The bioavailability and pharmacokinetics of subcutaneous, nebulized and oral morphine-6-glucuronide

AIMS

Morphine-6-glucuronide (M6G), one of the active metabolites of morphine, has attracted considerable interest as a potent opioid analgesic with an apparently superior therapeutic index. To date studies have used the intravenous route, which is generally unacceptable in the treatment of cancer related pain. The aim of this study was to define the pharmacokinetics, toxicity and cardio-respiratory effects of three alternative routes of administration of M6G.

METHODS

Ten healthy volunteers participated in an open randomized study. Subjects received M6G 2 mg as an intravenous bolus, 20 mg orally, 2 mg subcutaneously and 4 mg by the nebulized route. Pulse, blood pressure, respiratory rate and peak flow rate were monitored and subjective toxicity recorded on rating and visual analogue scales.

RESULTS

After i.v. M6G the mean (+/- s.d.) AUC(0,infinity) standardized to a dose of 1 mg was 223 +/- 57 nmol l(-1) h, mean elimination half-life was 1.7 +/- 0.7 h and the mean clearance was 157 +/- 46 ml min(-1). These parameters were virtually identical after subcutaneous administration which had a bioavailability (F(0,infinity)) of 102 +/- 35% (90% CI 82, 117%) and t(max) of 0.5 +/- 0.2 h. The mean bioavailability of nebulized M6G was 6 +/- 2% (90% CI 4, 7%) with a t(max) of 1.2 +/- 0.8 h. Following oral M6G two plasma M6G peaks were seen in 7 of the 10 subjects, the first with a t(max) of 3.1 (+/- 0.9) h. The second peak had a t(max) of 13.4 (+/-5.0) h, started approximately 4 h after dosing, and was associated with the detection of plasma M3G and morphine, suggesting that M6G was significantly hydrolysed in the gut to morphine, which was then glucuronidated following absorption. Although the overall mean bioavailability was 11 +/- 3% (90% CI 9, 12%), confining the analysis to data from the first peak suggested a bioavailability of directly absorbed M6G of only 4 +/- 4%. Apart from a characteristic dysphoria following intravenous and subcutaneous M6G, there was no significant toxicity.

CONCLUSIONS

With the minimal toxicity reported in this and previous studies, subcutaneous infusion of M6G may potentially provide clinically useful analgesia for advanced cancer pain. Nebulized M6G is not significantly absorbed via the lungs, and if opiates are shown to have a local effect in the lung, reducing the sensation of breathlessness, then nebulized administration is likely to minimize systemic effects. Oral M6G has poor bioavailability, but is significantly hydrolysed in the gut to morphine, which is subsequently glucuronidated following absorption. This circuitous route accounts for the majority of systemically available M6G after oral administration.

Restlessness in suboccipital muscles as a manifestation of akathisia

Antipsychotic-induced akathisia is primarily manifested as restlessness, particularly expressed in the legs. Consequently, rating scales and the research criteria of DSM-IV regard restlessness in the legs as the major sign of akathisia, although it has been suggested that such restlessness may occur in other areas of the body. A case of antipsychotic-induced akathisia is reported where the region of inner restlessness (the subjective component) was identified in posterior cervical muscles. The patient was initially suspected to be experiencing somatic delusions and the dose of antipsychotic medication was increased. This did not improve the symptoms, and upon careful questioning about his head discomfort, the patient acknowledged that he felt an inner restlessness in the suboccipital muscles. The restlessness ceased with intramuscular biperiden and subsequent discontinuation of antipsychotic medication. This case suggests that subjective restlessness may occur in muscle groups that are not usually associated with akathisia. Thus, this report may assist clinicians in the diagnosis of akathisia that could be overlooked or misdiagnosed as somatic delusions or the worsening of the patient's psychosis.

