performed. Overall, these patients ingested higher trimipramine doses than the late- or not-decontaminated patients (P = 0.113). The median doses were also higher in the decontaminated group within each severity category except in the fatal cases.

CONCLUSIONS

We demonstrated that moderate trimipramine poisoning can already occur after ingestion of doses in the high therapeutic range. Poisoned patients have to be monitored for central nervous system depression, dysrhythmias and QT(c) prolongation. Early decontamination might be beneficial.

Case report of a fatal intoxication by citalopram

Citalopram is an antidepressant drug within the group of the selective serotonin reuptake inhibitors (SSRI). It is widely prescribed both in Europe and in United States, and it has always been considered a "safe" drug as pure intoxication with lethal outcome is rare, and most cases of overdose, even with high doses of citalopram ingested, are reported to have an uneventful course. We report the case of a young woman found dead at home. She had been prescribed citalopram by her family doctor 3 weeks before her death for a depressive syndrome. Police found in her house 3 empty blister packages of 28 citalopram tablets (20 mg) and 2 bottles of citalopram oral solution (4%, 15 mL each). The autopsy findings were unremarkable. Nasal swabs, blood from femoral vein, urine, bile and tissue samples were collected for toxicologic investigation. Citalopram separation was performed by solid/liquid method, using Bond-Elute columns. The extracts were analyzed by GLC and GC/MS methods. The toxicologic analysis showed high levels of citalopram in all the examined fluids and tissue samples (blood concentration: 11.60 mg/L). No other drugs and alcohol were detected. Our data confirm that if no other drug is involved, fatal complications occur only after ingestion of very high doses. However, there is no predefined "toxic dose," and the conditions under which the overdose occurs can be very important. We report the exact concentrations of the citalopram in the organs, and wethink that this can be useful in the cases where the blood samples were not available (ie, carbonized or decomposed body).

Routine therapeutic drug monitoring in patients treated with 10-360 mg/day citalopram

From data collected during routine TDM, plasma concentrations of citalopram (CIT) and its metabolites demethylcitalopram (DCIT) and didemethylcitalopram (DDCIT) were measured in 345 plasma samples collected in steady-state conditions. They were from 258 patients treated with usual doses (20-60 mg/d) and from patients medicated with 80-360 mg/d CIT. Most patients had one or several comedications, including other antidepressants, antipsychotics, lithium, anticonvulsants, psychostimulants and somatic medications. Dose-corrected CIT plasma concentrations (C/D ratio) were 2.51 +/- 2.25 ng mL-1 mg-1 (n = 258; mean +/- SD). Patients >65 years had significantly higher dose-corrected CIT plasma concentrations (n = 56; 3.08 +/- 1.35 ng mL-1 mg-1) than younger patients (n = 195; 2.35 +/- 2.46 ng mL-1 mg-1) (P = 0.03). CIT plasma concentrations in the generally recommended dose range were [mean +/- SD, (median)]: 57 +/- 64 (45) ng/mL (10-20 mg/d; n = 64), 117 +/- 95 (91) ng/mL (21-60 mg/d; n = 96). At higher than usual doses, the following concentrations of CIT were measured: 61-120 mg/d CIT, 211 +/- 103 (190) ng/mL (n = 93); 121-200 mg/d: 339 +/- 143 (322) ng/mL (n = 70); 201-280 mg/d: 700 +/- 408 (565) ng/mL (n = 18); 281-360 mg/d: 888 +/- 620 (616) ng/mL (n = 4). When only one sample per patient (at the highest daily dose if repeated dosages) is considered, there is a linear and significant correlation (n = 48, r = 0.730; P < 0.001) between daily dose (10-200 mg/d) and CIT plasma concentrations. In experiments with dogs, DDCIT was reported to affect the QT interval when present at concentrations >300 ng/mL. In this study, DDCIT concentration reached 100 ng/mL in a patient treated with 280 mg/d CIT. Twelve other patients treated with 140-320 mg/d CIT had plasma concentrations of DDCIT within the range 52-73 ng/mL. In a subgroup comprised of patients treated with > or =160 mg/d CIT and with CIT plasma concentrations < or =300 ng/mL, and patients treated with < or =200 mg/d CIT and CIT plasma concentrations > or = 600 ng/mL, the enantiomers of CIT and DCIT were also analyzed. The highest S-CIT concentration measured in this subgroup was 327 ng/mL in a patient treated with 140 mg/d CIT, but the highest S-CIT concentration (632 ng/mL) was measured in patient treated with 360 mg/d CIT. In conclusion, there is a highly linear correlation between CIT plasma concentrations and CIT doses, well above the usual dose range.

