In vivo and in vitro responses to quinine and quinidine of Plasmodium falciparum*

Bulletin of the World Health Organization, 66 (3): 347-352 (1988) © World Health Organization 1988 In vivo and in vitro responses to quinine and quinidine of Plasmodium falciparum* A. SABCHAREON,' T. CHONGSUPHAJAISIDDHI,2 V. SINHASIVANON,3 P. CHANTHAVANICH,4 & P. ArrANATH5 A total of66 Thai children with uncomplicatedfalciparum malaria were treated orally with regimens ofeither quinine or quinidine. Radical cures were observed in 85% (28 of33) of the children who received quinine and in 88% (29 out of 33) of those who received quinidine. Treatment failures in both groups were RI responses. 7he mean trough level of quinidine (10 pimol/l) was about 2.5-times less than that of quinine (25 umol/l). The electrocardiograms of the two treatment groups differed significantly in that there was an acuteprolongation ofthe QTc interval in 56% ofthose who received quinidine compared with 21.0% ofthose given quinine. In vitro assays ofthe pre- treatment drug susceptibilities ofthe isolates ofPlasmodium falciparum indicated that the mean minimum inhibitory concentration (MIC) for quinidine (1.44 ,umol/l) was about half that for quinine (3.02 pamol/l). Although both drugs are equally effective, quinine is recommendedfor treatment ofmultidrug-resistant malaria inpaediatricpatients, primarily because of the cardiac effects produced by quinidine. Since about 1981 there has been a significant decline in the effectiveness of quinine for the treat- ment of chloroquine-resistant falciparum malaria in Thailand (1). In vitro studies (1-3) have revealed that this is related to a corresponding decrease in the innate susceptibility of Plasmodium falciparum strains to quinine. Although the combination quin- ine-tetracycline has remained highly effective for treatment of falciparum malaria in adults (4, 5), extended administration of tetracyclines to young children is generally contraindicated (6). Treatment of multiresistant falciparum infections in paediatric patients has become a significant problem. We have recently reported, however, that a single dose of mefloquine (17-29 mg base per kg body weight) is highly effective in treating falciparum malaria among children aged 5-12 years (cure rate, 97.5%) (7). In order to prevent the emergence of mefloquine-resist- ant parasites, use of the drug has been restricted for * From the Department of Tropical Paediatrics, Hospital for Tropical Diseases, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand. Requests for reprints should be sent to Dr Sabchareon at this address. 1 Associate Professor. 2 Professor and Head. 3 Lecturer. 4 Assistant Professor. 5 Head, Research Laboratory. the treatment of patients with microscopically diag- nosed falciparum malaria and is available only in malaria clinics and a few hospitals in Thailand (S. Pinichpongse, personal communications, 1986 and 1987). Use of regimens of quinine that extend over at least 7 or 8 days are both safe and effective for paediatric patients (1). Recently, quinidine has been recommen- ded as an alternative treatment for falciparum malaria in adults (8, 9); however, its efficacy in paediatric patients has not been evaluated. The present study was therefore undertaken to compare the efficacy of quinine and quinidine in treating children with multi- drug-resistant falciparum malaria, and to evaluate possible mechanisms of treatment failures by mon- itoring serum drug levels during treatment and by assaying the in vitro drug susceptibility of P. falci- parum strains to quinine and quinidine. MATERIALS AND METHODS Patients A prospective, randomized trial involving 72 chil- dren with uncomplicated falciparum malaria was conducted from July 1984 to January 1985. Parents of all the children gave informed consent for partici- 4887 347- 348 A. SABCHAREON ET AL. Table 1. Mean body temperature, erythrocyte volume fraction, and parasite count in 66 Thai children in the study with falciparum malaria Sex Geometric mean parasite count Drug No. of children Male Female Mean temperature (OC)a Mean EVFb (per jA) Quinine 33 19 14 39.0 0.26 14200 (38.0-40.6) c (0.12-0.36) (800-97 400) Quinidine 33 18 15 39.1 0.26 14800 (37.6-45.0) (0.13-0.38) (700-94300) Measured orally. b EVF - erythrocyte volume fraction. ' Figures in parentheses are the range. pation in the study. The patients were all Thai and were mainly from the south-eastern region of the