Clinically significant interactions of psychotropic agents with antipsychotic drugs

Studies on some neuropharmacological properties of Nevirapine in mice

Nevirapine (NVP) is non-nucleoside reverse transcriptase inhibitor and an anti-retroviral drug (ARV) with the highest BBB penetrating ability. Its specific pharmacologic effects on central nervous system (CNS) are not well known. The objective of the study was to investigate some CNS effects of Nevirapine. Oral acute toxicity test (Lorke, 1983) was used to estimate the LD₅₀. Exploratory or sedative effects were tested using open field test(OFT), Hole-board test (HBT), diazepam-induced sleeping time test, and ketamine-induced sleeping time test. Five groups of mice were used (5 mice /group). The negative control group received vehicle (distilled water) (10 mL /kg) while groups II, III, and IV received NVP- 15.625 mg/kg, 31.25 mg/kg, 62.5 mg/kg body weight respectively while group V received 0.25 mg/kg of diazepam intraperitoneal. Groups I to IV were treated orally. The oral LD₅₀ was determined to be 2154. 07 mg/kg. NVP, in a dose dependent fashion, increased the number of line-crossing in the OFT. Also, NVP in a dose-dependent fashion, significantly reduced the duration of diazepam-induced sleeping time as well as delayed onset. NVP significantly potentiated ketamine-induced sleeping time duration. Nevirapine possess excitatory effects possibly through antagonism of GABA receptors. Nevirapine causes wakefulness (shortening of sleep) possibly via antagonism of GABAergic neurotransmission.

Changes in medication practices for hospitalized psychiatric patients: 2009 versus 2004

BACKGROUND

We tested the hypothesis that combinations and total daily doses of psychotropics for hospitalized patients diagnosed with major psychiatric disorders are rising.

METHODS

We evaluated McLean Hospital records of 481 consecutive inpatients with DSM-IV schizophrenia, schizoaffective, or bipolar disorders in 2004 (n = 278) or 2009 (n = 203) to compare characteristics and treatments.

RESULTS

In 2009, Clinical Global Impression (CGI)-severity scores were 6% lower at intake and improved 1.7 times more than in 2004, as hospitalization-length decreased by 12%. Polytherapy (> or = 2 psychotropics) increased in 2009 (affective or schizoaffective disorders > schizophrenia). Total psychotropics/patient (3.1-3.2) remained stable but mood-stabilizers/patient increased markedly and antipsychotics/patient decreased somewhat in 2009. Antipsychotic-choice (2009) ranked: quetiapine, aripiprazole, risperidone, and others; mood-stabilizers ranked: lamotrigine, valproate, lithium, and others (1/4 off-label). In 2009, final total antipsychotic doses (mg/day) increased by 97%, and mood-stabilizers by 75%. Adverse-effect rates fell by half. Factors differing independently for 2009 versus 2004 ranked: (a) more CGI improvement, (b) more mood-stabilizers/patient, (c) lower admission CGI scores, and (c) higher total antipsychotic dose.

COMMENT

Combinations and doses of antipsychotic and mood-stabilizing drugs for inpatients increased markedly (2004 vs. 2009) without consistent correspondence of agents/person and doses, without apparent increase in major adverse effects, and with possibly superior clinical improvement.

Clozapine and sulpiride but not haloperidol or olanzapine activate brain DNA demethylation

