High-performance liquid chromatographic method for the determination of ivermectin in plasma.

A simple, sensitive, selective and reproducible method based on reversed-phase chromatography was developed for the determination of ivermectin in human plasma. The internal standard (moxidectin) was separated from ivermectin on a Hypersil Gold C18 column (150 x 4.6 mm, 5 microm particle size), with retention time of 3.7 and 7.0 minutes, respectively. Fluorescence detection was set at an excitation and emission wavelength of 365 and 475 nm, respectively. The mobile phase consisted of acetonitrile, methanol and distilled water (50:45:5, v/v/v), running through the column at a flow rate of 1.5 ml/minute. The chromatographic analysis was operated at 25 degrees C. Sample preparation (100 microl plasma) was done by a single step protein precipitation with acetonitrile, followed by derivatization with 100 microl of N-methylimidazole solution in acetonitrile (1:1, v/v) and 150 microl of trifluoroacetic anhydrous solution in acetonitrile (1:2, v/v). Calibration curve over the concentration range of 20-8000 ng/ml plasma was linear with correlation coefficient better than 0.995. The precision of the method based on within-day repeatability and reproducibility (day-to-day variation) was below 15% (coefficient of variation) Good accuracy was observed for both intra-day and inter-day assays, as indicated by the minimal deviation of mean values found with measured samples from that of the theoretical values (below +15%). Limit of quantification was 0.02 ng using 100 microl sample. The mean recovery for ivermectin and the internal standard was greater than 90%. The method was free from interference from endogenous substances and commonly used drugs. The method appears to be robust and has been applied to the investigation of plasma concentration vs time profile of ivermectin in five healthy Thai volunteers following a single oral dose of 200 microg ivermectin/kg body weight.

An alternative high-performance liquid chromatographic method for determination of clindamycin in plasma.

A simple, sensitive, selective and reproducible method based on a reversed-phase chromatography was developed for the determination of clindamycin in human plasma. Clindamycin was separated from the internal standard (phenobarbital) on a Luna C18 column (250 x 4.6 mm, 5 mm particle size: Phenomenex, USA), with retention times of 5.6 and 14.2 minutes, respectively. Ultraviolet detection was set at 210 nm. The mobile phase consisted of a solution of 0.02 M disodiumhydrogenphosphate (pH 2.8) and acetonitrile (76:24 v/v), running through the column at a flow rate of 1.0 ml/min. The chromatographic analysis was operated at 25 degrees C. Sample preparation (1 ml plasma) was done by a single step liquid-liquid extraction with water saturated ethylacetate. Calibration curves in plasma at concentrations of 0.25, 0.5, 1.0, 2.0, 4.0, 8.0 and 16.0 microg/ml were all linear with correlation coefficients better than 0.999. The precision of the method based on within-day repeatability and reproducibility (day-to-day variation) was below 15% (% coefficient of variations: %CV). Good accuracy was observed for both the intra-day and inter-day assays, as indicated by the minimal deviation of mean values found with measured samples from that of the theoretical values (below +/- 15%). Limit of quantification was accepted as 0.07 microg using 1 ml plasma sample. The mean recovery for clindamycin and the internal standard were greater than 95%. The method was free from interference from fosmidomycin, including commonly used drugs, antimalarials and antihelminthics. The method appears to be robust and has been applied to a pharmacokinetic study of clindamycin in a patient with malaria following oral doses of clindamycin at 10 mg/kg body weight given twice daily for 7 days.

Investigation of bioavailability, pharmacokinetics and safety of new pediatric formulations of artesunate and mefloquine.

