A randomized comparison of chloroquine, amodiaquine and their combination with pyrimethamine-sulfadoxine in the treatment of acute, uncomplicated, Plasmodium falciparum malaria in children

The increasing resistance of Plasmodium falciparum to antimalarial monotherapy (MT) has created an urgent need for the evaluation of alternative effective, safe, cheap, readily available and affordable, combination treatments (CT) with antimalarial drugs. In the present study, the efficacies of chloroquine (CQ) or amodiaquine (AQ) in the oral treatment of acute, symptomatic, uncomplicated, Plasmodium falciparum malaria were compared with those of oral treatments with the combination of CQ or AQ with pyrimethamine-sulfadoxine (PS). The CQ and AQ were each given at a dose of 10 mg/kg.day for 3 days (days 0, 1 and 2), with or without PS given as a single dose (25 mg sulfadoxine/kg) at presentation (day 0). Overall, 303 children aged 0.5-10 years (74 given CQ, 82 AQ, 72 CQPS and 75 AQPS) were evaluated. The fever-clearance time (FCT) was significantly shorter in those treated with AQPS than in those treated with CQ or CQPS. The proportions of patients with complete clearance of their parasitaemias on days 1 and 2 were significantly larger and the parasite-clearance times (PCT) were all significantly shorter with the drug combinations than with their corresponding MT. For example, the mean (S.D.) PCT were 2.6 (0.8) days for CQ v. 2.1 (0.8) days for CQPS (P=0.0002), and 2.6 (0.7) days for AQ v. 2.1 (0.7) days for AQPS (P=0.00001). The cure 'rates' on days 14, 21 and 28 were also significantly higher with AQ, CQPS and AQPS than with CQ; those on day 28, for example, were 47.2%, 98.7%, 100% and 100% for CQ, AQ, CQPS and AQPS, respectively (P=0.000001). Gametocyte carriages on day 3 or on days 3, 7 and/or 14 combined were significantly lower in those treated with CQPS than in those given CQ; there was no gametocyte carriage in the CT groups on day 28. In the CQ group, eight of 13 children with gametocytaemia on day 3 had a response indicative of resistance. However, the five CQ-resistant infections that were re-treated with AQPS responded promptly, with a PCT significantly shorter than that during the initial treatment with CQ and with a cure 'rate' of 100% on day 28. Adverse reactions to treatment were similar on the first and subsequent days of treatment and were tolerable except for pruritus, which was significantly more common in children treated with CQ alone than in the other treatment groups. Haematological and biochemical parameters were not adversely affected by any treatment. The CQPS and AQPS combinations appear to be well tolerated and may be useful as alternatives to monotherapy with CQ or AQ as resistance to the single drugs develops.

Comparative clinical characteristics and responses to oral 4-aminoquinoline therapy of malarious children who did and did not develop 4-aminoquinoline-induced pruritus

The clinical characteristics and the responses to oral 4-aminoquinoline therapy of 150 malarious children presenting consecutively were investigated in an endemic area. At presentation, the 75 children who subsequently developed pruritus were significantly older and had significantly higher body temperatures than the 75 children who did not develop pruritus. There were no other significant differences in clinical presentation between the two groups. In children with pruritus, there was no correlation between age, weight, presenting body temperature, duration of illness or presenting peripheral parasite density and duration of pruritus. Responses to oral antimalarial drugs were similar in both groups. There was no correlation between indices of therapeutic response and the duration of pruritus. Analysis of the disposition kinetics of parasitaemia and of the hepatomegaly associated with malaria, using a non-compartmental model similar to that used in characterizing drug disposition, showed that the two groups had similar half-lives of parasitaemia (t(1/2 pd)), volumes of blood completely cleared of parasites per unit time (CL(Bpd)) and ratios of parasite-clearance time to t(1/2 pd), and similar values for the corresponding parameters derived from hepatomegaly resolution. There was no apparent relationship between the indices of parasite- or hepatomegaly-disposition kinetics and the duration of pruritus.

