The effects of concomitant phenytoin administration on the steady-state pharmacokinetics of quetiapine.

Quetiapine fumarate ('Seroquel') is a newly introduced atypical antipsychotic with demonstrated efficacy in the treatment of positive and negative symptoms of schizophrenia. It is extensively metabolized, predominantly by cytochrome P450 3A4. Therefore, concurrent administration of drugs that induce or inhibit this enzyme may affect quetiapine pharmacokinetics. This study demonstrated that the potent cytochrome P450 enzyme-inducer phenytoin did indeed have a marked effect on the metabolism of quetiapine, resulting in a 5-fold increase in clearance when administered concomitantly to patients with DSM-IV-diagnosed schizophrenia, schizoaffective disorder, or bipolar disorder. These results indicate that dosage adjustment of quetiapine may be necessary when the two drugs are given concurrently and that caution may be required when administering other drugs that inhibit or induce cytochromes, particularly P450 3A4.

Single-dose pharmacokinetics of quetiapine in subjects with renal or hepatic impairment.

1. The atypical antipsychotic quetiapine ('Seroquel') provides equivalent efficacy to the typical antipsychotics chlorpromazine and haloperidol in the short-term treatment of schizophrenia. Moreover, the incidence of extrapyramidal symptoms associated with quetiapine treatment is equivalent to that observed with placebo treatment, which may lead to increased patient compliance with quetiapine compared with typical antipsychotics. 2. This report presents the results from two small studies aimed at determining the pharmacokinetics of quetiapine in nonpsychotic subjects with renal or hepatic impairment. Equal numbers of impaired subjects and healthy control subjects were administered a single, 25 mg dose of quetiapine, and plasma concentrations were determined up to 48 hr after dosing. 3. No clinically significant differences were found when the pharmacokinetic parameters for subjects with renal or hepatic impairment were compared with those for healthy control subjects. The results indicate that dosage adjustment of quetiapine may be unnecessary in psychotic patients with decreased renal function. 4. In subjects with hepatic impairment related to alcoholic cirrhosis, the results suggest that no change is needed in the recommended quetiapine starting dose (25 mg). However, because of a noted inter-subject variability in the clearance of quetiapine in the cirrhotic group, it is recommended that dose escalation be performed with caution in patients with hepatic impairment. 5. The single dose of quetiapine 25 mg generally was well tolerated in nonpsychotic subjects in good health or with either renal or hepatic impairments. Quetiapine also had no effect on the endogenous creatinine clearance of renally impaired or healthy control subjects.

Pharmacokinetics, tolerability, and clinical effectiveness of quetiapine fumarate: an open-label trial in adolescents with psychotic disorders.

BACKGROUND: This is the first investigation of the pharmacokinetics, tolerability, and efficacy of quetiapine fumarate in adolescents with chronic or intermittent psychotic disorders. METHOD: Ten patients with DSM-IV chronic or intermittent psychotic disorders (ages 12.3 through 15.9 years) participated in an open-label, rising-dose trial and received oral doses of quetiapine twice daily (b.i.d.), starting at 25 mg b.i.d. and reaching 400 mg b.i.d. by day 20. The trial ended on day 23. Key assessments were pharmacokinetic analysis of plasma quetiapine concentrations and neurologic, safety, and efficacy evaluations. RESULTS: No statistically significant differences were observed between 100-mg b.i.d. and 400-mg b.i.d. quetiapine regimens for total body clearance, dose-normalized area under the plasma concentration-time curve, or dose-normalized premorning- or postmorning-dose trough plasma values obtained under steady-state conditions after multiple-dose regimens. No unexpected side effects occurred with quetiapine therapy, and no statistically significant changes from baseline were observed for the UKU Side Effect Rating Scale items that were rated. No serious adverse events or clinically important changes in hematology or clinical chemistry variables were reported. The most common adverse events were postural tachycardia and insomnia. Extrapyramidal side effects improved, as evidenced by significant (p < .05) decreases from baseline to endpoint in the mean Simpson-Angus Scale total scores and Barnes Akathisia Scale scores. Quetiapine improved positive and negative symptoms, as shown by significant (p < .05) decreases from baseline to endpoint in the mean Brief Psychiatric Rating Scale total score, the Clinical Global Impressions-Severity of Illness scale, and the Modified Scale for the Assessment of Negative Symptoms summary score. CONCLUSION: Quetiapine pharmacokinetics were dose proportional in adolescents and were similar to those previously reported for adults. Quetiapine was well tolerated and effective in the small number of adolescents studied.