country, near the Thai-Kampuchean border. The children's ages ranged from 2 to 12 years (mean, 6.7 years). Diagnosis of P. falciparum infection was based on clinical signs and symptoms and confirmed by microscopic examination of Giemsa-stained thick and thin blood films. The children exhibited asexual parasitaemia levels of 700-97 400 parasites per gl(Table 1), and urine samples from all the patients were negative for 4-aminoquinolines in the Dill- Glazko test (10) and for sulfonamides in the lignin test (11). All the children were admitted to the Hospital for Tropical Diseases, Bangkok, for treat- ment and observation for 28 days, and of the 72 originally included in the study, 66 (92 %) completed the full 28-day follow-up period. Laboratory studies Samples of blood were taken from each child and the haemoglobin concentration, erythrocyte volume fraction, differential leukocyte count, as well as the bilirubin, albumin, globulin, alkaline phosphatase, transaminase, cholesterol, urea nitrogen, and creati- nine levels determined. Urine was tested for albumin, sugar, and bilirubin levels, as well as for the presence of sediments. All laboratory tests were conducted on the day after the child had been admitted to the hos- pital and then weekly for 4 weeks after initiation of drug administration. No significant or unusual lab- oratory finding was noted for the children during the study. Asexual parasites were counted every 12 hours during parasitaemia and then daily for the remainder of the study. Drug regimens An extended 8-day course of quinine, which has been recommended for the treatment of quinine-re- sistant falciparum malaria in paediatric patients (1), was administered to 33 of the children. Quinine sulphatea was given as 10 mg base per kg body weight every 8 hours for 4 days and the dose in- creased to 15 mg base per kg every 8 hours for the next 4 days. Quinidine sulphateb was administered as 10 mg base per kg every 8 hours for 7 days to a sec- ond group of 33 children. Since this study was the first evaluation of the efficacy of quinidine for the treatment of falciparum malaria in children, the same dosage schedule as quinine was not used in order to avoid any possible cardiotoxic effects. Patients were randomly assigned to quinine or quinidine regimens, and medications were given orally as crushed pills. Electrocardiograms (ECGs) were recorded daily, on day 2 and day 1, as well as 2 hours after the morning dose from day 0 to day 7 of the study. One child had abnormal prolongation of the corrected QT interval (QTc) before drug admin- istration, and the ECG records of this patient were excluded from the study. The results of the treatments were categorized as S (clearance within 7 days, with- out subsequent recrudescence) or RI (clearance of asexual parasitaemia, followed by recrudescence) according to the grades of resistance defined byWHO (12). There were no RII (marked reduction ofasexual parasitaemia but no clearance) or RHII (no marked reduction of asexual parasitaemia) responses to either the quinine or quinidine regimens. Blood drug levels Plasma quinine or quinidine levels were deter- mined prior to administration of the first dose of the drug, 4 hours following its administration, and then daily before the morning dose throughout the course of the treatment. The level in plasma of quinine or a Thai Government Pharmaceutical Organisation. b Labatec, Pharma S.A., Geneva, Switzerland. RESPONSE OF PLASMODIUM FALCIPARUM TO QUININE AND QUINIDINE quinidine was determined using the method reported by Cramer & Isaksson (13). Pre-administration drug plasma levels represented the trough values and those 4 hours after administration the peak plasma level on day 0. In vitro assays Prior to treatment, the in vitro susceptibility of isolates of P. falciparum to quinine, quinidine, chloroquine, and mefloquine was determined using the standardized procedure recommended by WHO (12, 14). The minimum inhibitory concentration (MIC) was defined as the lowest concentration that completely inhibited schizont formation. 