The bioavailability/pharmacokinetics of dihydroartemisinin and mefloquine following the oral doses of 4 mg/kg body weight artesunate (Cambodian Pharmaceutical Enterprise) given concurrently with 10 mg/kg body weight oral mefloquine artesunate (Cambodian Pharmaceutical Enterprise) were investigated in 15 healthy Cambodian male volunteers. Both formulations were generally well tolerated. Both produced satisfactory plasma/blood concentration-time profiles. Oral artesunate and mefloquine were rapidly absorbed from gastrointestinal tract with marked inter-individual variation. For the dihydroartemisinin, the median (95% Cl) Cmax of 748 (304-1,470) ng/ml was observed at 1.5 (0.3-3.0) hours (tmax) after drug administration. The median (95% CI) values for AUC0-infinity, lambda(z) and tl/2z were 1.673 (1.08-2.88) microg.h/ml, 0.54(0.24-1.1)/hour and 1.3 (0.6-2.9) hours, respectively. For mefloquine, a median (95% Cl) Cmax of 1,000 (591-1,500) ng/ml was observed at 4 (2-6) hours (tmax) after drug administration. The median (95% CI) value for AUC0-168h was 3.92 (2.88-7.02) microg.h/ml.

The pharmacokinetics of oral dihydroartemisinin and artesunate in healthy Thai volunteers.

The pharmacokinetics of oral dihydroartemisinin (DHA) following the dose of 2 and 4 mg/ kg body weight dihydroartemisinin (Twisinin, T-2 Program, Thailand) and 4 mg/kg body weight oral artesunate (AS; Guilin Pharmaceutical Works, Guangxi, China) were investigated in 20 healthy Thai volunteers (10 males, 10 females). All formulations were generally well tolerated. Oral DHA was rapidly absorbed from gastrointestinal tract with marked inter-individual variation. The pharmacokinetics of DHA following the two dose levels were similar and linearity in its kinetics was observed. Based on the model-independent pharmacokinetic analysis, median (95% CI) values for Cmax of 181 (120-306) and 360 (181-658) ng/ml were achieved at 1.5 hours following 2 and 4 mg/kg body weight dose, respectively. The corresponding values for AUC0-infinity, t1/2z, CL/f and Vz/f were 377 (199-1,128) vs 907 (324-2,289) ng.h/ml, 0.96 (0.70-1.81) vs 1.2 (0.75-1.44) hours, 7.7 (4.3-12.3) vs 6.6 (3.1-10.1) l/kg, and 90.5 (28.6-178.2) vs 6.6 (3.1-10.1) ml/min/kg, respectively (2 vs 4 mg/kg dose). Oral AS was rapidly biotransformed to DHA, which was detectable in plasma as early as 15 minutes of AS dosing. Following 4 mg/kg dose, median (95% CI) value for Cmax of 519 (236-284) ng/ml was achieved at 0.7 (0.25-1.5) hours. AUC0-infinity, and t1/2z were 657 (362-2,079) ng.h/ml, 0.74 (0.34-1.42) hours, respectively. Cmax of DHA following oral AS were significantly higher, but total systemic exposure was greater following oral DHA at the same dose level (4 mg/kg body weight). There was no significant sex difference in pharmacokinetics of DHA.

Successful eradication of Ascaris lumbricoides and hookworm infection after three repeated doses of albendazole.

Three repeated orally doses of albendazole 400 mg in 6 weekly intervals were evaluated in Thai hill-tribe students who had at least one kind of soil-transmitted helminths (i.e. Ascaris lumbricoides, hookworm and Trichuris trichiura). Stool examination and parasite egg count were performed using Beaver's standard direct smear method and Kato-Katz's cellophane thick smear method prior to treatment and then 1 month after the first, second and third dose of drug administrations. A single dose of albendazole was very effective against A. lumbricoides and hookworm infections, with cure rates of 98.68 per cent and 92.16 per cent, respectively. The second and third dosages eradicated A. lumbricoides and hookworm infections, respectively. Conversely, the first to third cure rates for T. trichiura infection were relatively low, being 37.76-58.16 per cent. Three repeated doses of albendazole proved to be beneficial in eradication of A. lumbricoides and hookworm infections, and decreased the prevalence of T. trichiura infected cases. For eradication of T. trichiura infection, further regimen and period of drug administration is required.

Characterization of specific monoclonal antibodies for detection of mefloquine in body fluids.