Long-term safety and efficacy of zafirlukast in the treatment of asthma: interim results of an open-label extension trial.

BACKGROUND: Current guidelines recommend anti-leukotriene agents as alternative treatments for mild persistent asthma; however, information on their long-term safety and efficacy is needed. OBJECTIVE: To evaluate long-term safety and efficacy of and compliance with oral zafirlukast (Z; 20 mg BID) during the first 39 weeks of ongoing, multicenter, open-label extension (OLE) of a previously reported 13-week, randomized (2:1), double-blind (DB), placebo (P)-controlled trial in mild-to-moderate asthmatic patients treated previously with beta2-agonists alone. METHODS: Patients (12 to 76 years; FEV1 > or = 55% predicted) elected to enter OLE after completing the DB trial. Safety evaluated by adverse events (AEs), laboratory tests, and physical and electrocardiographic examinations. Efficacy assessed by spirometry measurements [FEV1, FEV1 % predicted, personal-best (post-bronchodilator) FEV1] and treatment failure rates. Compliance was calculated as percentage of treatment dispensed. After a visit at OLE week 3 (week 16), patients had visits every 12 weeks. RESULTS: A total of 443 patients (nz-->z = 310, np-->z = 133) entered the OLE. Results through the OLE period showed that 80% of patients overall reported AEs. Of patients randomized to Z and P during DB period, 68% and 67%, respectively, reported AEs during quarter I (Q1); percentage of Z-treated patients reporting AEs during the OLE ranged from 66% (Q2) to 44% (Q4). Review by quarters showed occurrence of AEs in Z-treated groups (Q2-4) was similar to that in P group (Q1). Compared with baseline (week 0), modest yet significant improvements (P < or = .02) in all spirometry measurements were noted in Z --> Z and P --> Z groups at OLE week 3, with sustained effects noted during OLE period. Treatment failure rates during OLE ranged from 7.2% (Q2) to 3.3% (Q4). Mean compliance ranged from 98% (OLE week 3) to 95% (OLE week 39). CONCLUSIONS: Long-term treatment with zafirlukast was safe and well tolerated in asthmatic patients. Sustained efficacy and asthma control and good compliance were observed over extended treatment period. Results demonstrate long-term safety and effectiveness of and compliance with this anti-leukotriene agent.

Pharmacokinetics of meropenem in patients with liver disease.

Eight subjects with chronic stable alcoholic cirrhosis and eight matched controls with normal liver function were given an initial 30-minute intravenous infusion of 1 g of meropenem; beginning 24 hours later, they received five additional 1-g doses at 6-hour intervals. No statistically significant differences were found between the first dose and steady state or between groups for any plasma pharmacokinetic parameters-including the highest observed plasma concentrations, plasma concentrations at 6 hours after dosing (C6h), terminal half-life, area under the plasma concentration-time curve (AUC), area under the first moment of the curve, plasma clearance, steady-state volume of distribution, and accumulation ratios-on the basis of either AUC or C6h. There were also no statistically significant differences in any of the measured or calculated pharmacokinetic parameters of the microbiologically inactive metabolite of meropenem (ICI 213,689). A total of 11 adverse experiences (one moderate and 10 mild) were reported by four patients; nine of these experiences, including two in controls, were rated by the investigator as "possibly" drug related. It is concluded that meropenem is well tolerated with repeated intravenous dosing and that dosage adjustments are not necessary for patients with hepatic disease.

The effect of the oral leukotriene antagonist, ICI 204,219, on leukotriene D4 and histamine-induced cutaneous vascular reactions in man.

Eighteen normal male subjects were recruited for a double-blind, placebo-controlled, randomized, two-period crossover study to determine the effects of a new, potent, highly selective, oral peptide leukotriene antagonist (ICI 204,219) on cutaneous vasculature. Skin testing for leukotriene D4 (LTD4) and histamine was performed at three different time intervals after receiving ICI 204,219 or placebo. The LTD4 threshold dose responses were recorded in duplicate to verify reproducibility. These data confirm known remarkable dose-response variation of cutaneous vascular reactions to LTD4 since some subjects reacted to a dose as low as 0.001 fmol. Twelve subjects (67%) demonstrated a more than one-half log increase in their threshold response after receiving ICI 204,219. Five of these 12 subjects (28%) had greater than 1 log-dose response after ICI 204,219. Two of these subjects (11.1%) had a 5 or 10 log increase in their threshold response after receiving ICI 204,219. Given the role of leukotrienes as potentially important mediators in immediate-type reactions, our results raise the possibility for additional investigation of the antagonistic effect of ICI 204,219 in nonallergic and allergic cutaneous diseases.