Randomized comparison of chloroquine and amodiaquine in the treatment of acute, uncomplicated, Plasmodium falciparum malaria in children

The increasing resistance of Plasmodium falciparum to chloroquine (CQ) has created an urgent need for the evaluation of alternative, effective, safe, cheap, readily available and affordable antimalarial treatments. In the present study, the efficacy of amodiaquine (AQ) in the treatment of acute, symptomatic, uncomplicated, P. falciparum malaria was compared with that of CQ, each drug being given at 10 mg/kg per day for 3 days (days 0, 1 and 2). The 210 subjects (104 given AQ and 106 CQ) were Nigerian children aged 5 months-12 years. Fever-clearance times (FCT), parasite densities on days 1-4 and parasite-clearance times (PCT) were all significantly lower with AQ than with CQ. Mean (S.D.) PCT, for example, were 2.6 (0.8) days with AQ and 3.0 (1.0) days with CQ (P = 0.001). The cure rates obtained on days 14, 21 and 28 - 98.1% v. 79.3% (P =0.000), 97.1% v. 64.2% (P = 0.00001) and 95.2% v. 58.5% (P = 0.0000000) with AQ and CQ, respectively - were all also significantly higher with AQ. All but two of the 20 subjects who were considered CQ-treatment failures by day 14 (i.e. two RIII, two RII and 16 RI) responded to subsequent treatment with AQ, with PCT (but not FCT) significantly shorter than during their initial treatment with CQ. In siblings in whom there was clustering of infections, the cure rates were 100% with AQ (N =12) and 63.6% with CQ (N = 11; P = 0.03). Adverse reactions to CQ and AQ were similar and tolerable: pruritus in 10 and 11 children in the AQ and CQ groups, respectively, and gastro-intestinal disturbances which occurred in three children from each group. Haematological parameters were not adversely affected by either drug. At least in the setting of the present study, AQ appears more effective than CQ, effective against CQ-resistant infections, and well tolerated by children with acute, uncomplicated, P. falciparum malaria. It may therefore be useful as an alternative to CQ in areas of CQ resistance.

Urinary recovery of caffeine and its metabolites in healthy African children

Consumption of caffeine containing products is very popular in African children, particularly during ill health in the belief that caffeine promotes good health. This study aims to define the metabolism of caffeine, which takes place in the liver in a group of healthy Nigerian children. About 100 mg of caffeine was ingested after an overnight fast. Urine was collected before caffeine ingestion and over 12-hour periods for 36 hours in 13 healthy Nigerian children. The percentage of caffeine and metabolites recovered in urine was determined by high performance liquid chromatography. The total urinary caffeine and metabolites recovered over the 36-hour sampling period was 63.6%, with only 0.4% of the caffeine dose ingested recovered as unchanged caffeine during the same period. Insignificant amounts of 3,7-dimethyluric acid (0.2%), 3-methyluric acid (0.3%) and 1,3,7-dimethyluric acid (0.4) were recovered in the 36hour urine sample. This study also found that the N3-demethylation pathway was the principal pathway of caffeine metabolism accounting for 83.3% of the total metabolites recovered while C8-hydroxylation accounted for only 0.6% of metabolites recovered. The pattern of urinary metabolites recovered suggested that N3-demethylation is the principal pathway of caffeine metabolism in healthy African children and that small amounts of unchanged caffeine, as well as 3,7-dimethyluric acid, 3-methyluric acid and 1,3,7-dimethyluric acid were recovered during the sampling period.