Specific monoclonal antibodies (MAbs) to mefloquine conjugated to bovine serum albumin (mefloquine-BSA) were produced by hybridoma technology. The mefloquine-BSA was synthesized by converting mefloquine into hemisuccinate followed by convalently linked to bovine serum albumin (BSA) and coupling with N,N' disuccinimidyl carbonate (DSC). The conjugate was purified by Sephadex G-75 gel filtration using 0.01 M PBS pH 7.2. An average of 19.34 molecules of mefloquine were conjugated to each molecule of protein determined by differential UV absorption spectra of hapten and protein carrier. Sixteen monoclones producing antibody specific to mefloquine were screened by indirect ELISA using homologous antigens. The specificity of MAbs was determined by reacting with BSA and the structurally related antimalarial drug, quinine. Three, three, five and two MAbs belonged to IgG1, IgG2a, IgG2b and IgG3, respectively. Most of the MAbs slightly reacted with quinine-BSA due to the closely related structure of mefloquine to quinine. The selected MAb designated 11F9(G5)G9 which showed no cross reaction with quinine-BSA gave high reactivity with blood samples from malaria patients previously treated with mefloquine when compared to normal blood by indirect ELISA. The preliminary results indicated that such specific MAb could be used as antibody probe for detection of mefloquine in biological fluids.

Ex vivo blood schizontocidal activities of artemisinin derivatives against Plasmodium falciparum.

Serum samples collected at intervals from eight healthy volunteers after the administration of the six regimens of artemisinin derivatives were investigated for their ex vivo blood schizontocidal activities against K1 strain Plasmodium falciparum. The regimens included single doses of (a) 300 mg oral artemether; (b) 300 mg intramuscular artemether; (c) 100 mg suppository artemether; (d) 300 mg oral artesunate (Guillin formulation); (e) 300 mg oral artesunate (Arenco formulation); (f) 300 mg oral dihydroartemisinin. Sera collected after various regimens of artemisinin derivatives showed distinct degree of ex vivo blood schizontocidal activities. Activity of sera after suppository dosing was remarkably low and variable comparing to the other two formulations (oral, intramuscular). Median values for Amax (the maximum activity normalized with dose) of sera from oral dosing were 2.4- and 118-fold, while AUA (the area under activity-time curve, normalized with dose) were 0.82- and 2,370-fold of that after the intramuscular and suppository dosing, respectively. Sera from artesunate-Arenco dosing exhibited significantly higher Amax and AUA (medians: Amax 12.4 vs 5.13 nmol/l/mg dose; AUA: 21.9 vs 8.8 nmol x h/ml/mg dose), compared to that from artesunate-Guillin dosing. Among the oral formulations of artemisinin derivatives investigated (artemether, artesunate, dihydroartemisinin), sera collected following a single dose of oral dihydroartemisinin exhibited lowest bioactivity (Amax 2.35 nmol/l/mg dose; AUA: 44 nmol x h/ml/mg dose).

Investigations of incidence of pretreatment, drug sensitivity in vitro, and plasma levels of pyrimethamine in patients with multidrug resistant falciparum malaria following the three combination regimens of artemether/pyrimethamine.

The study was carried out to investigate the status of in vitro susceptibility of Plasmodium falciparum to pyrimethamine (PYR) in multidrug resistant area of the Thai-Myanmar border, the incidence of unregulated use of the combination of PYR with sulfadoxine (Fansidar) in this area and the relevance of pharmacodynamic and pharmacokinetic factors in determining the treatment outcome from the three combination regimens of ART/PYR (1-, 2- and 3-day regimens), in patients with acute uncomplicated falciparum malaria. The majority of patients had baseline PYR concentrations in the range of 1-100 (50.6%) or 100-500 (34.8%) ng/ml, while concentrations of more than 500 ng/ml were found in only 1.1%. All of the isolates exhibited high grade resistance to PYR with the minimum inhibition concentration (MIC) of as high as 10(-5) M. No association was observed between treatment outcome and the presence of baseline plasma PYR concentrations. In addition, lack of association between plasma concentrations during the acute phase (day-1 and -2) and treatment outcome was found.