Inhibition of leukotriene D4-induced bronchoconstriction in normal subjects by the oral LTD4 receptor antagonist ICI 204,219.

The sulfidopeptide leukotrienes may play a role in the pathogenesis of asthma. Previous clinical trials with leukotriene antagonists have shown only minimal protection from subsequent challenge with inhaled LTD4. Using a double-blind, placebo-controlled crossover design, we tested the hypothesis that the LTD4 receptor antagonist, ICI 204,219, could inhibit LTD4-induced bronchoconstriction in normal subjects. On separate days, 3 to 7 days apart, a single oral 40-mg dose of ICI 204,219 or placebo was ingested. At 2 h (Group I), 12 h (Group II), or 24 h (Group III) after the dose, six subjects in each group underwent bronchoprovocation testing with aerosolized LTD4. The airway response was assessed by measuring specific airway conductance (SGaw) and the FEV1. ICI 204,219 had no effect on baseline pulmonary function. When given 2 h before the LTD4 challenge, ICI 204,219 increased by 117-fold the concentration of LTD4 required to reduce SGaw 35%: 34 +/- 10 versus 3,965 +/- 894 micrograms/ml (placebo versus ICI 204,219; p less than 0.05). When given 12 h before the LTD4 challenge, ICI 204,219 increased by ninefold the concentration of LTD4 required to reduce SGaw 35%: 33 +/- 11 versus 304 +/- 125 micrograms/ml (p less than 0.05). When given 24 h before the LTD4 challenge, a smaller effect was found: 12 +/- 3 versus 60 +/- 24 micrograms/ml (p less than 0.05). Plasma levels of ICI 204,219 correlated with efficacy across groups (r = 0.83, p less than 0.001), but imperfectly within groups. No adverse effects (symptoms or abnormal laboratory test results) were noted after ingesting the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Cefotetan pharmacokinetics in volunteers with various degrees of renal function.

Twenty-six volunteers with various degrees of renal function were given a single 1-g dose of cefotetan intravenously over 30 min. Concentrations of cefotetan and cefotetan tautomer in plasma and urine were determined by high-performance liquid chromatography. The pharmacokinetic parameters for cefotetan were calculated according to a two-compartment open model. The mean plasma cefotetan concentration at the end of the intravenous infusion did not vary with renal function and ranged between 122 and 126 micrograms/ml. The mean terminal half-life was 4.2 h in normal volunteers and 9.9 h in volunteers with moderate renal impairment. There was a significant linear correlation between the systemic clearance of cefotetan and creatinine clearance. The cumulative amount of cefotetan excreted in the urine over 24 h in normal volunteers was approximately 49% of the dose, but this was reduced in volunteers with moderate renal impairment. The mean urinary cefotetan concentrations generally peaked during the 2- to 4-h interval after dosing. Cefotetan tautomer was sporadically detected in the plasma and urine of approximately 50% of the volunteers. The mean plasma cefotetan tautomer concentrations and mean total cumulative urinary recoveries of cefotetan tautomer were only minimal compared with those for cefotetan. The mean percentage of the dose excreted in the urine as cefotetan tautomer was not significantly affected by the degree of renal impairment. Recommendations for the dosing of cefotetan in renal-impaired patients are given.

Interactions between tumor-promoting agents and histones studied by circular dichroism.

As part of an attempt to uncover the molecular basis of tumor promotion, the effects of the tumor promoters 12-0-tetradecanoylphorbol-13-acetate (TPA), sodium dodecyl sulfate, cholic acid and polyoxyethylene sorbitan monostearate (Tween 60) on conformations of histones in 0.14 M NaF, pH 7.8, were studied by the circular dichroism technique. A common property of the promoters was their ability to increase the asymmetric environment of the aromatic side chains of "inner histones" H2B and H4 and a H2A - H4 mixture. TPA was effective at TPA/histone molar ratios as low as 0.03. The order of activity of TPA and Tween 60 resembled their activity in tumor promotion, i.e., TPA much greater than Tween 60. TPA and Tween 60 had no effects on the tertiary structure of "outer histone" H1.