Clinical characteristics and disposition kinetics of the hepatomegaly associated with acute, uncomplicated, Plasmodium falciparum malaria in children

The clinical characteristics and the kinetics of the disposition of the hepatomegaly associated with acute, uncomplicated Plasmodium falciparum malaria were investigated in 162 children in an endemic area of Nigeria. Hepatomegaly was significantly more common in the younger than in the older children. Complete resolution occurred in 48% following antimalarial chemotherapy. In the children in whom hepatomegaly did not resolve, a reduction in liver size of < 17% by the time parasitaemia was cleared (usually on day 3) was associated with non-resolution of hepatomegaly by days 7 or 14 of follow-up. An increase in liver size to at least 125% of the baseline value by day 4 or 5 was associated with a lack of therapeutic response, providing the child involved was aged < 5 years. In the children who had complete clearance of parasitaemia and resolution of hepatomegaly, there was no significant relationship between the parasitaemia-derived conventional indices of therapeutic response [i.e. time to clearance of 50% (PC50) or 90% (PC90) of the parasitaemia, and the parasite-clearance time (PCT)] and the corresponding parameters derived from measurement of liver size [i.e. time for resolution of 50% (HR50) or 90% (HR90) of the hepatomegaly and the hepatomegaly-resolution time (HRT)] in the same patients. However, as the HR50:PC50, HR90:PC90 and HRT:PCT ratios were similar (range = 1.6-2.1), the liver parameters may have therapeutic application. In the children with drug-sensitive P. falciparum infections and in whom hepatomegaly completely resolved, the area produced by plotting liver size against time (i.e. the area under the curve of hepatomegaly v. time, or AUChp) increased in proportion to the liver size below the costal margin (P = 0.02, from analysis of variance), but there was no significant difference in the half-lives of hepatomegaly (t1/2hp) or in the ratios of liver size to AUChp, indicating that the kinetics of the resolution of hepatomegaly were linear in the range examined. Comparison of the kinetic indices of hepatomegaly and parasitaemia showed that, although the half-lives of parasitaemia and hepatomegaly and the corresponding clearance values were similar, there was no correlation between these parameters among those in whom hepatomegaly completely resolved and parasitaemia completely cleared. These results indicate that routine clinical measurement of the liver size in children with hepatomegaly during acute, uncomplicated, P. falciparum malaria may have some use in evaluating and monitoring the therapeutic responses of infections. The resolution of hepatomegaly, a reflection of pathological changes, lags behind clearance of parasitaemia in children with P. falciparum malaria, and supports the use of the liver 'rate' as a malariometric index for assessing the intensity of transmission in endemic areas.

Comparative clinical characteristics and response to oral antimalarial therapy of children with and without Plasmodium falciparum hyperparasitaemia in an endemic area

The clinical characteristics and the responses to oral antimalarial therapy of 104 children presenting consecutively with or without Plasmodium falciparum hyperparasitaemia (HP) were investigated in an endemic area. At presentation, although the 52 children with HP were significantly younger and had significantly higher heart rates than the 52 without, there were no significant differences between the two groups in their symptoms or in any other clinical feature of their malaria. Responses to oral antimalarial drugs were similar in both groups. Analysis of the disposition kinetics of parasitaemia, using a non-compartmental model similar to that used in characterizing drug disposition, showed that the two groups had similar half-lives of parasitaemia (t1/2pd), volumes of blood completely cleared of parasites per unit time (CLBpd), and parasite-clearance-time:t1/2pd ratios. Three children in the HP group, all aged < 3 years, progressed to cerebral malaria within 8 h of presentation, and another HP child presented with isolated trunkal ataxia, indicative of cerebellar involvement. No child in the non-HP group had any of the features of severe malaria. Although the clinical characteristics and responses to oral therapy of children with and without HP are therefore very similar, young children with HP appear to have an increased risk of developing other features of severe malaria.

Congenital malaria in a hyperendemic area: a revisit

Screening of 104 mother-baby pairs for P. falciparum malaria revealed that 29% of mothers from low socio-economic group and 11% of their babies had malaria parasitaemia. The corresponding figures for middle and high socio-economic groups were 15% and 7%, respectively. The parasite densities in the babies were not proportional to maternal load and were generally low, although higher in the low socio-economic group. Maternal pyrimethamine prophylaxis did not appear to protect babies from parasitisation and there was no demonstrable beneficial effect on the babies' birtth-weights.