Cortical GABAergic dysfunction, a hallmark of both schizophrenia (SZ) and bipolar (BP) disorder pathophysiologies may relate to the hypermethylation of GABAergic gene promoters (i.e., reelin and GAD67). Benefits elicited by a combination of atypical antipsychotics with valproate (VPA) (a histone deacetylase inhibitor that may also activate brain DNA demethylation) in SZ or BP disorder treatment prompted us to investigate whether the beneficial action of this association depends on induction of a putative DNA demethylase activity. To monitor this activity, we measured the ratio of 5-methyl cytosine to unmethylated cytosine in reelin and GAD67 promoters in the mouse frontal cortex and striatum. We compared normal mice with mice pretreated with l-methionine (5.2 mmol/kg s.c. twice a day for 7 days) to hypermethylate promoters, including reelin and GAD67. Clinically relevant doses of clozapine (CLZ) (3.8 to 15 micromol/kg twice a day s.c. for 3 days) and sulpiride (SULP) (12.5 to 50 micromol/kg twice a day for 3 days) but not clinically relevant doses of haloperidol (HAL) (1.3 to 4 micromol/kg twice a day s.c. for 3 days) or olanzapine (OLZ) (4 to 15 micromol/kg twice a day for 3 days) exhibited dose-related increases in the cortical and striatal demethylation of hypermethylated reelin and GAD67 promoters. These effects of CLZ and SULP were dramatically potentiated by a clinically relevant VPA dose (0.5 mmol/kg twice a day for 3 days). By activating a DNA demethylase, the association of CLZ or SULP with VPA may facilitate a chromatin remodeling that normalizes the GABAergic gene expression down-regulation detected in the telencephalic regions of SZ and BP patients.

Antipsychotic drugs alter neuronal development including ALM neuroblast migration and PLM axonal outgrowth in Caenorhabditis elegans

Antipsychotic drugs are increasingly being prescribed for children and adolescents, and are used in pregnant women without a clear demonstration of safety in these populations. Global effects of these drugs on neurodevelopment (e.g., decreased brain size) have been reported in rats, but detailed knowledge about neuronal effects and mechanisms of action are lacking. Here we report on the evaluation of a comprehensive panel of antipsychotic drugs in a model organism (Caenorhabditis elegans) that is widely used to study neuronal development. Specifically, we examined the effects of the drugs on neuronal migration and axonal outgrowth in mechanosensory neurons visualized with green fluorescent protein expressed from the mec-3 promoter. Clozapine, fluphenazine, and haloperidol produced deficits in the development and migration of ALM neurons and axonal outgrowth in PLM neurons. The defects included failure of neuroblasts to migrate to the proper location, and excessive growth of axons past their normal termination point, together with abnormal morphological features of the processes. Although the antipsychotic drugs are potent antagonists of dopamine and serotonin receptors, the neurodevelopmental deficits were not rescued by co-incubation with serotonin or the dopaminergic agonist, quinpirole. Other antipsychotic drugs, risperidone, aripiprazole, quetiapine, trifluoperazine and olanzapine, also produced modest, but detectable, effects on neuronal development. This is the first report that antipsychotic drugs interfere with neuronal migration and axonal outgrowth in a developing nervous system.

Lithium Intoxication Associated With Intramuscular Ziprasidone in Schizoaffective Patients

Antipsychotic agents have been used for the treatment of mood disorders in schizophrenic and schizoaffective patients. It has also been suggested that combinations of lithium and antipsychotics may be more effective than either class alone in treatment of schizoaffective patients. Lithium is known to interact with a variety of medications, including conventional and atypical antipsychotics. Although these combinations are generally well tolerated, they may sometimes lead to various adverse side effects. The authors report two schizoaffective patients with manic psychotic state and psychomotor agitation treated with lithium. Both patients developed symptoms of lithium intoxication after intramuscular ziprasidone treatment. To the best of their knowledge, this is the first description of such an adverse effect of this new atypical neuroleptic drug. They assume that lithium intoxication in the two presented cases was associated with the fast increase of ziprasidone serum level after its parenteral application, possibly affecting lithium excretion and thereby leading to lithium intoxication.

Potential role of cerebral cytochrome P450 in clinical pharmacokinetics: modulation by endogenous compounds

Cytochrome P450 (CYP) enzymes catalyse phase I metabolic reactions of psychotropic drugs. The main isoenzymes responsible for this biotransformation are CYP1A2, CYP2D6, CYP3A and those of the subfamily CYP2C. Although these enzymes are present in the human brain, their specific role in this tissue remains unclear. However, because CYP enzymatic activities have been reported in the human brain and because brain microsomes have been shown to metabolise the same probe substrates used to assess specific hepatic CYP activities and substrates of known hepatic CYPs, local drug metabolism is believed to be likely. There are also indications that CYP2D6 is involved in the metabolism of endogenous substrates in the brain. This, along with the fact that several neurotransmitters modulate CYP enzyme activities in human liver microsomes, indicates that CYP enzymes present in brain could be under various regulatory mechanisms and that those mechanisms could influence drug pharmacokinetics and, hence, drug response. In this paper we review the presence of CYP1A2, CYP2C9, CYP2D6 and CYP3A in brain, as well as the possible existence of local brain metabolism, and discuss the putative implications of endogenous modulation of these isoenzymes by neurotransmitters.