20 Quinine _ 15- 5 / / ~~~~~~~~~~'~I[Quinidine Z 0 I R. 0 1 2 3 4 5 6 7 8 Day of treatment Fig. 1. Mean plasma trough levels of quinine, and quinidine in children in the study (vertical bars represent the standard error of the mean). RESULTS In vivo responses There were no apparent differences in the response of the P. falciparum infections to either the 8-day course of quinine or the 7-day course of quinidine, and both drugs appeared equally effective as anti- malarials. The mean fever clearance times (47.6 hours for quinine and 51.6 hours for quinidine) and the parasite clearance times (98.8 hours for quinine and 94.5 hours for quinidine) for both regimens were comparable. Recrudescences occurred between day 21 and day 27 in five (15%) of the patients treated with quinine and between day 17 and day 21 in four Table 2. Frequencies of prolonged QTc and PR intervals among Thai children with falciparum malaria who were treated with quinine or quinidine in the study Quinine Quinidine No. with No. with No. with No. with Day of prolonged prolonged prolonged prolonged treatment QTc PR QTc PR 0 0 0 0 0 1 1 3 4 4 2 1 5 8 8 3 0 6 11 14 4 2 9 5 11 5 3 6 7 11 6 4 14 7 10 7 2 13 4 9 Total 13 56 46 67 (12%) of those who received quinidine. All treatment failures were RI responses. The clinical side-effects included transient and generally mild nausea. Tin- nitus and dizziness were reported by older children on both quinine and quinidine regimens. Electrocardiogram effects Electrocardiogram effects occurred among patients in both the quinine and quinidine groups (Table 2). Some of those treated with quinine exhibited a sig- nificant acute prolongation of the QT, (8 patients) and a significant prolongation of the PR intervals (16 patients) compared with pre-treatment baseline values. Acute prolongation of the QT, (19 patients) and PR intervals (27 patients) was also noted among children treated with quinidine. The prolonged QT, interval was significant (P<0.O1, x2 test) in more patients of the quinidine group (55.9%) than in those of the quinine group (21%). Moreover, the fre- quency of prolonged QT, intervals among patients treated with quinidine was 3.5-times greater than among those who received quinine. The frequencies ofprolonged PR intervals in the two treatment groups were similar. During the afebrile periods from day 3 to day 8 of the study, sinus arrhythmias were noted among 10 patients in the quinine group and among seven in the quinidine group. Plasma quinine and quinidine levels The levels of quinidine in plasma were generally about 2.5-times lower than those of quinine, although 349 A. SABCHAREON ET AL. Table 3. Minimum in vitro inhibitory concentrations for quinine, quinidine, chloroquine, or mefloquine for Plas- modium faciparum isolates from children in the study Minimum inhibitory concentration (umol/1) Quinine Quinidine Chloroquine Mefloquine (n - 64) (n = 64) (n - 64) (n - 44) Mean 3.02 1.44 3.10 0.124 Standard deviation 1.48 1.05 2.31 0.075 Range 0.32-5.12 0.16-5.12 0.31-10.2 0.04-0.64 Median 2.56 1.28 2.65 0.08 equivalent doses of the two drugs were administered during the first 4 days of therapy (Fig. 1). There were no apparent differences in the plasma levels ofthe two drugs for treatment successes and failures. In vitro responses The in vitro susceptibility of64 of the 66 isolates of P. falciparum to quinine, quinidine, or chloroquine as well as that of44 to mefloquine are shown in Table 3. Based on these results, the parasites were resistant to chloroquine and generally susceptible to meflo- quine. The mean value of the MIC for chloroquine was 3.10 ,gmol/l, while that for mefloquine was 0.124 ltmol/l. All of the MICs for chloroquine were greater than the level that has been defined as indicating resistance to the drug (0.16 pmol/l), while for meflo- quine four (9.1 %) of the MICs were 0.64 iLmol/l. The MICs for quinine (mean, 3.02 ytmol/l) were significantly greater (P< 0.05, Student's t-test) (Table 3). There were no apparent differences be- tween the in vitro patterns of drug sensitivity to quinine or quinidine for patients who were eventually treatment failures compared with those who were treated successfully. Also, for either group there were no differences between the isolates collected before treatment and following treatment failure. DISCUSSION Over the past 5-6 years the efficacy of quinine for the treatment of falciparum malaria in Thailand has diminished significantly. The following two alterna- tive approaches have been recently evaluated: ex- tending the therapy with quinine to 8 days with an increased dose on days 4-7; and substituting quini- dine for quinine (1, 8). Although there were no significant differences in the antimalarial efficacies of either quinine (28 out of 33 (84.8%) cures) or quinidine (29 out of 33 (87.9%) cures) for