Effects of smoking on haloperidol and reduced haloperidol plasma concentrations and haloperidol clearance

Nonlinear pharmacokinetics of nefazodone after escalating single and multiple oral doses

The single- and multiple-dose pharmacokinetics of nefazodone and its metabolites, hydroxynefazodone, p-hydroxynefazodone, and m-chlorophenylpiperazine were investigated in two groups of 18 healthy male volunteers, employing three-period complete crossover designs. In one group, single 50-mg, 100-mg, and 200-mg oral doses of nefazodone hydrochloride were administered with a 1-week washout between treatments. In the other group, doses of 50 mg, 100 mg, and 200 mg were administered twice a day (every 12 hours) for 7.5 days (15 doses) with a 1-week washout between treatments. Serial plasma samples were obtained in both groups and assayed for nefazodone, hydroxynefazodone, m-chlorophenylpiperazine, and p-hydroxynefazodone. Cmax plasma levels of nefazodone and hydroxynefazodone were attained within 2 hours of administration of nefazodone; tmax for m-chlorophenylpiperazine was more delayed, and p-hydroxynefazodone levels were generally below the assay limit. On repeated twice-daily dosing of nefazodone, steady-state levels of the drug and its metabolites were reached within 3 days. Mean single-dose plasma half-life (t1/2) values for nefazodone increased from approximately 1 hour at a 50-mg dose to approximately 2 hours at a 200-mg dose; at steady state, t1/2 values increased from approximately 2 hours at 50 mg twice daily to approximately 3.7 hours at 200 mg twice daily. Whereas dose increased in the proportion of 1:2:4, mean single-dose AUC0-infinity for nefazodone increased in the proportion of 1:3.3:8.9 and mean steady-state AUC0-tau for nefazodone increased in the proportion of 1:4.2:16.8. Plasma levels of hydroxynefazodone paralleled those of nefazodone and were approximately 33% of nefazodone levels at each dose level. Plasma levels of m-chlorophenylpiperazine were only approximately 10% those of nefazodone. Within the dosage range of 50-200 mg of nefazodone hydrochloride, nefazodone and hydroxynefazodone exhibited nonlinear pharmacokinetics; m-chlorophenylpiperazine, a minor metabolite, appeared to exhibit linear pharmacokinetics.

Emergency treatment of psychotic symptoms. Pharmacokinetic considerations for antipsychotic drugs

Psychotic symptoms related to mental and medical disorders can pose a medical emergency. Selecting an appropriate antipsychotic medication to treat this emergency is based on the clinical situation, preferred route of administration, pharmacokinetic profile of the antipsychotic and the medications currently being taken by the patient. Intramuscular preparations are usually preferred over oral medication when the patients are not co-operative and require drugs with a faster onset of action and good bioavailability. High potency antipsychotics such as haloperidol and fluphenazine are effective in stabilising patients with psychotic symptoms quickly. Loxapine is an alternative when sedation is necessary and molindone is useful if a short-acting antipsychotic is required. Rapid neuroleptisation with intramuscular preparations of antipsychotic achieves therapeutic drug concentrations more rapidly, and also provides optimal control of psychotic symptoms. If the patient is cooperative, liquid oral preparations can be used; they are as effective as intramuscular formulations. If long term treatment with an antipsychotic in necessary and patients are stabilised, they can be switched from intramuscular to oral preparations. The oral dose is usually 1.5 to 5 times the total intramuscular dose per day, based on the bioavailability of the antipsychotic medication. If the patient is currently taking antipsychotic medication when the emergency situation occurs, it is usually adequate to increase the dose of antipsychotic drug. Appropriate dose adjustment or antipsychotic selection is necessary when drug interactions are expected. An in-depth knowledge of the pharmacokinetic profile and drug interaction profile of antipsychotic in necessary for the selection of the appropriate antipsychotic for any given emergency situation.