Clomipramine augmentation in treatment-resistant depression

In depression that is resistant to tricyclic antidepressant (TCA) therapy, the substitution of a selective serotonin re-uptake inhibitor (SSRI), clomipramine, or a monoamine oxidase (MAO) inhibitor has been recommended. However, adding an additional antidepressant medication from a different drug class may produce even more rapid efficacy. In this regard, the combination of a MAO inhibitor or a SSRI plus a TCA has been shown to be of value in treatment-resistant depression (TRD). In this report, we examined the efficacy of clomipramine augmentation in 20 patients who failed to respond to either a MAO inhibitor or fluoxetine therapy for at least a 6-week period, and compared this to a third group given MAO inhibitor plus a conventional TCA. Two out of 9 (22%) MAO inhibitor/clomipramine patients and 4 out of 11 (36%) fluoxetine/clomipramine patients improved (Fisher's Exact test, P = ns), compared to 3 out of 7 (43%) patients taking MAO inhibitor/TCA (P = ns). However, the MAO inhibitor/clomipramine group experienced significantly more adverse events which necessitated stopping treatment (56%) when compared to the fluoxetine/clomipramine (9%) and compared to the MAO inhibitor/TCA group (0%) (chi 2 = 8.9, df = 2, P < 0.05). These adverse events included several cases of serotonin syndrome of mild to moderate severity. These observations indicate that clomipramine augmentation of a failed MAO inhibitor trial is of marginal efficacy (compared to augmentation with a conventional TCA) and should be employed with extreme caution.

Fluoxetine and concomitant centrally acting medication use during clinical trials of depression: the absence of an effect related to agitation and suicidal behavior

Concomitant use of psychoactive medications is a common practice in most clinical trials of antidepressant medications. However, the relative therapeutic impact of such use on trial results has not been the subject of much attention. We conducted a meta-analysis to determine whether concomitant use of psychoactive medications confounded the efficacy or safety results of a series of fluoxetine trials. Data were evaluated from 25 randomized, double-blind clinical trials comparing fluoxetine with placebo or a tricyclic antidepressant (TCA) in 4,016 patients with major depression. We compared incidence rates of concomitant use of anxiolytics, sedatives, and antipsychotics between treatments. In addition, we compared the change in total score for the 21-Item Hamilton Depression Rating Scale (HAMD21): incidence rates of any worsening, emergence, or improvement in psychomotor agitation; and incidence of suicidal acts and any worsening, emergence, or improvement in suicidal ideation between treatment groups among patients taking/not taking a sedative. Anxiolytic and antipsychotic drug use was uncommon (8.3% and 0.9% overall use, respectively) and did not substantially increase over time. Sedative drugs were used most often (29.6% overall), but only 29.8% of the fluoxetine-treated patients took one or more doses. Regarding efficacy, fluoxetine was superior to placebo in decreasing HAMD21 total scores among patients taking/not taking sedatives. Effects on safety were assessed by examining agitation and suicidal ideation. Use of sedatives did not affect the change in the HAMD agitation score; scores were similar in patients receiving fluoxetine, placebo, and TCAs. In all treatment groups, anxiolytic use tended to increase as the HAMD anxiety score increased. Fluoxetine was superior to placebo in treating suicidal ideation, and the concomitant use of sedatives did not influence this effect. Overall, concomitant use of psychotropic medications in the fluoxetine depression clinical trials was uncommon. Our meta-analysis demonstrated that the clinical efficacy and safety of fluoxetine were not confounded by the concomitant use of medications.

New antipsychotic medications: more than old wine and new bottles

Four new antipsychotic medications--clozapine, risperidone, olanzapine, and quetiapine--have been introduced in the United States during the past decade. These new medications now account for the majority of antipsychotic prescriptions. The author reviews specific issues related to the use of traditional antipsychotic medications and then highlights the emerging clinical research data regarding the new medications, which have all been shown to be efficacious in the treatment of schizophrenia. Clinical research data indicate that they are also more useful for a broader array of symptoms associated with schizophrenia than traditional compounds. Furthermore, movement disorder side effects are substantially decreased--a property that leads to higher acceptability. Surprisingly, there has been little relationship between the pivotal trials designed for FDA approval and current dosing strategies in broader clinical settings. These dosing issues are described. New uses, including treatment of mood disorders and conduct disorder, are also discussed. These medicines offer substantial hope for improved treatment of schizophrenia.

