Ocular permeability of pirenzepine hydrochloride enhanced by methoxy poly(ethylene glycol)-poly(D, L-lactide) block copolymer.

Methoxy poly(ethylene glycol)-poly(D, L-lactide) block copolymer was tested as an ocular permeation enhancer for pirenzepine hydrochloride. The block copolymers with the methoxy poly(ethylene glycol) to poly(D, L-lactide) weight ratio of 80/20, 50/50, 40/60 were synthesized by a ring-opening polymerization procedure. In vitro transcorneal experiments demonstrated that the block copolymer 80/20 significantly enhanced the transcorneal permeation of pirenzepine at the mass ratio of 1/1.4 (pirenzepine hydrochloride/copolymer). Interaction between pirenzepine and copolymer was identified by infrared spectroscopy analysis and dialysis experiments. Ocular pharmacokinetics of pirenzepine/copolymer preparation by in vivo instillation experiments confirmed that block copolymer could enhance the ocular penetration of pirenzepine. Ocular chronic toxicity experiments of block copolymer and pirenzepine/copolymer preparation were studied on rabbits, and no significant toxicity in both groups was observed within 9 months. It could conclude that pirenzepine/copolymer preparation is effective and safe in ocular delivery of pirenzepine.

Tissue distribution of olanzapine in a postmortem case.

Olanzapine is a relatively new antipsychotic drug used in the United States for the treatment of schizophrenia. Since its release in the United States market in 1996, few cases of fatal acute intoxication have been reported in the literature. This article describes the case of a 25-year-old man found dead at home who had been prescribed olanzapine for schizophrenia. This case is unique because of the measurement of olanzapine in brain tissue obtained from seven regions in addition to the commonly collected biologic matrices. Olanzapine was detected and quantitated by basic liquid-liquid extraction followed by dual-column gas chromatographic analysis with nitrogen phosphorus detection. The assay had a limit of detection of 0.05 mg/L and an upper limit of linearity of 2 mg/L. The presence of olanzapine was confirmed by gas chromatography-mass spectrometry by use of electron impact ionization. The concentrations of olanzapine measured in this case were as follows (mg/L or mg/kg): 0.40 (heart blood), 0.27 (carotid blood), 0.35 (urine), 0.61 (liver), negative (cerebrospinal fluid), 0.33 mg in 50 ml (gastric contents). In the brain, the following distribution of olanzapine was determined (mg/kg): negative (cerebellum), 0.22 (hippocampus), 0.86 (midbrain), 0.16 (amygdala), 0.39 (caudate/putamen), 0.17 (left frontal cortex), and 0.37 (right frontal cortex). The cause of death was determined to be acute intoxication by olanzapine, and the manner of death was accidental.

Quinpirole, 8-OH-DPAT and ketanserin modulate catalepsy induced by high doses of atypical antipsychotics.

The effect of the selective dopamine D2 receptor agonist quinpirole, the selective 5-HT1A receptor agonist 8-OH-DPAT and the selective 5-HT2A receptor antagonist ketanserin on catalepsy induced by atypical antipsychotics clozapine, risperidone, olanzapine and sertindole at higher doses was studied in rats. Haloperidol (0.5, 1 and 2 mg/kg), clozapine (50 and 75 mg/kg) and olanzapine (15 and 30 mg/kg) produced catalepsy dose-dependently while sertindole at doses up to 40 mg/kg failed to produce catalepsy in rats. However, sertindole (15, 30 and 45 mg/kg) produced a cataleptic effect in mice in a dose-dependent manner. At a high dose (5 mg/kg), risperidone produced catalepsy in rats. Quinpirole (0.05 and 0.1 mg/kg) reversed the cataleptic effect of haloperidol (2 mg/kg), risperidone (5 mg/kg), olanzapine (30 mg/kg) and sertindole (45 mg/kg). Quinpirole (0.05 and 0.1 mg/kg) reversed clozapine (75 mg/kg)-induced catalepsy. 8-OH-DPAT (0.15 and 0.3 mg/kg) dose-dependently reversed catalepsy induced by haloperidol (2 mg/kg) and risperidone (5 mg/kg) without affecting the cataleptic effect of olanzapine. However, the higher dose (0.45 mg/kg) of 8-OH-DPAT reversed it significantly. 8-OH-DPAT (0.3 mg/kg) reversed clozapine (75 mg/kg)-induced catalepsy. 8-OH-DPAT (0.15, 0.3 and 0.45 mg/kg) failed to reverse sertindole-induced catalepsy. Ketanserin (0.75 and 1.5 mg/kg) completely reversed catalepsy induced by haloperidol (2 mg/kg) and risperidone (5 mg/kg). Ketanserin (0.75 and 1.5 mg/kg) dose-dependently reversed olanzapine (30 mg/kg) and sertindole (45 mg/kg)-induced catalepsy without any effect on clozapine (75 mg/kg)-induced catalepsy. A higher dose (3 mg/kg) of ketanserin reversed clozapine-induced catalepsy. The present study suggests that atypical antipsychotics show fewer extrapyramidal symptoms (EPS) due to greater modulation of the serotonergic system. Therefore, an antipsychotic with dopamine D2/5-HT2A antagonistic action and 5-HT1A agonistic action may prove to be superior to the existing antipsychotics.