Pharmacokinetic Factors in the Adverse Cardiovascular Effects of Antipsychotic Drugs

Antipsychotics may cause serious adverse cardiovascular effects, including prolonged QT interval and sudden death. This review considers antipsychotic-induced cardiovascular events from three perspectives: high-risk drugs, high-risk individuals and high-risk drug interactions. Pharmacokinetic drug interactions involving the cytochrome P450 (CYP) enzymatic pathway and pharmacodynamic interactions leading to direct cardiotoxic effects are discussed. Original reports on antipsychotic-induced drug interactions are reviewed, with consideration of management guidelines. The literature was reviewed from 1 January 1966 to 1 February 2002. The literature search revealed only 12 original articles published on antipsychotic drug interactions leading to cardiovascular adverse events. Only 4 of the 12 reports were prospective studies; the remainder were either retrospective or anecdotal.Although poor study designs preclude a definitive statement, it appears that pharmacokinetic interactions primarily involved the CYP2D6 and CYP3A4 enzymatic pathways. Those involving the CYP2D6 isozyme included interactions with tricyclic antidepressants, selective serotonergic reuptake inhibitors and beta-blockers. Among these drug interactions, tricyclic antidepressants were most likely to reach clinical significance because of their limited therapeutic index. Drug interactions related to the CYP3A4 pathway were generally less severe, and involved high-potency antipsychotics coadministered with inhibitors such as clarithromycin. Strategies are discussed for the management of adverse cardiovascular events related to antipsychotic drug interactions, including the use of an algorithm. Large, randomised, placebo-controlled studies with strict inclusion criteria are needed to determine the role that antipsychotics play in QT prolongation and sudden death.

Insuffisances cardiaques d’origine médicamenteuse (en dehors des anthracyclines)

The principal drugs implicated in or disclosing cardiac insufficiency are drawn from a review of the literature and observations by the French national pharmacovigilance database, from 1984 to April 2003. Several pharmacological classes are identified: in addition to antimitotic drugs, such as anthracyclines, many drugs are implicated in cardiac insufficiency, e.g. immunomodulators, anti-inflammatory drugs (including coxibs), antiarrhythmic drugs, anaesthetic drugs, antipsychotic drugs, and antidiabetic drugs (including glitazones). It is usual to classify these drugs according to three categories: (i) drugs likely to cause cardiac insufficiency de novo (such as cyclophosphamide, paclitaxel, mitoxantrone, interferons, interleukin-2 etc.); (ii) drugs likely to worsen preexisting cardiac insufficiency (such as antiarrhythmics, beta-blockers, calcium antagonists, nonsteroidal and steroidal anti-inflammatory drugs, sympathomimetic drugs etc.); and (iii) drugs only occasionally causing cardiac insufficiency. This review shows that this classification is, in fact, artificial. If cardiac toxicity is a constant concern when using antimitotic drugs or some immunomodulator drugs, it is advisable to exercise caution in the use of many other drugs when treating patients with cardiac insufficiency, even if the clinical situation is well controlled. In particular, drug-drug interactions and patient medical history must be taken into account.

Multidisciplinary medication review in nursing home residents: what are the most significant drug-related problems? The Bergen District Nursing Home (BEDNURS) study

AIM

Based on a multidisciplinary review of drug use in nursing home residents, this study aimed to identify the most frequent clinically relevant medication problems and to analyse them according to the drugs involved and types of problems.

METHODS

Cross sectional study auditing drug use by 1354 residents in 23 nursing homes in Bergen, Norway. Data were collected in 1997. A physician/pharmacist panel performed a comprehensive medication review with regard to indications for drug use and active medical conditions. The drug related problems were subsequently classified according to the drugs involved and types of problems (indication, effectiveness, and safety issues).