Bioavailability of ciprofloxacin and fleroxacin: results of a preliminary investigation in healthy adult Nigerian male volunteers

The absolute bioavailability (BA) of ciprofloxacin and fleroxacin were evaluated in 19 adult Nigerian male volunteers. Subjects meeting the selection criteria were randomized to receive treatment either with fleroxacin (200 mg-i.v. and 200 mg oral dose) or ciprofloxacin (200 mg-i.v. and 250 mg oral dose). The i.v./oral or oral/i.v. switch was made after a one week washout period. Blood and urine samples were collected at pre-determined time intervals over a 72 h period for analysis of drug levels. Following intravenous administration the maximum serum concentration (Cmax) was 2.7+/-1.06mg/l for ciprofioxacin and 0.99+/-0.41 mg/l for fleroxacin; the area under the blood level curve (AUC) was 8.82+/-3.19 mg x h/l with ciprofloxacin and 8.52+/-3.83 mg x h/l with fleroxacin. Following oral administration the Cmax was 1.52+/-0.94 mg/l with ciprofloxacin and 0.57+/-0.08 mg/l with fleroxacin; the AUC was 9.87+/-4.10 and 7.55+/-1.42 mg x h/l, respectively. The absolute BA following oral administration was found to be 0.79+/-0.47 for ciprofloxacin and 1.01+/-0.78 for fleroxacin. When these BA results were corrected for renal clearance [Cl(r)] and elimination half-life (t1/2) the values were reduced to 0.37+/-0.17 and 0.31+/-0.18, respectively, for ciprofloxacin and 0.53+/-0.23 and 0.99+/-0.38, respectively, for fleroxacin. Only 38% with ciprofloxacin and 59% with fieroxacin, of the administered dose, was excreted unchanged following oral administration. More work, however, needs to be done on ciprofloxacin to support and/or confirm the above findings. Fleroxacin, on the one hand, exhibited a different trend from that observed in the literature with respect to Cmax and AUC where the values observed in this study were 3--4 fold lower than expected following identical doses, whilst on the other hand the observed BA profile in this study was consistent with literature trends.

Arginine vasopressin secretion in Kenyan children with severe malaria

Hyponatraemia is common in African children with severe malaria, but the cause is unknown. We measured plasma sodium (p[Na]) and arginine vasopressin concentrations (p[AVP]) in 30 consecutive children with severe malaria (19 had cerebral malaria), on admission, at 48 and 96 h after admission. Hyponatraemia (p[Na] < 130 mmol/l) occurred in 53 per cent of the children and was unrelated to peripheral parasite density, dehydration or abnormal renal function. The highest p[AVP] were seen in patients with cerebral malaria. Overall, p[AVP] declined 96 h after treatment. In children with hyponatraemia (cerebral and non-cerebral), p[AVP] levels were not suppressed and in 67 per cent of cases they were deemed inappropriate. Inappropriate AVP secretion is common in children with severe malaria and may influence fluid therapy after correction of initial dehydration.

The effects of acute falciparum malaria on the disposition of caffeine and the comparison of saliva and plasma-derived pharmacokinetic parameters in adult Nigerians

OBJECTIVES

The pharmacokinetics of caffeine and its dimethylxanthine metabolites were evaluated in Nigerians, for whom it is normal to consume caffeine-containing beverages during ill health and recuperation in the belief that caffeine aids early recovery from illness; however, there are no data defining the kinetics of caffeine in healthy and ill Nigerians.

MATERIALS AND METHODS

A single oral dose of 300 mg caffeine was given to ten healthy adult Nigerians and ten adults suffering from acute uncomplicated Plasmodium falciparum malaria infection. Caffeine and its dimethylxanthine metabolites were measured in plasma and saliva of healthy subjects and in plasma of patients suffering from malaria using high-performance liquid chromatography.

