Pharmacokinetic interaction between efavirenz and rifampicin in healthy volunteers.

OBJECTIVE: Rifampicin induces the metabolism of efavirenz in humans. This study evaluated efavirenz bioavailability after rifampicin administration to healthy volunteers. METHODS: A 3-week, before-and-after trial was performed on 8 healthy volunteers. The pharmacokinetic parameters were: plasma drug concentration-time profile from 0 to 72 h (AUC0-72), plasma drug concentration-time profile from 0 h to infinity (AUC0-inf), maximal drug concentration (Cmax), time to reach maximal drug concentration (tmax), and time to reach half the initial drug concentration in elimination phase (t1/2). After an overnight fast, the volunteers ingested one efavirenz 600 mg tablet, then blood samples were drawn to evaluate plasma efavirenz levels at 0, 2, 3, 4, 5, 6, 24, 72, 120, and 168 h. The procedure was repeated after a 1-week induction period of 450 mg/day. Paired-t test and Wilcoxon matched-pairs test were used for differences between mean concentrations. RESULTS: Baseline mean AUC0-72 was 46.80 ± 9.27 µg/ml.h, AUC0-inf was 96.38 ± 38.10 µg/ml.h, Cmax 2.19 ± 0.68 µg/ml.h, tmax 4.50 ± 0.93 h, and t1/2 96.60 ± 42.38 h. Post-induction values were significantly increased: AUC0-72 9.53 ± 11.26 µg/ml.h (p < 0.05; CI95% = 0.112 - 18.940), AUC0-inf 37.24 ± 42.43 (p < 0.05; CI95% = 0.021 - 0.406) µg/ml.h, and tmax 1.13 ± 0.99 h (p < 0.05; CI95% = 0.296 - 1.953). No significant reduction occurred in post-rifampicin induction means of Cmax and t1/2. CONCLUSION: Co-administration of a single dose of efavirenz 600 mg/day with 1-week rifampicin 450 mg/day significantly reduced efavirenz bioavailability in healthy volunteers.

External quality assessment scheme for blood coagulation.

The aim of setting an External Quality Assessment Scheme (EQAS) for Blood Coagulation is to achieve a harmonization among the participating laboratories on blood coagulation testing. In Indonesia EQAS for blood coagulation is organized by the Department of Clinical Pathology, Faculty of Medicine, University of Indonesia which cooperates with the Indonesian Society of Clinical Pathologists, Jakarta Chapter. Currently coagulation tests in Indonesia are only performed in a limited number of laboratories especially in the hospital. Therefore only 65 laboratories participated in the first trial of EQAS. The control material for EQAS was provided by Organon Teknika and parameters involved in the first trial were PT, INR, APTT, and fibrinogen. Currently there are 7 brands of reagents for coagulation tests available in the market, i.e.: Behring, Biomerieux, Biopool, Human, Nycomed, Organon, and Ortho. In the evaluation, the results of each participant were compared to the median of participants who used the same reagent. If the number of participants using a given reagent was less than 10, then the result of each participant was compared to the median of overall participants. The result of a given parameter was classified as within consensus if it fell into the range of median +/- 15%. In the overall evaluation, the percentage of participants which was classified as within consensus for PT, INR, APTT, and fibrinogen were 68%, 64%, 63%, and 67%, respectively, but the CV for PT, INR, APTT, and fibrinogen were 19.84%, 17.89%, 20.21%, and 23.96% respectively. In the evaluation of participating laboratories using Behring's reagent, the percentages of participants classified as within consensus for PT, INR, APTT, and fibrinogen were 72%, 82%, 54%, and 74%, respectively. For Organon's product users, the percentages of those parameters were 84.6%-90%, 48%-75%, 86%, and 67%, respectively. It is concluded that around two-thirds of overall participating laboratories achieved harmonization in the results of coagulation test, but the variation of all parameters is still wide.

Butyrylcholinesterase and C5+ variant in a Javanese ethnic group in Indonesia.

OBJECTIVE: This study was designed to investigate the butyrylcholinesterase (BChE) and C5 variant phenotypes in a Javanese ethnic group in Indonesia. BLOOD-DONORS, MATERIALS AND METHODS: Random blood samples from a Javanese ethnic group were obtained from the Indonesian Red Cross Service. The donors were 40.09 +/- 9.53 years old, consisting of 358 (89.45%) males and 42 females (10.55%). The plasma content of BChE was determined spectrophotometrically using benzoylcholine as substrate, and phenotyping of BChE was performed using the inhibitors 10 microM dibucaine and 50 microM sodium fluoride. Phenotyping of the C5+ variant was carried out by means of polyacrylamide gel electrophoresis using a 7.5% (w/v) acrylamide slab gel and a 3% (w/v) acrylamide stacking gel, and stained with fast red azo dye. RESULTS: The results show that of 398 samples studied, the average activities of BChE are 1.00 +/- 0.22 U/ml. 377 individuals (94.72%) show normal activities, whereas 21 individuals (5.78%) are below normal (< 0.690 U/ml). The mean +/- SD of dibucaine number (DN) is 83 +/- 5 and the fluoride number (FN) is 66 +/- 6. From this population we identified one individual with UA phenotype (total activity: 0.310 U/ml, DN: 62, and FN: 50). The frequency of C5+ variant in the population as detected by acrylamide electrophoresis is 21%. CONCLUSION: Our data indicate that the atypical allele of BChE is rare and that the C5+ variant is detected in high frequency in the ethnic Javanese of Indonesia.