Comparative efficacy of olanzapine and haloperidol for patients with treatment-resistant schizophrenia

BACKGROUND

There is relatively little information regarding the efficacy of newer atypical antipsychotic drugs for patients with schizophrenia who are treatment-resistant to neuroleptic agents. Several lines of evidence suggest that a clinical trial of olanzapine in this population is warranted.

METHODS

A subpopulation of patients (n = 526) meeting treatment-resistant criteria selected from a large, prospective, double-blind, 6-week study assessing the efficacy and safety of olanzapine and haloperidol were examined. Both last-observation-carried-forward (LOCF) and completers (observed cases) analyses were conducted.

RESULTS

Olanzapine demonstrated significantly greater mean improvement from baseline in Positive and Negative Syndrome Scale (PANSS) negative symptoms, comorbid depressive symptoms assessed by the Montgomery-Asberg Depression Rating Scale, akathisia as measured by Barnes Akathisia Scale, and extrapyramidal symptoms as measured by Simpson-Angus Extrapyramidal Rating Scale with both LOCF and completers analyses. In addition, olanzapine was significantly superior to haloperidol for Brief Psychiatric Rating Scale total (p = .006), PANSS total (p = .005), and PANSS positive symptoms (p = .017) in completers of the 6-week study. Significantly greater response rates were observed in olanzapine-treated (47%) than haloperidol-treated (35%) patients in the LOCF analysis (p = .008), but significance was not reached in the completers analysis (p = .093). Mean doses (+/- SD) of olanzapine and haloperidol were 11.1 +/- 3.4 mg/day and 10.0 +/- 3.6 mg/day, respectively.

CONCLUSIONS

Olanzapine was superior to haloperidol for key symptom domains and parkinsonian side effects. Implications of these data for the therapeutics of this severely ill subgroup are discussed.

[Recent progress in akathisia]

Neuroleptic-induced akathisia should be definitely diagnosed as acute, tardive, withdrawal, and chronic. The diagnostic assessment must be identified from the subjective report and objective features. Various assessments of measuring akathisia can be clinically used by instrumental methods and rating scales. The pharmacological basis of neuroleptic-induced akathisia is the inhibition of the dopamine receptors in the brain. The pathogenesis of neuroleptic-induced akathisia may involve GABAergic hypoactivity, noradrenergic hyperactivity, and serotonergic dysfunction in CNS. Iron deficiency and hyperglycemia may be risk factors of neuroleptic induced akathisia in relation to the dopamine function in the brain. Neurological disorders may be associated with the development of a syndrome resembling drug-induced akathisia. The lesion of the thalamic nuclei would originally produce the syndrome. The difference between acute and tardive akathisia on the strategy of the drug treatment should be sufficiently comprehended. In particular, the long-term use of anticholinergic drugs and benzodiazepines should not be prevailed.

Effects of dopaminergic combination therapy for frontal lobe dysfunction in traumatic brain injury rehabilitation

Traumatic brain injury poses significant and diverse challenges to rehabilitation efforts. Neurobehavioural deficits represent a particularly difficult barrier to rehabilitative progress and societal reintegration. Early studies have identified dopaminergic drugs such as amantadine, bromocriptine and sinemet as potentially assistive in countering these deficits. To date, side effect profiles have been relatively benign, noted most frequently in small-scale case trials. The case of a 40-year-old patient with bilateral frontal traumatic brain injuries, and previous arteriovenous malformation (AVM) bleed with significant ataxia, dysarthria and neurobehavioural deficits is presented. This long range study demonstrates, through multiple varied dosing schedules, a trade off between the benefits and side effects of dopaminergic therapy, with implications for a larger brain injury population.