RESULTS

The plasma pharmacokinetics of caffeine per se in both groups was similar (P > 0.05). The maximum plasma concentration (Cmax) of paraxanthine was significantly lower (P < 0.05) in malaria (0.9 +/- 0.4 microg/ ml) than in healthy controls (1.4 +/- 0.5 microg/ml), and the paraxanthine:caffeine area under the plasma concentration time curve ratio, an index of cytochrome P450 (CYP)IA2 activity was significantly lower (P < 0.05) in malaria patients (0.5 +/- 0.1) than in healthy controls (0.3 +/- 0.2). The elimination half-life of theophylline was longer in malaria, while the area under the plasma concentration time curve of theobromine was significantly higher (P < 0.05) in malaria (7.1 +/- 3.4 microg ml(-1) h) than in healthy adults (4.1 +/- 2.2 microg ml(-1) h). Excellent correlations were found between saliva and plasma concentrations of caffeine (r2 = 0.98) with a mean saliva:plasma concentrations ratio of 0.7 +/- 0.1. The plasma concentrations (Cmax and AUC) were therefore higher than the corresponding salivary levels, so that the apparent oral clearance calculated for saliva exceeded the true oral clearance based on plasma data.

CONCLUSIONS

Acute Plasmodium falciparum malaria produced significant changes in the disposition of caffeine metabolites. Analysis of concentrations in saliva is a useful non-invasive method for monitoring the kinetics of caffeine and paraxanthine in Nigerians.

The pharmacokinetics of caffeine in Nigerian children suffering from malaria and kwashiorkor

OBJECTIVES

Caffeine-containing beverages are generally consumed by Nigerians suffering from malaria and kwashiorkor in the belief that caffeine aids early recovery from these illnesses, which are common in the tropics. However, there are no studies on the influence of these diseases on the absorption and pharmacokinetics of caffeine in Africans.

MATERIALS AND METHODS

A single oral dose of caffeine was given to five healthy children and to five and seven children suffering from malaria and kwashiorkor, respectively. Caffeine and its dimethylxanthine metabolites were measured in plasma using high-performance liquid chromatography.

RESULTS

The maximum plasma concentration (Cmax) of caffeine and the time of Cmax were similar (P > 0.05) in the three groups. However, the elimination half-life of caffeine was significantly longer in children with malaria (9.2 +/- 3.5 h) (P < 0.01) and kwashiorkor (13.1 +/- 7.9 h) (P < 0.05) than in the healthy controls (3.7 +/- 1.8 h). The total plasma oral clearance of caffeine of 4.4 +/- 1.9 ml/min/kg in healthy children was significantly higher (P < 0.01) than in those with kwashiorkor (2.0 +/- 0.9 ml/min/kg) and malaria (1.6 +/- 1.0 ml/min/ kg) (P < 0.05). Paraxanthine was the principal metabolite in all the three groups with Cmax significantly higher in healthy children (1.3 +/- 0.3 microg/ml) than in children with malaria (0.8 +/- 0.4 microg/ml) (P < 0.05) and kwashiorkor (0.3 +/- 0.1 microg/ml) (P < 0.0001). CYP1A2 activity, measured by the plasma ratios of paraxanthine: caffeine, was significantly lower in kwashiorkor and malaria.

CONCLUSIONS

This study showed that the plasma kinetics of caffeine are significantly altered in malaria and kwashiorkor, and CYP1A2 activity was lower in these two disease groups.

Comparative efficacy of chloroquine plus chlorpheniramine alone and in a sequential combination with sulfadoxine-pyrimethamine, for the treatment of acute, uncomplicated, falciparum malaria in children