Country report: the Indonesian NEQAS on hematology. National External Quality Assessment Scheme.

Around six hundred clinical laboratories in all the province of Indonesia participated the Indonesian National External Quality Assessment Scheme (NEQAS) on Hematology (Program Nasional Pemantapan Kualitas Laboratorium Klinik bidang Hematologi). Automated analyzer gave better results compared to the manual method. For hemoglobin, the CV of automated analyzer and manual method were 2.8% and 9.1%, respectively. The CV of automated analyzer and manual method for leukocyte count were 8.3% and 32.3%; for erythrocyte count were 9.7% and 80.8%; and for thrombocyte count were 10.3% and 45.9%. We observe no significant improvement of the overall performance from 1986 to 1998. Quality control material for NEQAS on hematology is still a problem. The artificial particles seem not behave exactly like the human cells (leukocytes, thrombocytes).

Simultaneous measurement of proguanil and its metabolites in human plasma and urine by reversed-phase high-performance liquid chromatography, and its preliminary application in relation to genetically determined S-mephenytoin 4'-hydroxylation status.

A simple high-performance liquid chromatographic (HPLC) assay method was developed for the measurement of proguanil (PG) and its major metabolites, cycloguanil (CG) and 4-chlorophenyl-biguanide (CPB), in human plasma and urine. The assay allowed the simultaneous determination of all analytes in 1 ml of plasma or 0.1 ml of urine. The detection limits of PG, CG, and CPB, defined as the signal-to-noise ratio of 3, were 1 and 5 ng/ml for plasma and urine samples, respectively. Recoveries of the analytes and the internal standard (pyrimethamine) were > 62% from plasma and > 77% from urine. Intra-assay and interassay coefficients of variation for all analytes in plasma and urine were < 10% except for the values of CG and CPB, which ranged from 10% to 15% at one or two concentrations among 4-5 concentrations studied. The clinical applicability of the method was assessed by the preliminary pharmacokinetic study of PG, CG, and CPB in six healthy volunteers with the individually known phenotypes (extensive and poor metabolizers) of S-mephenytoin 4'-hydroxylation, suggesting that individuals with a poor metabolizer phenotype of S-mephenytoin have a much lower capacity to bioactivate PG to CG compared with the extensive metabolizers.

Metabolic disposition of proguanil in extensive and poor metabolisers of S-mephenytoin 4'-hydroxylation recruited from an Indonesian population.

1. The metabolism of proguanil (PG) was studied by measuring PG, cycloguanil (CG) and 4-chlorophenylbiguanide (CPB) in plasma and urine samples after an oral 200 mg dose of PG hydrochloride administered to 14 extensive (EMs) and 10 poor hydroxylators (PMs) of S-mephenytoin of Indonesian origin. 2. The mean ( +/- s.d.) values of the elimination half-life (t 1/2) and AUC of PG were significantly (P < 0.01) greater in the PM than in the EM group (20.6 +/- 3.1 vs 14.6 +/- 3.5 (95% confidence intervals of difference 3.1 to 8.9) h; and 5.43 +/- 1.89 vs 3.68 +/- 0.83 (0.58 to 2.91) micrograms ml-1 h). 3. Plasma concentrations of CG, an active metabolite, could not be detected in all PMs, and those of CPB were sufficiently high to determine a time-course in only four PMs. Mean AUC(0,24 h) values of CPB were significantly (P < 0.05) lower in the PM (n = 4) than in the EM group (n = 14) (0.47 +/- 0.13 vs 0.88 +/- 0.50 (-0.14 to 0.96) micrograms ml-1 h). 4. Log10 percentage urinary recovery of 4'-hydroxymephenytoin correlated significantly (P < 0.05) with the t 1/2 (rs = -0.661) and AUC (rs = -0.652) of PG. 5. PG, CG and CPB were detectable in urine at 12 h in all subjects. Log10 percentage urinary recovery of 4'-hydroxymephenytoin correlated significantly (P < 0.01) with urinary PG/CG (rs = -0.876), PG/CPB (rs = -0.833) and PG/(CG + CPB) (rs = -0.831) metabolic ratios.(ABSTRACT TRUNCATED AT 250 WORDS)

Dapsone N-acetylation, metoprolol alpha-hydroxylation, and S-mephenytoin 4-hydroxylation polymorphisms in an Indonesian population: a cocktail and extended phenotyping assessment trial.