Tardive blepharospasm

I report on five patients with tardive blepharospasm seen in a movement disorders clinic, out of 25 tardive dystonia patients. They were young (aged 25-50 yrs); four were men and three had a schizophrenic disorder. The onset was gradual while on maintenance neuroleptics in four and on withdrawal in the fifth. There were no significant antecedent events precipitating the disorder. The disorder was bilateral but asymmetric in two cases. Dyskinetic blinking was often an initial feature and tended to persist after the resolution of the blepharospasm. Orolingual dyskinesia was present in one case and tardive akathisia in two other cases. The symptoms fluctuated in severity with a number of exacerbating and relieving factors. Reduction of neuroleptic dose led to improvement with complete reversal in one of two patients who could be withdrawn off neuroleptic medication. These reports suggest that TB, although uncommon, can be a disabling disorder that may improve considerably with the cessation or dose reduction of the neuroleptic drugs. Its treatment and longitudinal course should be further examined.

Side reaction caused by the perfluorocarbon emulsions in intravenous infusion to experimental animals

The perfluorocarbon (PFC) emulsions are infusion gas-transporting media and are usually called the artificial blood. However anaphylactoid reaction were observed during intravenous infusion of PFC emulsions. The cause of side reactions is the activation of the complement system. An indirect sign of the intravascular activation of the complement is the neutropenic effect in the peripheric blood. Taking into consideration the phenomen, the method of evaluation of anaphylactoid reaction caused by PFC emulsions has been elaborated using the neutropenic index. We evaluated the biocompatibility of 26 PFC emulsions of different composition in intravenous infusion to rabbits using this index. Emulsions evoked reactions of different extent. Some emulsions did not cause the neutropenic effect at all. Results of this work allow to reach conclusion, that influence of PFC emulsions on the complement system is explained not only by emulsifying agent proxanol: the stability of emulsions in the vascular bed and in the period of storage in frozen state is of great importance as well.

Effect of single doses of S-salbutamol, R-salbutamol, racemic salbutamol, and placebo on the airway response to methacholine

BACKGROUND

Commercially available salbutamol is a racemic mixture consisting of equal amounts of the two enantiomers, R-salbutamol and S-salbutamol, felt to be active and inert, respectively.

METHODS

A double blind, randomised, four way, crossover study was performed in 12 well controlled asthmatic subjects (forced expiratory volume in one second (FEV1) > 70% predicted, no beta 2 agonists for > or = 4 weeks). Subjects were studied on four days at intervals of 48 hours to seven days. FEV1 was assessed before and both FEV1 and methacholine PC20 were measured 20 and 180 minutes after a single dose of nebulised racemic salbutamol 2.5 mg, R-salbutamol 1.25 mg, S-salbutamol 1.25 mg, and placebo.

RESULTS

Equivalent bronchodilation was seen for both R-salbutamol and racemic salbutamol (mean (SE) 12.4 (3.1)% and 12.0 (3.0)%, respectively, at 20 minutes and 5.9 (2.9)% and 5.2 (2.2)% at 180 minutes). The increase in FEV1 of 5.2 (0.9)% at 20 minutes and the decline in FEV1 of 2.9 (2.1)% at 180 minutes after S-salbutamol were not significantly different from the placebo response. Compared with placebo the methacholine PC20 after R-salbutamol and racemic salbutamol improved by 3.3 (95% CI 2.5 to 4.1) and 3.4 (95% CI 2.6 to 4.2) doubling doses, respectively, at 20 minutes and 1.2 (95% CI 0.6 to 1.8) and 1.0 (95% CI 0.2 to 1.8) doubling doses at 180 minutes. S-salbutamol resulted in an improvement of 0.9 (95% CI 0.3 to 1.5) doubling doses at 20 minutes and no change at 180 minutes. Restlessness (n = 11) and increased pulse were seen 20 minutes after racemic and R-salbutamol but not S-salbutamol or placebo, and not at 180 minutes. There were no other adverse events.