One hundred and eight children with acute, symptomatic, uncomplicated, falciparum malaria were randomized to receive chloroquine (for 3 days) plus chlorpheniramine alone (for seven days) (CQ-CP group; N = 55) or, in a sequential treatment, chloroquine plus chlorpheniramine for 3 days followed, on the fourth day, by a single oral dose of sulfadoxine-pyrimethamine (25 mg sulfadoxine/kg) (CQ-CP-SP group; N = 53). The mean (S.D.) parasite-clearance time in the CQ-CP group [2.1 (0.7) days; range = 1-5 days] was similar to that in the CQ-CP-SP [2.1 (0.8) days; range = 1-5 days]. The fever-clearance times were also similar: 1.2 (0.1) days (range = 1-3 days) v. 1.1 (0.4) days (range = 1-3 days). The cure rates on days 14, 21 and 28 were 98.2%, 96.3% and 92.7%, respectively in the CQ-CP group, and 100%, 100% and 96.2%, respectively, in the CQ-CP-SP group. The rates of gametocyte carriage were low and similar (5.4% in the CQ-CP group and 3.8% in the CQ-CP-SP group) throughout the duration of the study. Both treatment regimens were relatively well tolerated, the main adverse reactions being similar: sleepiness (on day 1) and pruritus (on days 1-3). No adverse effect was attributable to SP. The results indicate that sequential treatment, for 3 days with CQ and CP, followed by a single dose of SP, is effective and well tolerated in children with acute, uncomplicated, falciparum malaria and may be an alternative treatment for CQ- and/or SP-resistant falciparum malaria. Treatment with a CQ-CP combination (CQ and CP for 3 days and then CP alone for another 4 days) is also effective but requires continuing administration after the signs and symptoms of acute malaria have disappeared.

Gastrointestinal manifestations of acute falciparum malaria in children

The gastrointestinal manifestations of acute symptomatic uncomplicated falciparum malaria were studied in 184 consecutive children aged from 6 months to 15 years. Vomiting was the most common and epigastralgia the least common presenting symptom. Peripheral parasite density was higher in children who were vomiting than in those who were not. There was no relationship between the density of peripheral parasitaemia and the duration of gastrointestinal symptoms at presentation. All gastrointestinal symptoms cleared within 3 days after instituting antimalarial therapy.

Comparative cardiac effects of halofantrine and chloroquine plus chlorpheniramine in children with acute uncomplicated falciparum malaria

The cardiac effects of halofantrine (HF) and chloroquine plus chlorpheniramine (CQ-CP), a histamine H1 antagonist which reverses chloroquine insensitivity in Plasmodium falciparum in vitro and in vivo, were assessed in 41 children with acute symptomatic uncomplicated P. falciparum malaria by electrocardiographic and clinical monitoring over a period of 14 days. In addition, the cardiac effects of chloroquine (CQ) alone and CQ-CP were compared in 10 age- and sex-matched children. HF produced a significantly higher proportion of abnormally prolonged P-R interval (8 abnormally prolonged out of 132 total P-R events) than CQ-CP (1 of 133 P-R events) (P = 0.03), but a similar proportion of prolonged Q-Tc interval to that of CQ-CP (46 of 149 versus 29 of 134 events, P = 0.07). Compared with pre-treatment Q-Tc, HF significantly prolonged this interval from 6 to 96 h post treatment with a maximum effect at 24 h after commencing HF treatment. CQ-CP by contrast produced significant changes in Q-Tc values from 6 to only 48 h with a maximum effect at 48 h. HF-induced Q-Tc prolongations were significantly higher than those of CQ-CP only at 24 h. The cardiac effects of CQ-CP were similar to those of CQ alone. Despite the electrocardiogram abnormalities, rhythm disturbance was rare and there was no clinical symptom in any of the treatment groups. Compared with HF, CQ-CP produced cardiac effects that were less severe and in fewer children with acute falciparum malaria. The addition of CP to CQ does not significantly amplify the cardiac effects of CQ in children with acute uncomplicated falciparum malaria.