Pharmacokinetics of a single oral dose of dihydroartemisinin in Vietnamese healthy volunteers.

Pharmacokinetics of a 240 mg single dose of oral dihydroartemisinin (DHA) was investigated in 8 healthy (5 males, 3 females) Vietnamese volunteers. Plasma concentrations were measured by high-performance liquid chromatography with electrochemical detection in the reductive mode. The concentration time profile of DHA was fitted with one-compartment model with a lag time. Pharmacokinetics of DHA is comparable between males and females even when adjusted with dosage. The median (range) values of pooled pharmacokinetics of oral DHA were: t(lag) 0.41 (0.09-0.78) hours, t(1/2z) 0.58 (0.17-1.43) hours, t(max) 1.6 (1.1-2.2) hours, Cmax 466 (128-787) ng/ml. Cmax/dosage 97.7 (27.2-124.6) ng/ml, t(1/2z) 2.0 (1.5-3.4) hours, AUC 1867 (420-3535) ng x h/ml, AUC/dosage 364.3 (89.3-559.7) ng x h/ml/dosage, Cl/f 45.8 (30.0-190.0) ml/min/kg, Vz/f 8.0 (5.5-29.9) l/kg. Interindividual variation was large, the coefficients of variation (CV) were 47.8% and 45.3% respectively to AUC and Cmax. The t(max) of DHA formulation was comparable with that of DHA metabolite of artemisinin derivatives. The t(1/2z) was longer and shorter than that of DHA metabolites of oral formulations of artesunate and artemether, respectively. For monotherapeutic regimen(s) of DHA, dosing frequency of at least twice a day is suggested. Combined regimen(s) of DHA with other potent, long half-life antimalarials may also be an alternative approach.

Plasma containing artemether-pyrimethamine has ex vivo blood schizonticidal activity against Plasmodium falciparum.

Plasma samples collected at intervals from healthy volunteers, after administration of 3 drug regimens [artemether (ART) 300 mg, pyrimethamine (PYR) 100 mg, and ART 300 mg plus PYR 100 mg] were examined for blood schizonticidal activity against K1 strain and T(9/94) clone of Plasmodium falciparum ex vivo. A synergistic effect against T(9/94), a pyrimethamine sensitive clone, was observed in plasma collected after ART+PYR administration, when the test was carried out in low p-aminobenzoic acid, low folic acid medium. The maximum activity (Amax), expressed as equivalent dihydroartemisinin concentration, for plasma samples collected after the combined ART+PYR regimen [6,935 (1,330-13,400) nmol/l] was significantly higher than those for the single ART or PYR regimens [935 (397-2,000) and 9.9 (5.6-15.6) nmol/l, respectively]. In addition, the area under the activity curve (AUA) for the combined regimen [12,8397 (39,274-19,7901) nmol.h/l] was significantly higher than those for the single ART or PYR regimens [(3618 (1406-5597) or 334 (82.3-733.3) nmol.h/l, respectively]. Microscopic observation revealed that ART in the combined regimen exerted its inhibitory effect against all erythrocytic stages and that this occurred before effects of PYR activity. Prolongation of inhibitory effects for the combined ART+PYR regimen was shown to be due to PYR activity by comparison to the activity from the single ART regimen. Results clearly demonstrated no PYR activity against K1, a pyrimethamine resistant strain, in plasma samples collected after the single PYR regimen and the ART+PYR regimen. Microscopic examination confirmed that growth inhibition of K1 was caused by ART activity only.

Monoclonal antibodies to quinine.