We examined dapsone N-acetylation and metoprolol alpha-hydroxylation and S-mephenytoin 4-hydroxylation phenotypings using the respective test probes (dapsone and racemic metoprolol and mephenytoin) administered separately and in a cocktail manner to an Indonesian subject group (n = 30). After ascertaining that the separate and cocktail phenotyping tests of the probe drugs correlated with each other (all rs values > 0.84; p < 0.001), the cocktail phenotyping assessment was extended to the other 74 Indonesians. In a total of 104 Indonesians phenotyped with the cocktail test, a visual antimode was apparent only in the dapsone N-acetylation and S-mephenytoin 4-hydroxylation polymorphisms: the frequencies of slow acetylators and poor hydroxylators were 43.3% (95% confidence interval, 33.7% to 52.8%) and 15.4% (95% confidence interval, 8.5% to 22.3%), respectively. The distribution histogram and probit plots of the metabolic ratio of metoprolol gave no clear evidence for bimodality, and therefore no poor alpha-hydroxylator of metoprolol was considered to exist in the present sample size. The findings indicate that the Indonesian subjects have a greater incidence of slow acetylator phenotype compared with Japanese and Chinese, as well as a frequency of poor metabolizer phenotype of S-mephenytoin similar to that of Korean and Chinese subjects. They resemble an African population (Nigerians) in metoprolol alpha-hydroxylation polymorphism, with no apparent antimode derived from white populations.

PF3 activity in normal subjects and beta-thalassemia trait.

Platelet factor 3 (PF3) is a platelet membrane component that plays an important role in the activation of the coagulation mechanism. Whenever platelet activation occurred, PF3 is released and participates in thrombin formation. Erythrocyte membrane fraction has also some PF3 like activity, and in abnormal erythrocyte membrane disorders, eg thalassemia, some of the membrane fraction accelerates platelet activation by increasing the PF3 activity. Formerly it was difficult to measure the PF3 activity in plasma. Recently a sensitive chromogenic test to determine the PF3 activity, which could detect the changes in PF3 activity with time, was introduced. This study was done to observe the effect of abnormal erythrocyte on platelet activation. The results obtained using the chromogenic method are the following: whole blood taken from normal subjects showed OD 0.11 +/- 0.06 at 0 minutes after blood collection and then increased significantly (p < 0.01) to 0.21 +/- 0.10 after 90 minutes, while the platelet count did not differ significantly (p > 0.05). Those results showed that there were some platelet activation after 90 minutes as seen by the increased PF3 activity, with no significant change in platelet counts. In beta-thalassemic trait subjects the PF3 activity in whole blood at 0 minutes did not differ significantly compared to the normal subjects, but after 90 minutes it was significantly higher (p < 0.01), OD 0.52 +/- 0.35. However the PF3 in platelet rich plasma at 90 minutes did not increase. The platelet count after 90 minutes was significantly decreased (p < 0.01) This result suggest that the increase in PF3 activity was caused by the role of the abnormal erythrocytes.

The effect of Norplant on some hemostatic parameters in Indonesian women.

Many reports have indicated that oral contraceptives can increase the incidence of thromboembolic disorders. Norplant, an implant contraceptive containing levonorgestrel, has been developed recently. The aim of this study is to observe the effect of Norplant on some hemostatic parameters. The subjects in this study were divided into 5 groups. Group 1 (control) consisted of 25 female blood donors. Group 2 (N = 25), group 3 (n = 25), group 4 (n = 17) and group 5 (N = 20) consisted of subjects who had been using Norplant for 2, 3, 4, and 5 years, respectively. Prothrombin time, activated partial thromboplastin time, fibrinogen level, assay of F VII and X, antithrombin III activity, plasminogen activity, alpha 2-plasmin inhibitor activity and platelet aggregation test were done in all subjects. Our results showed that there was a significant difference (p < 0.05) on platelet aggregation induced by 10 microM of ADP between the control group and Norplant users for more than 2 years, while the other parameters did not differ significantly. It is concluded that 5 years users of Norplant did not alter blood coagulability, but increased platelet response to 10 microM of ADP.

Bioavailability of rifampicin caplets (600 mg and 450 mg) in healthy Indonesian subjects.

A bioavailability study of rifampicin 450 mg caplets and rifampicin 600 mg caplets was carried out in 20 healthy male subjects. The higher dose was administered to subjects with a body weight greater than 50 kg. Subjects were divided into two groups where group 1 was treated with a single oral dose of 450 mg rifampicin in fasting condition. Group 2 was treated in the same way as group 1, but with a dose of 600 mg rifampicin. Our results in group 1 show peak heights of serum levels of rifampicin ranging from 13.6 to 21.0 micrograms X ml-1 (mean value was 17.6 micrograms X ml-1). AUC values ranged from 81.1 to 177.9 micrograms X ml-1h (mean value was 145.2 micrograms X ml-1 h.) Respective figures with 600 mg rifampicin were 11.0 to 27 micrograms X ml-1 (mean = 20.0 micrograms X ml-1) for peak heights and 132.0 to 260.6 micrograms X ml-1h (mean value = 181.1 micrograms X ml-1h) for AUC. In vitro dissolution tests were conducted on the same batch of respective products. Results show that maximum dissolution occurred in 15 minutes. It is concluded that our results were rather high compared to what has been reported so far. It has been suggested to reduce the dose to body weight ratio for rifampicin.