Single-dose pharmacokinetic study of ciprofloxacin and fleroxacin in healthy adult Nigerian volunteers

The kinetics of absorption, distribution and elimination of ciprofloxacin and fleroxacin (following an intravenous dose of 200 mg), were evaluated in 24 adult healthy male Nigerian volunteers. Appropriate mathematical models were applied with the aid of a microcomputer software program for the estimation of the basic pharmacokinetic parameters. Appropriate statistical tests and profiles formed the basis for accepting or rejecting a proposed model. For parametric comparisons between the profile of the two drugs, the null hypothesis of no difference in their pharmacokinetic profile was proposed. All statistical tests were performed at a significance level of 95% (alpha = 0.05) and the 95% confidence level was determined where appropriate. Additionally, the model-independent or stochastic method of analysis was also employed in the pharmacokinetic evaluation of the blood level data. The parametric estimates obtained from both methods were compared. The plasma elimination half-life (t1/2) was estimated as 13.8 +/- 5.5 h for fleroxacin and 7.5 +/- 4.0 h for ciprofloxacin; the maximal plasma concentration (Cmax) was 0.8 +/- 0.3 and 2.3 +/- 1.0 mg/l for fleroxacin and ciprofloxacin, respectively, whilst the volume of distribution (Vd) was 2.5 +/- 1.6 and 0.4 +/- 0.3 liters/kg for fleroxacin and ciprofloxacin, respectively. 71 and 70% of unchanged drug were excreted in urine for fleroxacin and ciprofloxacin, respectively. With respect to comparative values, the results confirmed trends already observed in the literature, particularly as regards the t1/2. However, for fleroxacin there was a significant deviation from the literature trends with respect to Vd, Cmax and AUC. The results also confirmed earlier findings, advocating a once-daily dosage schedule for fleroxacin also in the Negroid population.

Cardiac effects of halofantrine in children suffering from acute uncomplicated falciparum malaria

The cardiac effects of halofantrine were assessed in 42 children with acute symptomatic uncomplicated Plasmodium falciparum malaria by electrocardiographic (ECG) and clinical monitoring over a period of 14 d. The children were treated with oral halofantrine 8 mg/kg body weight every 6 h for 3 doses. There was significant prolongation of the P-R interval (compared with the pre-treatment value) only at 8 h after drug administration. However, first degree auriculoventricular (AV) block occurred in 2 children at 8 h or 8 and 48 h, and second degree AV block in another child at 48 h. There was significant prolongation of the Q-Tc interval at 8, 16, 24, 48 and 72 h after treatment; the proportions of children with Q-Tc interval > 0.44 s were also significantly higher at all these times except 72 h. Rhythm disturbance was rare. There was no significant ECG change at 168 or 336 h. Despite the ECG abnormalities, there was no clinical symptom. These findings indicate that, in children, the currently recommended dose of halofantrine for the treatment of falciparum malaria may produce serious cardiac side effects.

Comparative efficacy of chloroquine plus chlorpheniramine and halofantrine in acute uncomplicated falciparum malaria in Nigerian children

In the face of growing chloroquine resistance of Plasmodium falciparum, efforts to prolong the clinical usefulness of the drug have partly concentrated on its combination with potential resistance-reversing compounds. However, clinical studies on such combinations have been limited. We have compared the efficacy of halofantrine, an arylaminoalcohol effective in chloroquine resistant malaria, and a combination of chloroquine plus chlorpheniramine, a histamine H1 receptor antagonist which reverses chloroquine resistance of P. falciparum in vitro and in vivo, in 100 children with acute symptomatic uncomplicated falciparum malaria in an area in Nigeria where the rate of chloroquine resistance is 35-45%. Both chloroquine plus chlorpheniramine and halofantrine produced similar parasite and fever clearance times and cure rates (96%). Both treatment regimens were relatively well tolerated. Pruritus was commoner in patients treated with chloroquine plus chlorpheniramine than in those treated with halofantrine. Intravascular haemolysis occurred in one patient, and abdominal pain with or without diarrhoea occurred in 4 patients, treated with halofantrine. In vitro, the chloroquine resistance of P. falciparum isolates obtained from the patients was reversed by verapamil. All patients with isolates which were chloroquine-resistant in vitro were cured by either therapy. These results indicate that chloroquine plus chlorpheniramine is as effective as halofantrine and is without overt deleterious effect in treating acute uncomplicated chloroquine-resistant falciparum malaria in children, and may be a clinically useful alternative for this purpose in Nigeria.