Monoclonal antibodies (MAbs) to quinine conjugated to a carrier protein were produced. Quinine was converted into a hemisuccinate prior to covalently linked to bovine serum albumin (BSA) by reacting with N,N'-disuccinimidyl carbonate (DSC). Coupling ratio of quinine-BSA was 13:1 calculated by spectrophotometry and 14:1 by calculation from quinine standard curve. This immunogen was used for both monoclonal antibody production and for screening test, indirect ELISA. The specificity of quinine-BSA MAbs was examined by checking the cross reactivity with BSA and the structurally related antimalarial drug, mefloquine. Six MAbs belonging to IgG1 were obtained. These MAbs slightly reacted with mefloquine-BSA because of closely related structure of mefloquine to quinine and similar conjugate preparation procedure used for conjugation. One selected MAb against quinine-BSA, showed higher reactivity with blood samples from patients previously treated with quinine when compared to normal blood. This preliminary test indicated that MAbs obtained may be useful to be used as the probe for detection of quinine in biological fluids.

Pharmacokinetic interactions of artemether and pyrimethamine in healthy male Thais.

The pharmacokinetics of a single oral dose of artemether (300 mg) and pyrimethamine (100 mg) given as each individual drug alone or as a drug combination (artemether 300 mg plus pyrimethamine 100 mg), were investigated in 8 healthy male Thai volunteers. Both artemether and pyrimethamine were rapidly absorbed after oral administration. Elimination of pyrimethamine was however, a relatively slow process compared with artemether, and thus resulted in a long terminal phase elimination half-life (50-106 hours). Pharmacokinetics of artemether and dihydroartemisinin following a single oral dose of artemether alone or in combination with pyrimethamine were similar. In contrast, coadministration of artemether resulted in significantly increased Cmax (medians of 818 vs 1,180 ng/ml) and contracted the apparent volume of distribution (medians of 3 vs 2.56 l/kg) of pyrimethamine.

Pharmacokinetics and ex vivo anti-malarial activity of sera following a single oral dose of dihydroartemisinin in healthy Thai males.

The pharmacokinetics of dihydroartemisinin (DHA) was studied in eight healthy male Thai subjects after a single oral dose of 300 mg. Absorption of oral DHA was rapid, Cmax of 679 (307-1000) ng/ml was observed at 1.5 (1-2.5) hours after dosing [median (range)]. Plasma concentrations declined monoexponentially and at 12 hours after administration, the levels were below the detection limit (3 ng/ml). A large variation in the AUC (approximately) 50% was observed. The median (range) AUC was 2010 (636-4079) ng h/ml. The lag time and absorption half-life (t1/2a) were 0.169 (0.111-0.277) hours and 0.709 (0.367-1.118) hours respectively. t1/2z was 1.25 (0.79-1.89) hours Vz/f and CL/f were 5.9 (3.5-8.2) l/kg and 45.3 (28.6-122.8) ml/min/kg, respectively. The pattern of its ex vivo serum activity coincided with the plasma concentrations of DHA.

Effect of artemether on electrocardiogram in severe falciparum malaria.

The effect of intramuscular artemether (intramuscular loading dose of 160 mg, followed by 80 mg daily for another 6 doses), in comparison with that of quinine (intravenous infusion of loading dose of 20 mg/kg, followed by 10 mg/kg q 8 hourly for 7 days), on the electrocardiograph of severe falciparum malaria patients were investigated in 102 Thai patients (92 males, 10 females) admitted to Pra Pokklao Hospital, Chantaburi, southeast of Thailand. Fifty patients (19 with quinine and 31 with artemether) were eligible for ECG analysis. Hypotension was found significantly more common in the quinine group (13 vs 2 cases). Thirteen, 5 and 1 patients with quinine treatment, respectively, had tachycardia, non-specific T-wave change and QTc prolongation. No significant dysrhythmia was found despite high plasma quinine concentrations. Five patients died; their ECGs were not significantly different from those who survived. In the group with intramuscular artemether, 17 cases had tachycardia prior to artemether treatment. QTc prolongation and non-specific T-wave change were found in 2 and 6 cases. One patient had RBBB and second degree AV-block on Day 1, but returned to normal on Day 2. No other dysrhythmia or other significant changes in ECG tracing which would suggest any effect of artemether on cardiovascular system were observed.

Activity of artemether-azithromycin versus artemether-doxycycline in the treatment of multiple drug resistant falciparum malaria.