Medical disorders in the schizophrenic patient

OBJECTIVE

The primary purpose of this review of medical disorders in the schizophrenic patient is to provide the clinician interested in Consultation/Liaison psychiatry and psychosomatic issues a comprehensive and current review of the subject.

METHOD

The authors used the Index Medicus and Medline to find recent review articles and research articles related to medical disorders in the schizophrenic patient. Also, the authors described their clinical experience in Consultation/Liaison psychiatry working with schizophrenic patients in a large, tertiary-care academic medical center.

RESULTS

The authors divided their review into: 1) mortality and morbidity in schizophrenia, 2) differential diagnosis, 3) specific comorbidity management problems, 4) caring for schizophrenics on medical/surgical wards, and 5) antipsychotic drugs in the medical setting. Schizophrenia remains an important subject for Consultation/Liaison psychiatrists.

CONCLUSIONS

Schizophrenia and its protean manifestations confound the care of the medical patient. The psychosis of schizophrenia may impair the patient's capacity to recognize or articulate emerging medical illness, or to respond to therapeutic interventions. The psychiatrist caring for and consulting on patients with medical illnesses bears major responsibility for understanding the complex interface of schizophrenia and medical illnesses. Psychiatrists need to educate our medical and surgical colleagues how schizophrenia alters the usual presentation, clinical course, and response to treatment of common medical and surgical illnesses.

Clinical pharmacokinetics of antipsychotics

The antipsychotics are a chemically diverse group of heterocyclic compounds, which ameliorate many symptoms of schizophrenia. Most of the antipsychotics are very lipophilic and cross lipoidal membranes freely. When administered orally, they are well absorbed and undergo substantial pre-systemic elimination (bioavailability: 10-70%), are highly bound to plasma proteins (75-99%) and tissues, and are extensively distributed (VD: 100-1000 L). Primary route of elimination for most of antipsychotics is hepatic metabolism and biotransformation produces active metabolites. There is no linear relationship between the concentration of parent compound and different metabolites, and clinical relevance of pharmacologically active metabolites is not well understood. There are wide interindividual variabilities in pharmacokinetics, which result in large differences in steady-state plasma concentrations on the same dose regimen. The existence of optimal therapeutic ranges for most antipsychotics remains controversial. One of the major problems is the lack of well-designed studies that involve sufficient numbers of patients to clearly establish a therapeutic range for these drugs and is further complicated by the presence of a large number of pharmacologically active metabolites. However, the pronounced interindividual kinetic variabilities, combined with problems of noncompliance and drug interactions, and the delayed onset of clinical response in relation to initiation of treatment with antipsychotics are reasons why drug monitoring in conjunction with clinical status of the patient can be useful. Indications for antipsychotic drug monitoring include lack of response, non-compliance, toxicity, and drug interactions when other drugs are coadministered.

Treatment of schizophrenia: a clinical and preclinical evaluation of neuroleptic drugs

Forty years after the first clinical report on the effectiveness of chlorpromazine in psychiatric patients, neuroleptic drugs are still the most widely used drugs in the treatment of schizophrenia. Indeed, there are no other drugs which have proven to be as effective in the treatment of this severe psychiatric disorder. Yet, there are still many unresolved problems relating to neuroleptic drugs. The present review gives a comprehensive overview of our knowledge (and our lack of knowledge) with respect to the clinical and preclinical effects of neuroleptic drugs and tries to integrate this knowledge in order to identify the neuronal mechanisms underlying the therapeutic and side effects of neuroleptic drugs.

