[Pharmacoresistance to psychotropic drugs in children and adolescents: Pharmacogenetic anomalies of cytochrome P450 2D6]

OBJECTIVES

Some patients in child and adolescent psychiatry present resistance to psychotropic drugs, often resulting in polytherapy, an increased risk of adverse events, and more frequent and longer hospitalisation. Psychotropic drugs are mainly metabolised in the liver, in particular by the CYP2D6 subunit of cytochrome P450. Anomalies such as a duplication of the CYP2D6 gene related to an ultra-rapid metaboliser phenotype has been described to be linked to clinical efficacy. However, little research has been done in child and adolescent psychiatry.

METHODS

A multi-centric cross-sectional study in the southeast of France explored the relation between pharmaco-resistance to psychotropic drugs and the prevalence of duplications or polymorphisms of CYP2D6 associated with an ultra-rapid phenotype in children and adolescents with severe mental health disease.

RESULTS

Twenty-two patients have been included. The presence of an ultra-rapid phenotype concerns one patient in our study. A second patient presents a slow metaboliser phenotype.

CONCLUSIONS

This study allows a clinical characterisation of the population of pediatric drug-resistant patients whose severity and the impact of their pathology are major and require long-term care associated with repeated hospitalisations, multiple drug prescriptions and numerous side effects. However, a link between drug resistance to psychotropic drugs and CYP2D6 UFM abnormalities could not be confirmed. An additional pharmacogenetic analysis by a panel of genes applied in the metabolism, transport and action of psychotropic drugs should be considered to answer questions about the resistance and independent effects of CYP2D6.

[Carbamazepine and psychotropic treatment interaction: Two case studies of carbamazepine overdosage]

Drug interaction is a frequent situation in pediatrics and child psychiatry. Carbamazepine (CBZ) is an antiepileptic drug used as a mood stabilizer in child psychiatry. CBZ is known to be a potent inducer of various CYP isoenzymes of cytochrome P450, which might result in a decrease in the plasma concentration of associated treatments. We describe two cases of CBZ overdosage in adolescent inpatients (14 and 16 years). The patients were treated with risperidone associated with fluoxetine in one and with loxapine in the other case, and CBZ was introduced as a mood stabilizer. Patients presented typical clinical symptoms (fatigue, dizziness, gastrointestinal signs, blurred vision). Overdosage was confirmed by an elevated CBZ plasma concentration (17 and 15.5 mg/L, therapeutic range 4-12 mg/L). We recommend introducing CBZ very progressively in patients treated with psychotropics, particularly when it is associated to several treatments. An intensification of clinical and biological follow-up with early plasma concentration testing should allow for better treatment adjustment.

[Follow-up of a 16-year-old adolescent with early-onset schizophrenia and catatonic symptoms]

INTRODUCTION

The aim of this paper is to underline the need of a systematic monitoring (1) of atypical antipsychotics and (2) of catatonic symptoms in child psychiatry. We present in this paper the clinical history of a 16-year-old adolescent inpatient needing a prescription of atypical antipsychotic drug. We present the most relevant results of our clinical monitoring over 7 months.

CASE REPORT

A 16-year-old Caucasian male adolescent, by the name of Paul, was admitted in August 2009 to an Adolescent University Psychiatry Unit for an acute psychotic disorder. On admission, he presented paranoid delusion, auditory hallucinations and impulsive movements. The score on the Bush-Francis Catatonia Rating Scale (BFCRS) was 17 (the threshold score for the diagnosis of catatonic symptoms is 2). Laboratory tests showed the lack of blood toxic levels, creatine phosphokinase (CPK) level was 684 IU/L. Paul was treated with clonazepam (0.05 mg/kg/d). This particular day was considered to be day #1 of the clinical drug monitoring. Immediately after, regular follow-up of catatonic symptoms was performed. On day #15, the CPK level returned to normal with improvement of clinical catatonia but with still a score of 4 on the BFCRS scale. Auditory hallucinations and delusion persisted. Risperidone treatment was begun (1mg/d and 1.5mg/d after 24 hours), associated with oral clonazepam (0.05 mg/kg/d). On day #17, after 48 hours of improvement of delusion, the catatonic symptoms rapidly worsened. Risperidone was stopped; Paul was transferred to intensive care where he was treated with clonazepam IV (0.1mg/kg/d). The score on BFCRS scale was 20, Paul presented no fever and the CPK level was below 170 IU/L. The diagnosis was a relapse of the catatonic episode, which was caused by the administration of risperidone. On day #24, no improvement in the state of catatonia was obtained. The treatment was changed with the following combination of medicine: clonazepam (0.1mg/kg/d)-lorazepam (5mg/d)-carbamazepine (10mg/kg/d). With this combination, the state of catatonia improved quickly and on day #31, he was transferred to the adolescent psychiatry unit. However, delusion and hallucinations persisted; a treatment with olanzapine was started at 5mg/d and then progressively increased to 20mg/d for 10 days. On day #115, after 3 months with olanzapine, no improvement of the hallucinatory and delusional symptoms was observed; the diagnosis of early-onset refractory schizophrenia was established. The Therapeutic Drug Monitoring (TDM) confirmed the good compliance; clozapine was introduced and progressively increased up to 250 mg/d. On day #199, after 3 months under clozapine (250 mg/d), the speech was coherent and delusion was rare. During this period, no relapse of the catatonic state was observed.

DISCUSSION

In this case, the BFCRS scale was sensitive to catatonic symptom diagnosis. CPK levels vary differently for each atypical antipsychotic and are not a specific complication indicator. In complex cases, the TDM seems useful when choosing atypical antipsychotics.

CONCLUSION

The association of two benzodiazepines (clonazepam-lorazepam) with carbamazepin allowed the improvement of catatonic symptoms. Plasma levels of atypical antipsychotics helped the practitioner in deciding the type of care required: plasma levels confirmed the patient's treatment adherence and thus reinforced the choice of clozapine.