RESULTS

2445 potential medication problems were identified in 1036 (76%) residents. Psychoactive drugs accounted for 38% of all problems; antipsychotics were the class most often involved. Multiple psychoactive drug use was considered particularly problematic. Potential medication problems were most frequently classified as risk of adverse drug reactions (26%), inappropriate drug choice for indication (20%), and underuse of beneficial treatment (13%).

CONCLUSIONS

Three of four nursing home residents had clinically relevant medication problems, most of which were accounted for by psychoactive drugs. The most frequent concerns were related to adverse drug reactions, drug choice, and probable undertreatment.

Progress defined--short-term efficacy, long-term effectiveness

The management of schizophrenia continues to represent an enormous challenge, despite improvements in both drug therapy and family and community interventions. Treatment expectations have shifted from the primary goal of controlling positive symptoms to a more comprehensive approach, with the aim of providing relief in all symptom domains, preventing relapses, improving compliance and ultimately improving functional outcomes in patients with schizophrenia. The advent of a new generation of 'atypical' antipsychotics should aid clinicians in meeting these goals. These agents combine high antipsychotic efficacy with improved tolerability profiles, mainly through a low liability for extrapyramidal symptoms. There is enough evidence from randomized, double-blind trials to demonstrate efficacy of atypical antipsychotics in improving global psychopathology, positive, negative, affective and cognitive symptoms, as well as preventing relapse during long-term use. These drugs may, therefore, provide clinicians with a new and important addition for first-line management of schizophrenia.

Cardiovascular adverse effects of antipsychotic drugs

Minor cardiovascular adverse effects from antipsychotic drugs are extremely common. They include effects such as postural hypotension and tachycardia due to anticholinergic or alpha1-adrenoceptor blockade, and may occur in the majority of patients at therapeutic dosages. There are a number of pharmacological effects that are of uncertain clinical significance, such as blockade of calmodulin, sodium and calcium channels and alpha2-adrenoceptors in the central nervous system. The most serious consequences of treatment, arrhythmias and sudden death, are probably uncommon and are most likely to be caused primarily by blockade of cardiac potassium channels such as HERG. Incomplete evidence suggests that arrhythmias and sudden death are a particular problem with certain drugs (thioridazine and droperidol), high risk populations (elderly, pre-existing cardiovascular disease, inherited disorders of cardiac ion channels or of antipsychotic drug metabolism) or people taking interacting drugs (such as drugs that prolong the QT interval, e.g. tricyclic antidepressants, drugs that inhibit antipsychotic drug metabolism, or diuretics). Clozapine may be unique in also causing death from myocarditis and cardiomyopathy. Much further research is required to more clearly identify high risk drugs and the populations that are at risk of sudden death, as well as the mechanisms involved and the extent of the risk.

The effect of carbamazepine on the steady-state pharmacokinetics of ziprasidone in healthy volunteers

AIMS

To evaluate the effect of steady-state carbamazepine administration on the steady-state pharmacokinetics of ziprasidone in healthy young adults, in an open, randomised, parallel-group study.

METHODS

Twenty-five subjects were randomized to one of two treatment groups. Group 1 received 20 mg ziprasidone twice daily on days 1 and 2, and a single dose on day 3. A single 100 mg dose of carbamazepine was given once daily on days 5 and 6 and twice daily on days 7 and 8, followed by 200 mg twice daily until day 28 and on the morning only on day 29. Ziprasidone 20 mg was also administered twice daily on days 26 and 27 and in the morning only on day 28. Group 2 received the same treatment regimen with carbamazepine replaced by placebo. Pharmacokinetic data were obtained on days 3 and 28.

RESULTS

Nine subjects in group 1 and 10 in group 2 completed all three treatment periods (ziprasidone, carbamazepine or placebo; and ziprasidone plus carbamazepine or placebo). Carbamazepine administration to group 1 was associated with modest reductions in ziprasidone exposure, with mean decreases in ziprasidone AUC(0,12 h) and Cmax values of 36% and 27%, respectively, on day 28 compared with day 3 (P<0.03). The mean differences between day 28 and day 3 ziprasidone AUC(0,12 h) and Cmax values were also statistically significantly greater in the carbamazepine group than in the placebo group. The mean half-life of ziprasidone decreased by 1 h from day 3 to day 28 in the subjects receiving carbamazepine, compared with virtually no change in the placebo group. All adverse events were mild or moderate in severity and there were no serious adverse events, or clinically significant changes in ECGs and vital signs throughout the study.