Nicotine blocks latent inhibition in rats: evidence for a critical role of increased functional activity of dopamine in the mesolimbic system at conditioning rather than pre-exposure

Latent inhibition (LI) is a cognitive process whereby repeated exposure of a stimulus without consequence impedes the formation of subsequent associations with that stimulus. A number of studies in the rat have reported that LI is impaired by moderate systemic doses of amphetamine, an effect believed to be mediated via dopamine (DA) release in the nucleus accumbens. We and others have reported that nicotine has a selective effect in releasing DA in the accumbens rather than the caudate nucleus. We have therefore examined the ability of nicotine to disrupt LI, using a conditioned emotional response paradigm. Pre-exposure of a tone stimulus impaired subsequent conditioning between that stimulus and mild footshock, as indexed by suppression of licking by the tone subsequently presented alone. This LI effect was prevented, by an effect confined to the pre-exposed group, by doses of 0.4 or 0.6 mg/kg nicotine SC, which are accumbens selective, given before pre-exposure and before conditioning. The effect of nicotine in disrupting LI was prevented by prior administration of haloperidol at a dose (0.5 mg/kg) reported to reverse the disruptive effect of amphetamine on LI. Although the amphetamine effect requires two administrations, the effect of two administrations of nicotine was reproduced by a single dose of nicotine given before conditioning, but not by a single dose before pre-exposure. The results are discussed in relation to studies in human control and schizophrenic subjects, which suggest that increased DA activity in humans is also associated with impaired LI.(ABSTRACT TRUNCATED AT 250 WORDS)

Normalization by nicotine of deficient auditory sensory gating in the relatives of schizophrenics

Diminished gating of the P50 auditory evoked response to repeated stimuli is a psychophysiological feature of schizophrenia, that is also present in many relatives of patients. Animal models of auditory sensory gating indicate that nicotinic cholinergic neurotransmission is a critical neuronal substrate. The aim of this experiment was to determine if the deficit in sensory gating could be reversed by nicotine administration. Nonsmoking relatives of schizophrenics with abnormal sensory gating were selected as subjects for this initial double-blind trial, to avoid effects of psychotropic medications that might complicate trials in schizophrenic patients themselves. Nicotine-containing gum increased P50 sensory gating to near normal levels within 30 min of administration. The effect was transient; the gating of P50 returned to baseline levels within 1 hr. There was no change observed after placebo administration. In one of the subjects, the anticholinesterase inhibitor physostigmine similarly normalized P50 gating. The results are consistent with the hypothesis that nicotinic cholinergic neurotransmission may mediate a familial psychophysiological deficit in schizophrenia.

The role of nicotine and nicotinic mechanisms in neuropsychiatric disease

Cigarette smoking, and by implication nicotine, may be involved as a negative or positive risk factor in some neuropsychiatric disorders and possibly as a treatment in others. Nicotine exposure may be a negative risk factor for the development of Parkinson's disease, but a positive risk factor for the development of tardive dyskinesia. For Alzheimer's disease and Tourette's syndrome, the role of nicotine exposure is equivocal, however, the role of nicotine as a possible therapeutic agent, alone or in combination, remains an intriguing question. For functional psychiatric disorders, the data are suggestive of a link between tobacco use and at least exacerbation of some disorders. While nicotine exposure is unlikely to be critical in the genesis of these disorders, it may complicate the pharmacological therapeutics and long-term prognosis. Further research is needed to examine the actual importance of tobacco use in behavioural disturbances. The relative importance of central nicotinic mechanisms in normal and disordered human cognition and movement is now beginning to be fully explored.

Cigarette smoking and neuroleptic-induced parkinsonism

Several studies have reported an apparent protective effect of cigarette smoking for the risk of idiopathic Parkinson's disease (IPD). These observations are supported by neurochemical studies demonstrating enhancement of central dopaminergic neurotransmission by nicotine. We studied the prevalence and severity of neuroleptic-induced parkinsonism (NIP) in relation to cigarette smoking in a homogeneous sample of 130 psychiatric inpatients receiving long-term neuroleptic treatment. Despite the fact that smokers had significantly higher dosage of neuroleptics during the month prior to evaluation and longer exposure to medication, they presented with significantly less prevalence and severity of NIP than nonsmokers. These findings suggest that the inverse association between smoking and IPD may apply to NIP.