CONCLUSION

A single dose of 1.25 mg nebulised R-salbutamol produced equivalent bronchoprotection, bronchodilation, restlessness, and tachycardia as did 2.5 mg of racemic salbutamol. S-salbutamol 1.25 mg had a weak bronchoprotective effect; this could be because of a small amount of contamination with R-salbutamol or because S-salbutamol is an intrinsically weak beta 2 receptor stimulant.

[Four-week intravenous toxicity study of montirelin hydrate (NS-3) in dogs followed by 4-week recovery test]

A repeated dose toxicity study of montirelin hydrate (NS-3), a new drug for the treatment of disturbance of consciousness, was conducted in beagle dogs. The dogs were given the drug intravenously for 4 weeks at doses of 0 (control), 0.0002, 0.002, 0.02, 0.2, 2 and 20 mg/kg in males and 0, 0.2, 2 and 20 mg/kg in females. After discontinuation of the treatment, a 4-week recovery test was also conducted in the 0 and 20 mg/kg groups. No deaths related to the treatment were observed. There were no changes in body weight gain, and food and water consumptions. Nasal discharge was seen in all dose groups. Salivation, emesis and hypoactivity were observed in the 0.2 mg/kg group and over. Licking chops were seen in the 2 and 20 mg/kg groups. Trembling and agitated/restless behavior were seen in the 20 mg/kg group. Electrocardiographic examination revealed elevated heart rate in the 0.2 mg/kg group and over. Ophthalmoscopic and hematologic examinations, and urinalysis failed to show any abnormalities attributable to the treatment. Blood chemical examination disclosed increases in T3 level in the 2 and 20 mg/kg groups of males and in T4 level in the 0.2 mg/kg group and over of males. There were no pathological findings attributable to the treatment. The changes mentioned above were satisfactorily reversible. The nasal discharge seen in the 0.02 mg/kg group and below was considered to be of no toxicological significance. These results show that the NOAEL of montirelin hydrate is 0.02 mg/kg for 4-week repeated dose toxicity in dogs.

Intrathecal prostaglandin E1 produces a long-lasting allodynic state

The existence of prostaglandin (PG) receptors in the spinal cord has been demonstrated, but their role in sensory processing is not yet well defined. PGE1 is widely used clinically as a vasodilator. The present study was designed to investigate the effects of intrathecally administered PGE1 on the transmission of different types to sensory information, including that associated with noxious somatic, noxious visceral, and non-noxious somatic stimulation. The tail-flick (TF) test was employed to measure responses to noxious somatic stimuli, and the colorectal distension test was used to examine responses to noxious visceral stimuli. Withdrawal response to mechanical pressure produced by Semmes-Weinstein mono-filaments (SWMs) was measured as an assessment of sensitivity to non-noxious mechanical somatic stimulation. TF latencies and colorectal distension thresholds decreased for a short time (10-20 min) following the intrathecal (i.t.) administration of both 100 ng or 500 ng of PGE1. In sharp contrast to these short duration effects, there was a long-lasting increase in agitation scores (allodynia) produced by 3 different intensities of SWMs (0.217, 0.745 and 2.35 g) after administration of PGE1. The changes in agitation scores to SWMs were dependent on the dose of PGE1 and the intensity of stimulation. This increase of agitation score was seen when PGE1 was administered through the i.t. catheter or by direct i.t. puncture and the increase lasted for at least 2 days after drug administration. Intrathecal administration of saline, however, did not produce any changes in TF latencies, colorectal distension thresholds, or agitation scores produced by SWMs. No significant histological difference was seen between spinal cords exposed to 500 ng PGE1 and saline 48 h after drug administration. These results demonstrate that PGE1 may trigger a hypersensitive (allodynic and/or hyperalgesic) state in sensory processing pathways at the spinal level. They also indicate that long-lasting changes in processing of non-noxious, but not noxious, information produced by PGE1 continues after the disappearance of the direct action of PGE1.