CONCLUSIONS

Induction of CYP3A4 with carbamazepine led to a modest reduction (<36%) in steady-state exposure to ziprasidone that is believed to be clinically insignificant.

Ziprasidone and the activity of cytochrome P450 2D6 in healthy extensive metabolizers

AIMS

To determine whether ziprasidone alters the metabolizing activity of the 2D6 isoenzyme of cytochrome P450 (CYP2D6).

METHODS

Twenty-four healthy young subjects aged 18-45 years were screened for CYP2D6 metabolizing activity and shown to be extensive metabolizers of dextromethorphan. These subjects were then randomized to receive a single dose of ziprasidone 80 mg, paroxetine 20 mg or placebo, 2 h before receiving a dose of dextromethorphan. Urine samples for the determination of dextromethorphan concentrations were collected over the 8 h period following dextromethorphan dosing, and used for the determination of dextromethorphan/dextrorphan ratios. Blood samples were collected immediately before and up to 10 h after the administration of ziprasidone or paroxetine, and used to derive pharmacokinetic parameters of ziprasidone and paroxetine.

RESULTS

There were no statistically significant changes in the urinary dextromethorphan/dextrorphan ratio in the ziprasidone group or the placebo group. By contrast, there was a 10-fold increase in the urinary dextromethorphan/dextrorphan ratio in the paroxetine group and this differed significantly from those in the ziprasidone and placebo groups (P = 0.0001).

CONCLUSIONS

The findings of this study suggest that ziprasidone does not inhibit the clearance of drugs metabolized by CYP2D6.

The effects of ziprasidone on steady-state lithium levels and renal clearance of lithium

AIMS

To assess the potential of ziprasidone to alter the renal clearance and steady-state serum levels of lithium.

METHODS

Healthy subjects who had stable serum lithium levels during the first 7 days of treatment with lithium 900 mg day(-1), given as two divided daily doses, were randomized to receive concomitant treatment with either ziprasidone, 40 mg day(-1), given as two divided daily doses, on days 9-11 followed by 80 mg day(-1), given as two divided daily doses on days 12-15 (n = 12), or placebo twice daily (n = 13). Ziprasidone or placebo was administered 2 h before each dose of lithium.

RESULTS

Ziprasidone administration was associated with a 0.07 mmol l(-1) (13%) mean increase in steady-state serum lithium levels compared with a mean increase of 0.06 mmol l(-1) (10%) with placebo. Mean renal clearance of lithium decreased by 0.09 l h(-1) (5%) in the ziprasidone group and by 0.14 l h(-1) (9%) in the placebo group. None of these differences between the two groups was statistically or clinically significant.

CONCLUSIONS

Ziprasidone does not alter steady-state serum lithium concentrations or renal clearance of lithium.

Interactions between anticonvulsant and psychoactive drugs

This review considers the relevance of pharmacokinetic interactions between antiepileptic drugs (AEDs) and psychoactive drugs in the treatment of mood disorders in patients with epilepsy. The determination of plasma levels of some of these drugs (mainly the AEDs) has enabled clinicians to evaluate the kinetic modifications during the course of such combined therapies and to adjusting the dosages in cases of subtherapeutic or toxic levels. In general, phenobarbital, phenytoin, and carbamazepine stimulate the catabolic degradation of tricyclic antidepressants (TCAs), and TCAs have an inhibitory effect on the elimination of AEDs. The newer antidepressants that selectively inhibit the reuptake of serotonin (SSRIs), although in different fashions for the different substances (fluoxetine, fluvoxamine, paroxetine) may cause an increase of plasma AED levels through inhibition of the isoenzyme P450 2D6. Similarly, antipsychotics (APs) are more rapidly metabolized when AEDs are co-administered, whereas AED metabolism is scarcely influenced by AP. Finally, plasma levels of tranquilizers are lowered by AED co-therapy. As the concomitant administration of AED and psychoactive drugs becomes increasingly used for treatment of mood disorders in patients with or without epilepsy, therapeutic drug monitoring may be useful in designing correct and rational therapy.