Chronic olanzapine or sertindole treatment results in reduced oral chewing movements in rats compared to haloperidol.

Chronic haloperidol treatment typically produces late-onset, purposeless oral chewing movements in laboratory rats with a prevalence of 40 to 60%. Chronic clozapine does not produce these movements. Based on the phenomenologic and pharmacologic similarities between these rat chewing movements and human tardive dyskinesia (TD), the animal movements are often used as a model of tardive dyskinesia (TD). Here we report results of the association of oral chewing movements in rats with chronic administration of two new antipsychotic drugs, olanzapine and sertindole. Because each of these antipsychotic drugs has a very low incidence of acute Parkinsonism in human studies, they are candidates for showing a low tardive dyskinesia risk. Neither new drug produced a significant incidence of haloperidol-like chewing in rats, nor did movement ratings after their chronic administration differ from placebo; whereas, haloperidol produced a 60% prevalence of purposeless chewing and a prevalence significantly increased from placebo. This low rate of oral dyskinesias in rats is consistent with several of the preclinical characteristics of the drugs and correlates with their low acute motor side effects in clinical trials. We propose, although have not yet tested in humans, that these animal results will predict low TD liability of these drugs.

A comparison of the oxidation of clozapine and olanzapine to reactive metabolites and the toxicity of these metabolites to human leukocytes.

Olanzapine was shown to be oxidized to a reactive intermediate by HOCl, which is the major oxidant produced by activated neutrophils. A mass spectrum obtained using a flow system in which the reactants were fed into a mixing chamber and the products flowed directly into a mass spectrometer revealed a reactive intermediate at m/z 311. This is 2 mass units less than the protonated molecular ion of parent olanzapine and suggests that the reactive intermediate is a nitrenium ion. The reactive intermediate could be trapped with glutathione or N-acetylcysteine to produce two conjugates. These data are analogous to results we reported previously with the structurally related atypical antipsychotic agent clozapine. However, the clozapine and olanzapine reactive metabolites showed differences in their ability to cause toxicity to human neutrophils. Toxicity to neutrophils was observed only at high concentrations of clozapine (>50 microM) when HOCl was used to generate reactive metabolite. In contrast, concentration-dependent toxicity (p < 0.05) was observed when neutrophils were incubated with clozapine (0-20 microM) and H2O2 to generate clozapine reactive metabolite. No toxicity was observed with clozapine alone (at concentrations of > 50 microM). Similar results were observed in monocytes and HL-60 cells. Olanzapine reactive metabolite only seemed to cause slight toxicity at the highest concentrations tested (20 microM), even when the reactive metabolite was generated using H2O2. Neutrophils from two patients with a history of clozapine-induced agranulocytosis seemed to be more sensitive to the toxic effects of the clozapine reactive metabolite; however, the numbers are too small to draw any definite conclusions.

Dysfunction of muscarinic M2 receptors after the early allergic reaction: possible contribution to bronchial hyperresponsiveness in allergic guinea-pigs.

1. Using a guinea-pig model of allergic asthma, in which the animals display early (0-5 h) and late phase (8-23 h after antigen challenge) bronchoconstrictor reactions, the function of prejunctional inhibitory M2 and postjunctional M3 receptors in isolated tracheal preparations have been investigated. In addition, cardiac M2 receptor function in vitro and bronchial responsiveness to histamine in vivo were evaluated. 2. Sensitivity to inhaled histamine was increased 3.1 fold and 1.6 fold after the early and late allergic reactions (i.e. at 5 h and 23 h after a single ovalbumin challenge), respectively. At 23 h after the last of four allergen challenges, executed on four consecutive days, bronchial hyperresponsiveness to histamine was diminished to 1.3 fold. 3. After the early response, there was no change in cardiac muscarinic M2 receptor function, since in left atria pD2 (-log EC50) and Emax values of pilocarpine and pKB values of AQ-RA 741, a selective M2 receptor antagonist, were not significantly different from controls (unchallenged sensitized animals), and this also applied to methacholine pD2 values for muscarinic M3 receptors in tracheal smooth muscle. 4. Prejunctional inhibitory muscarinic M2 autoreceptors in airway smooth muscle were markedly dysfunctional after the early allergic response, since potentiation of electrically evoked twitch contractions of tracheal preparations by low concentrations of the M2-selective muscarinic receptor antagonists, gallamine, methoctramine, AQ-RA 741 and AF-DX 116, which is the result of M2 receptor blockade, was clearly and significantly diminished compared to controls. However, after the late response, both in single and repeatedly challenged animals, twitch potentiation was not significantly different from and similar to controls, indicating restoration of M2 receptor function during the late allergic reaction.5. It is concluded that dysfunction of muscarinic M2 autoreceptors in the airways of sensitized and challenged guinea-pigs is already present after the early allergic reaction, and that it has recovered after the late response. Since histamine-induced bronchoconstriction involves vagal pathways, the present results suggest that bronchial hyperresponsiveness to histamine is partly due to M2 auto receptor dysfunction, leading to increased release of acetylcholine.