[Problems of epidural droperidol administration]

We describe three cases of extrapyramidal reactions apparently caused by epidural administration of droperidol. These patients suffered from chronic pain and was treated with epidural lidocaine and droperidol. Two patients received continuous administration of droperidol, and experienced acute dystonia and another after a single dose, developed akathisia. Adverse reactions occurred at 15, 20 and 24 hours after the administration of droperidol. The first patient received droperidol 6 mg, the second 8.5 mg and the third 5 mg. We consider that extrapyramidal reactions are due to overdoses because the patients who had been given less than 2.5 mg of droperidol a day, showed no adverse reaction. Although we use higher doses with NLA or for management of fever than with epidural administration of droperidol, we seldom encounter cases of side effects with droperidol. Epidurally administrated droperidol spreads rostral within the neuraxis and causes delayed extrapyramidal reactions as epidural morphine develops delayed respiratory depression. We must be careful in caring patients suffering from chronic pain with continuous epidural administration of droperidol.

Adverse effects of antipsychotic drugs

Since the introduction of chlorpromazine in the 1950s, neuroleptic medications have been the mainstay of treatment of schizophrenia and other psychotic disorders. These medications do not always lead to complete remission of symptoms but they have allowed many patients to lead more productive and satisfying lives away from the restrictions of chronic hospitalisation. However, neuroleptics are associated with a number of adverse effects that can compromise their effectiveness. Extrapyramidal adverse effects include acute dystonic reactions, neuroleptic-induced Parkinsonism and akathisia. They can often be treated with neuroleptic dose reduction, addition of anticholinergic or beta-blocking agents, or medication change. Later-onset movement disorders such as tardive dyskinesia or dystonia require careful evaluation and may be treated with dose reduction or change of neuroleptic to an atypical agent. Potentially fatal reactions such as agranulocytosis and neuroleptic malignant syndrome can rarely occur and often require significant medical intervention. Clozapine offers some advantages over 'typical' neuroleptics but has a unique adverse effect profile which includes agranulocytosis.

Effects of prior cocaine exposure on subsequent neuronal responsiveness

In vivo electrophysiological experiments were conducted to examine the responses of single, spontaneously-active neostriatal neurons to repeated cocaine exposure. The second of two administrations in a 30 min interval, attenuated the magnitude and duration of cocaine-induced depression in discharge rate, and enhanced the same variables for cocaine-evoked excitation. These findings indicate that the responsiveness of striatal neurons to cocaine may vary predictably as a function of previous exposure.

Cigarette smoking in schizophrenia: relationship to psychopathology and medication side effects

OBJECTIVE

The authors' goal was to study the relationship between smoking status and clinical characteristics in schizophrenic patients.

METHOD

Seventy-eight schizophrenic outpatients were assessed by a single rater using the Brief Psychiatric Rating Scale (BPRS), the Abnormal Involuntary Movement Scale, and the Simpson-Angus Scale for extrapyramidal symptoms. Current smokers (N = 58) were compared with nonsmokers (N = 20) on clinical variables by independent t tests and chi-square tests. Differences in outcome variables were tested by multiple analysis of covariance (ANCOVA) with smoking status and gender as factors and age, neuroleptic dose, and caffeine consumption as covariates.

RESULTS

Seventy-four percent of patients were current smokers and reported a mean of 19 cigarettes smoked per day. Compared to nonsmokers, current smokers were significantly more likely to be men, to be younger, and to have had an earlier age at onset and a greater number of previous hospitalizations. Current smokers and nonsmokers received mean neuroleptic doses of 1160 and 542 mg/day (chlorpromazine equivalents); the difference was significant. Current smokers also displayed significantly less parkinsonism and more akathisia and had higher total scores on the BPRS. Overall multiple ANCOVA demonstrated a significant main effect for smoking status but not gender or the interaction between gender and smoking status. Univariate ANCOVAs demonstrated a significant main effect of smoking status only for the Simpson-Angus Scale score.

CONCLUSIONS

Cigarette smokers receive significantly higher neuroleptic doses, in part because of a smoking-induced increase in neuroleptic metabolism. Smoking is also associated with significant reduction in levels of parkinsonism. Smoking status is a significant factor that should be considered in assessment of neuroleptic dose requirements and neuroleptic side effects.