Effects of smoking, CYP2D6 genotype, and concomitant drug intake on the steady state plasma concentrations of haloperidol and reduced haloperidol in schizophrenic inpatients

The effects of smoking, CYP2D6 genotype, and concomitant use of enzyme inducers or inhibitors on the steady state plasma concentrations of haloperidol (HAL) and reduced haloperidol (RHAL) were evaluated in 92 schizophrenic inpatients. All but three of these patients received concomitant medication, in many cases with drugs potentially interacting with HAL. Of the 92 patients, 63 were treated orally with HAL in a daily dose of 0.4 to 50 mg; 29 patients were treated intramuscularly with a daily equivalent dose of HAL decanoate (expressed as HAL) of 1.8 to 17.9 mg. A wide interindividual variation in HAL dose and in steady state plasma concentrations of HAL and RHAL was observed. In the patients treated orally, the daily oral dose was about 4 times higher and the dose-normalized HAL (but not RHAL) plasma concentrations were significantly lower in smokers (n = 40) than in nonsmokers (n = 23) (p < 0.01). The dose-normalized RHAL (but not HAL) plasma concentrations and the RHAL/HAL ratio were significantly higher in poor metabolizers (PMs) than in extensive metabolizers (EMs). There was a trend toward an effect of potentially interacting drugs (inducers or inhibitors) on dose, dose-normalized HAL and RHAL plasma concentrations, and the RHAL/HAL ratio. In the patients treated intramuscularly, the dose-normalized HAL (but not RHAL) plasma concentrations were significantly lower in smokers than in nonsmokers, but no differences in doses were observed. This naturalistic study of modest sample size in a polymedicated population shows an effect of smoking and CYP2D6 genotype (and to a lesser extent, of interacting drugs) on the kinetics of HAL.

Drug-drug interactions in pediatric psychopharmacology

Serious consequences caused by drug-drug interactions continue to plague contemporary pharmacotherapy. The possibility of a drug-drug interaction should be suspected anytime a new or unexpected effect occurs that complicates the clinical management of a patient in the setting where the patient is receiving more than one drug. In this article, the authors address the mechanisms of pharmacokinetic-based drug-drug interactions focusing on important interactions that may occur with the common medications a pediatrician may prescribe to the child receiving psychoactive medication(s) prescribed by a child psychiatrist.

Effects of caffeine withdrawal from the diet on the metabolism of clozapine in schizophrenic patients

Both clozapine (CLZ) and caffeine are CYP1A2 substrates. This study raises the hypothesis of whether caffeine withdrawal from the diet alters the metabolism and/or clinical status of patients receiving CLZ. Seven schizophrenic patients (six men and one woman) receiving monotherapy with CLZ at 271+/-102 mg/day (3.73+/-1.4 mg/kg) participated in the study. CLZ, norclozapine (NOR), and clozapine-N-oxide (NOX) were assayed in plasma by high-performance liquid chromatography at three different time points: A, with concomitant intake of caffeine from the diet; B, after caffeine withdrawal for 5 days; and C, after 2 weeks of rechallenge to habitual caffeine intake. The CYP1A2 activity was determined by means of a urinary caffeine test. After a caffeine-free diet for 5 days, CLZ concentrations relative to time point A decreased from 486 to 306 ng/mL (-47%) (p < 0.02), NOX levels decreased from 66 to 49 ng/mL (-31%) (p < 0.03), and the NOR/CLZ ratio significantly increased from 0.47 to 1.04 (185%) (p < 0.02). All parameters returned to initial figures at time point C. The NOR/CLZ ratio was significantly correlated to the CYP1A2 index (rs = 0.96, p < 0.0005). In conclusion, changes in the habitual caffeine intake alter the metabolism of CLZ in schizophrenic patients. Thus, patient intake of caffeine should be medically supervised, and the monitoring of CLZ and metabolite levels may be warranted. Furthermore, in those patients who receive therapy with CLZ, the NOR/CLZ ratio may provide an additional and valuable estimate of CYP1A2 activity.