The efficacy of the combination of artemether with doxycycline or azithromycin was evaluated in 60 patients with acute uncomplicated falciparum malaria who attended malaria clinic in Mae Sot, Tak Province (Thai-Myanmar border). Patients (30 each) were randomized to receive (a) 300 mg artemether together with 100 mg doxycycline as initial doses, followed by 100 mg artemether plus 100 mg doxycycline at 12 hours later, then 100 mg doxycycline every 12 hours for another 4 days, or (b) 300 mg artemether together with 500 mg azithromycin, followed by 250 mg azithromycin at 24 and 48 hours. The follow-up period was 28 days. Patients in either group had a rapid initial response to treatment with comparable PCT and FCT. The cure rate of artemether-azithromycin regimen was significantly lower than that of artemether-doxycycline regimen (14.8 vs 53.3%). Low cure rate from artemether-azithromycin combination in this study was likely to be due to inadequate azithromycin dosage. However, with the low incidence of gastrointestinal adverse effects, the once daily dose of azithromycin could still be increased in order to enhance its clinical efficacy. The simplicity of drug administration and lesser incidence of adverse effects make azithromycin a more proper partner of artemether than doxycycline. Further dose-finding and pharmacokinetic study with the artemether-azithromycin combination is encouraging.

Artemether-pyrimethamine in the treatment of pyrimethamine-resistant falciparum malaria.

In vitro susceptibility and clinical response of multidrug resistant Plasmodium falciparum to the combination artemether-pyrimethamine were evaluated in patients with acute uncomplicated falciparum malaria. Sixty patients were randomized to receive 3 oral regimens of the combination artemether-pyrimethamine as follows: Regimen-I: artemether (300 mg) plus pyrimethamine (100 mg) on the first day, then placebo on the two consecutive days; Regimen-II: artemether (300 mg) plus pyrimethamine (100 mg) on the first day, then artemether (150 mg) plus pyrimethamine (50 mg) on the second day, and placebo on the third day; Regimen-III: artemether (300 mg) plus pyrimethamine (100 mg) on the first day, then artemether (150 mg) plus pyrimethamine (50 mg) on the second and third days. All patients had a rapid initial response to treatments with 95% of parasitemia being cleared within the first 24 hours. PCT24hours and PCT48hours were similar among the three drug regimens (11 vs 4, 6 vs 12, and 9 vs 11 patients for a 1-day, 2-day, and 3-day combination regimen, respectively). Fever was cleared within 48 hours in all patients in either group. Transient mild nausea, vomiting and loss of appetite were found in a few patients during the first 2 days of treatment. Seven patients did not complete the 28 day follow-up period (5 vs 2 in a 1-day vs 2-day regimen), the reason for withdrawal was not associated with drug-related adverse effects. Only 53 patients were therefore qualified for the efficacy assessment. There was 15, 13 and 5 patients in a 1-day, 2-day and 3-day combination regimens, respectively, who had reappearance of the parasitemia between days 11 and 21. The cure rates of the 3 treatment groups were statistically significantly different (0, 27.8, and 75% for a 1-day, 2-day and 3-day combination regimen, respectively). Two patients developed P. vivax malaria on days 20 and 24. All of the isolates were highly resistant to pyrimethamine, with MIC of 10(-5) M. There is potential advantage of this combination therapy in reducing the dosage and treatment period of artemisinin derivative, which is therefore likely to improve complaince in clinical practice. The use of a 3-day combination regimen (300 mg artemether plus 100 mg pyrimethamine on the first day, then 150 mg artemether plus 50 mg pyrimethamine on the second and third days) seems to be a good alternative regimen to sulfadoxine/ pyrimethamine in areas where P. falciparum is sensitive to pyrimethamine eg in Africa.

Quinine-tetracycline for multidrug resistant falciparum malaria.