Effects of polymorphisms in CYP2D6, CYP2C9, and CYP2C19 on trimipramine pharmacokinetics

Little is known about the impact of cytochrome P450 polymorphisms on the metabolism of trimipramine, which is still widely used as antidepressant due to its positive effect on sleep patterns. A single oral dose of 75 mg trimipramine was given to 42 healthy volunteers selected according to their CYP2D6, CYP2C19, and CYP2C9 genotypes. The reference group included 8 subjects with homozygous active wild-type genotypes of all 3 enzymes (EM). This group was compared with 7 intermediate (IM) with 1 and 7 poor metabolizers (PM) with zero active alleles of CYP2D6 and CYP2C19, respectively, and with 4 subjects with the genotype CYP2C9*3/*3. Pharmacokinetics of trimipramine and its demethylated metabolite strongly depended on the CYP2D6 genotype. Median oral clearance of trimipramine was 276 L/h (range 180-444) in the reference group but only 36 L/h (range 24-48) in CYP2D6 PMs (P < 0.001). These differences could only be explained by an effect of CYP genotypes on both parameters, systemic clearance and bioavailability, the latter being at least 3-fold higher in CYP2D6 PMs than in the reference group. The desmethyltrimipramine area under the concentration-time curve was 40-fold greater in CYP2D6 PMs than in the reference group (1.7 vs. 0.04 mg/L x h in EMs), but below the quantification limit in most carriers of deficiencies of CYP2C19 or CYP2C9. This indicates that both CYP2C enzymes contribute to the demethylation of desmethyltrimipramine and CYP2D6 to further metabolism.

Toxicological interactions involving psychiatric drugs and alcohol: an update

This review focuses on the toxicological interactions between alcohol (ethanol) and psychiatric drugs (antidepressants and antipsychotics), including those leading to fatal poisoning. Acute or chronic ingestion of alcohol when combined with psychiatric drugs may lead to several clinically significant toxicological interactions. The metabolism of these drugs is generally but not always delayed by acute alcohol ingestion. Drugs undergoing metabolism may also show increased metabolic clearance with chronic alcohol ingestion. Therefore, the net effect may be influenced by internal (e.g. disease, age, gender), external (e.g. environment, diet) and pharmacokinetic (e.g. dose, timing of ingestion, gastrointestinal absorption, distribution and elimination) factors. Cases of fatal poisoning involving coadministration of psychiatric drugs, alcohol and other drugs prompted this review.

Review of pharmacokinetic and pharmacodynamic interaction studies with citalopram

Citalopram is a selective serotonin reuptake inhibitor that is N-demethylated to N-desmethylcitalopram partially by CYP2C19 and partially by CYP3A4 and N-desmethylcitalopram is further N-demethylated by CYP2D6 to the likewise inactive metabolite di-desmethylcitalopram. The two metabolites are not active. The fact that citalopram is metabolised by more than one CYP means that inhibition of its biotransformation by other drugs is less likely. Besides citalopram has a wide margin of safety, so even if there was a considerable change in serum concentration then this would most likely not be of clinical importance. In vitro citalopram does not inhibit CYP or does so only very moderately. A number of studies in healthy subjects and patients have confirmed, that this also holds true in vivo. Thus no change in pharmacokinetics or only very small changes were observed when citalopram was given with CYP1A2 substrates (clozapine and therophylline), CYP2C9 (warfarin), CYP2C19 (imipramine and mephenytoin), CYP2D6 (sparteine, imipramine and amitriptyline) and CYP3A4 (carbamazepine and triazolam). At the pharmacodynamic level there have been a few documented cases of serotonin syndrome with citalopram and moclobemide and buspirone. It is concluded that citalopram is neither the source nor the cause of clinically important drug-drug interactions.

Citalopram: a comprehensive review

Citalopram is a selective serotonin re-uptake inhibitor that has demonstrated antidepressant efficacy in numerous controlled clinical trials. Additional studies have shown that the drug benefits patients with other illnesses that are related in some way to serotonergic dysfunction, including anxiety, panic disorder, obsessive-compulsive disorder, premenstrual dysphoria, alcohol dependence and the behavioural disturbances of dementia. This paper reviews the full spectrum of citalopram's clinical efficacy, as well as its safety and tolerability, in a range of patients.