Pharmacokinetics of quinine in African patients with acute falciparum malaria

The pharmacokinetics of quinine were studied in six Nigerian patients during acute uncomplicated falciparum malaria and convalescent periods. An oral dose of 10 mg/kg quinine dihydrochloride administered 8-hourly for 7 days gave parasite and fever clearance times of 36.0 +/- 16.6 h and 18.0 +/- 6.4 h, respectively. From the individual quinine plasma profiles the mean plasma concentration of quinine at the time of parasite clearance was estimated as 4.5 +/- 1.1 micrograms/ml. Plasma quinine levels during malaria rose rapidly reaching a peak around the second and third days and declining thereafter as patients improved clinically. In acute malaria plasma quinine levels were more than two-fold higher than in convalescence; the mean AUC(0-12) in malaria was 37.9 +/- 14.7 micrograms.h/ml compared to 17.9 +/- 8.5 micrograms.h/ml in convalescence. The apparent oral clearance (CL/F) and volume of distribution (Vd/F) during the acute phase of the malaria (1.9 +/- 0.7 ml/min/kg and 1.8 +/- 0.9 l/kg, respectively) were significantly lower than in convalescence (4.5 +/- 2.1 ml/min/kg and 4.2 +/- 3.2 l/kg). The present data suggest that malaria parasites in African patients are still very sensitive to quinine and that the current dosage of quinine is effective for the treatment of acute falciparum malaria in African patients without augmenting therapy with any other drug such as tetracycline or sulphadoxine-pyrimethamine. It also confirms that malaria significantly alters the pharmacokinetics of quinine in humans.

In vitro and in vivo reversal of chloroquine resistance in Plasmodium falciparum with promethazine

The effect of combining promethazine with chloroquine was examined against Plasmodium falciparum in vitro in the Aotus-P. falciparum model and in bioassays from volunteers given promethazine. The combination of chloroquine plus promethazine (1 x 10(-6) M) reversed chloroquine resistance in standard P. falciparum clones and patient parasite isolates from Nigeria. The combination reduced the 50% inhibitory concentrations (IC50s) for chloroquine against resistant parasites by 32-92%. Coadministration of promethazine with chloroquine also demonstrated a dose-dependent effect in Aotus monkeys infected with chloroquine-resistant P. falciparum. Monkeys were given a chloroquine dose (20 mg/kg of body weight for seven days), which normally has no effect on parasitemia, plus 10, 20, 40, or 80 mg of promethazine/kg of body weight. In one monkey, parasitemia was suppressed at the lowest promethazine dose, but re-treatment with 20 mg/kg resulted in clearance of parasitemia. Initial treatment with chloroquine and 20 or 40 mg/kg of promethazine cleared parasitemia in some animals followed by recrudescence. Re-treatment at higher doses cured one monkey and resulted in initial clearance and delayed recrudescence 28 or 63 days after treatment in two monkeys. Recrudescent parasitemia in the two monkeys was low (10 parasites/microl of blood) and subsequently cleared without re-treatment. An in vitro bioassay model was developed to examine the effects of clinically achievable doses of promethazine on parasites susceptibilities in vitro. Plasma samples taken at hourly intervals from patients given a single oral dose of 25 mg of promethazine decreased the IC50 values for chloroquine by 20-58% with the most significant reductions occurring in plasma obtained from volunteers 3-4 hr after ingestion. Plasma obtained from two volunteers 6 hr after ingestion of the drug demonstrated no effect on chloroquine susceptibility, suggesting that study of the pharmacokinetic disposition and potential interaction is warranted to optimize the dose regimen in patients for antimalarial efficacy. Historic use of this drug combination for treatment or prevention of chloroquine-associated pruritus or as an antiemetic suggest that the combination is safe and effective when used at standard dosages. The results from this study demonstrate that promethazine is a potent modulator of chloroquine resistance. Clinical evaluation of therapeutic regimens is required to validate clinical efficacy of this promising combination for treatment of uncomplicated chloroquine-resistant malaria.