Reduced haloperidol/haloperidol ratios in plasma: polymorphism in Japanese psychiatric patients

We measured plasma concentrations of haloperidol (HAL) and its metabolite, reduced haloperidol (RHAL), by high performance liquid chromatography (HPLC) in 45 Japanese psychiatric patients receiving HAL. Plasma levels of HAL had a highly positive correlation with daily dose per body weight. Plasma RHAL/HAL ratios had also a dose-dependent relationship, but their distribution was nonnormal and a bimodal pattern with an antimode at 0.7 was apparent by probit analysis. There were 8 subjects (18%) with high RHAL/HAL ratios (mean = 1.26, SD = 0.41) and 37 subjects (82%) with low RHAL/HAL ratios (mean = 0.42, SD = 0.13). RHAL/HAL ratios showed little intraindividual variability (+/- 10.6%), while interindividual variability was large. This may suggest that pharmacogenetic factors are involved in the metabolism of HAL and RHAL.

Haloperidol and reduced haloperidol plasma levels in Chinese vs. non-Chinese psychiatric patients

Haloperidol and reduced haloperidol plasma concentrations were measured in age-matched Chinese and non-Chinese patients (n = 32). Steady-state plasma concentrations were obtained 10-12 hours after the bedtime dose. Haloperidol and reduced haloperidol concentrations were measured by liquid chromatography and radioimmunoassay. Haloperidol plasma concentrations did not significantly differ between the populations, but reduced haloperidol levels were 3 times greater in non-Chinese patients than in Chinese patients. The incidence of extrapyramidal side effects was higher in Chinese patients (18 vs. 10), while non-Chinese patients with extrapyramidal symptoms had higher reduced haloperidol plasma levels. Logistic regression analysis revealed that ethnicity and reduced haloperidol/haloperidol ratios were important variables in predicting extrapyramidal symptoms. These results suggest that the metabolism and disposition of haloperidol and reduced haloperidol could differ among ethnic populations.

Hypothesis: a nicotine-dopamine interaction linking smoking with Parkinson's disease and tardive dyskinesia

1. Nicotine, an important pharmacological component of cigarette smoke, is known to have significant effects on central nervous system (CNS) dopaminergic function. Although acute doses of nicotine have been shown to facilitate dopamine release, recent data indicate that chronic nicotine treatment may actually decrease CNS dopamine turnover in the striatum. 2. A number of epidemiological investigations have demonstrated that individuals who are or who have been smokers are less likely to develop idiopathic Parkinson's disease (a disorder involving a deficit in nigrostriatal dopaminergic neurotransmission). In addition, there is preliminary evidence that individuals with tardive dyskinesia (a hyperkinetic movement disorder observed in some cases of chronic neuroleptic treatment and thought by some to be associated with striatal dopamine receptor supersensitivity) are more likely to be smokers. 3. A unitary hypothesis is presented, proposing that smoking in early adult life may decrease CNS catecholamine turnover, thereby protecting against free radical formation from catecholamine oxidation that in turn damages striatal neurons. These individuals are thereby "protected" from the later development of Parkinson's disease. In this hypothetical scheme, individuals who are given neuroleptics and who also are smokers may develop a greater degree of dopamine receptor supersensitivity due to combined receptor blockade by neuroleptics and a decrease in CNS dopamine turnover caused by nicotine, resulting in an increased prevalence of tardive dyskinesia in this group.

A pharmacokinetic study of trifluoperazine in two ethnic populations

The single dose pharmacokinetics of trifluoperazine (5 mg, Stelazine) were investigated in black (n = 25) and white (n = 32) healthy male subjects. Plasma samples were harvested over 24 h and analysed by a GLC-MS method. There were wide intersubject variations in all pharmacokinetic parameters examined, including Cmax, AUC, apparent oral volume of distribution at steady state, and elimination half-life. For each of these parameters the distribution was positively skewed in both blacks and whites and the geometric mean gave a better estimate of central tendency than the corresponding arithmetic mean. In all pharmacokinetic parameters examined there was no significant difference detected between black and white subjects or between smokers and non-smokers.