Plasmodium falciparum in Southeast Asia is highly resistant to chloroquine and sulfadoxine/ pyrimethamine. Quinine-tetracycline has been used as a second line treatment for uncomplicated falciparum malaria, but duration of treatment varies from place to place. The 7-days course of this combination has been shown to be very effective. However, due to the cinchonism adverse effects, the patient compliance has not been satisfactory. We have evaluated the efficacy of a 7-days course of tetracycline in combination with either 5 or 7-days course of quinine. Ninety male Thai patients who were admitted to the Bangkok Hospital for Tropical Diseases were randomized to receive tetracycline 250 mg qid for 7 days in combination with either quinine 600 mg tid for 5 days (Q5T7; group A) or quinine 600 mg tid for 7 days (Q7T7; group B). The patients were hospitalized for 28 days. Patients in both groups had a comparable initial response to treatment, with the clearance of fever and parasites within 4 days. There were 46 and 40 patients in group A and B, respectively, who completed the 28 day of follow-up. The cure rates were 87 and 100%, respectively for group A and B. No serious adverse effects were found in either group; transient nausea, vomiting and tinnitus were common findings. The incidence of adverse effects was not different between the two groups. The results from the present study suggest that a short course treatment of quinine (Q5T7) had significantly decreased the cure rate. In areas with quinine resistant falciparum malaria, a full course of 7-days quinine, in combination with 7-days course of tetracycline is recommended for hospital treatment. However, an alternative shorter course of antimalarials is suggested for home treatment.

Plasma concentrations of praziquantel during the therapy of neurocysticerosis with praziquantel, in the presence of antiepileptics and dexamethasone.

Plasma praziquantel concentrations were measured in 11 Thai patients with active neurocysticercosis (8 males and 3 females). Praziquantel (Biltricide 600 mg per tablet) was given at a daily dose of 45 mg/kg given in 3 divided doses for 15 consecutive days. All patients had significant improvement with resolution of symptoms and signs, and reduction of active lesions of cysticercosis shown by the brain computed tomographic scanning. After oral administration, the drug was rapidly absorbed from the gastrointestinal tract. There was substantial inter-individual variability in plasma concentrations of praziquantel. After the first dose, maximum plasma concentrations in the range of 42-540 ng/ml was attained at 30 minutes to 5 hours. In all cases, the drug almost totally disappeared from plasma within 8 hours; drug levels measured prior to the first doses on the following days showed undetectable levels. The area under the plasma concentration-time curves of praziquantel following the first dose were between 125 and 990 ng hour/ml. The results suggested that the unusual low plasma availability of the drug observed in this group of patients could be a consequence of pharmacokinetic drug interactions of the concomitant therapy with antiepileptic drugs and dexamethasone. Active metabolite(s), rather than praziquantel itself, may play a significant part in the therapy of neurocysticerosis.

Artemether 5 versus 7 day regimen for severe falciparum malaria.

Twenty-eight male Thai patients with severe falciparum malaria were randomized to receive either artemether for a 5 (300 mg initial dose followed by 100 mg for another 4 days) or a 7 days regimen (160 mg initial dose, followed by 80 mg daily for another 6 days). Thirteen patients received a 5 day regimen and 15 received 7 day regimen. The follow-up period was 28 days. The patients in both groups were comparable in age, body weight, admission parasitemia, hematocrit and white cell count. There were 4 patients in each group who presented with cerebral malaria. The median values of parasite and fever clearance times (PCT and FCT) in the 5 and 7 days regimens were 52 vs 60 hours, and 85 vs 68 hours, respectively. There were 8 and 4 patients, respectively who had recrudescence during days 15 to 25. The cure rates were 38% (95% CI = 14-68%) and 73% (95% CI - 50-96%), respectively for 5 and 7 day regimens. None died in either group. No patients in either group had neurological sequelae after recovery of consciousness. Clinically adverse effects in either group were transient pain at the site of injection. No drug related biochemical or ECG changes were noted in either group. The duration of treatment is the determinant of the cure rate; however, the duration of even 7 days still resulted in high recrudescence rate. It may be necessary to combine artemether with other longer half-life antimalarials to improve the cure rate.