paediatric patients who followed compar- able dosage schedules, the following two interactive factors may have contributed to the small number of treatment failures with these drugs: achieving and maintaining an adequate drug plasma level; and the innate drug susceptibilities of the parasites. Both these factors were similar for quinine and quinidine. Plasma levels of quinine (25 limol/l) were signifi- cantly higher than those of quinidine (10 ,mol/l), and the in vitro susceptibility of the parasites to quinine (MIC, 3.02 limol/l) was significantly lower than that to quinidine (MIC, 1.44 zmol/l). Variations in either of these factors or their interaction in an individual patient could be significant for the successful out- come of treatment of infection caused by multidrug- resistant strains of P. falciparum, which have only recently developed resistance to quinine. We have reported in a recent study that the ratio of the concentration of quinidine in red blood cells to that in plasma was 1:1.5, whereas the concentration of quinine was significantly lower in red blood cells than in plasma (15). In addition to the low MIC values for quinidine, the relatively high concentration of the drug in red blood cells may be a major factor in explaining its high efficacy. The significant prolongation of QTc and PR inter- vals we have reported indicates that these effects are quinine- and quinidine-related. The sinus arrhyth- mias previously observed before administration of antimalarials in 3 out of 120 (2.5%) children with symptomatic falciparum malaria (16), but in 17 out of 72 (23.6%) children during the therapy with quinine or quinidine (afebrile periods) in the present study suggest that the arrhythmias we observed were drug-related. Although Chongsuphajaisiddhi et al. (7) reported that there was no abnormal prolongation of QT, and PR intervals for patients treated with mefloquine, the frequency of mefloquine-related reversible sinus arrhythmias that they reported (68%) is three times greater than the level we observed for patients treated with quinine or quiidine. In conclusion, it can be stated that for treatment of multidrug-resistant falciparum malaria in paediatric patients, an 8-day course of quinine provides high cure rates and is associated with minimal serious side- effects; nevertheless, in many areas where quinine is not readily available, a 7-day course of quinidine can be used as an alternative therapy provided the patients are closely monitored for possible cardiovascular effects. 350 RESPONSE OF PLASMODIUM FALCIPARUM TO QUININE AND QUINIDINE ACKNOWLEDGEMENTS We are grateful to Dr W. H. Wernsdorfer for his valuable contributions to the study and to Dr G. E. Childs for reviewing the manuscript. The study was supported by grants from the Faculty of Tropical Medicine, Mahidol University, Thailand. WHO's Malaria Action Programme and the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases are thanked for providing supplies. RESUME RtPONSE 7V VIVO ET IN VITRO DE PL4SMODIUM FALCIPARUM A LA QUININE ET A LA QUINIDINE Une etude a et6 entreprise pour comparer le resultat du traitement du paludisme a falciparum par la quinine et la quinidine chez des enfants thailandais et pour evaluer l'influence eventuelle de la concentration serique du medi- cament et de la chimiosensibilite du parasite sur les echecs therapeutiques. Cette etude, qui s'est deroulee de juillet 1984 a janvier 1985, a porte sur 72 enfants atteints de palu- disme a falciparum non complique chez lesquels le nombre de parasites asexues par microlitre de sang variait entre 700 et 97 400. Tous les enfants ont ete admis a l'H6pital des Maladies tropicales de Bangkok pendant la dur&e du traite- ment. Soixante-six d'entre eux ont ete suivis pendant toute la periode d'observation de 28 jours. Les enfants ont ete repartis au hasard en deux groupes de 33 sujets qui ont ete traites, l'un avec la quinine, l'autre avec la quinidine. Le premier groupe a recu du sulfate de quinine par voie orale a raison de 10 mg de base par kg de poids corporel toutes les 8 heures pendant 4 jours, dose qui a 6te portee a 15 mg pendant les 4 jours suivants. Le deuxieme groupe a recu du sulfate de quinidine par voie orale a raison de 10 mg de base par kg de poids corporel toutes les 8 heures pendant 7 jours. Un electrocardiogramme (ECG) a ete realise une fois par jour, l'avant-veille et la veille de l'administration du medicament, puis deux heures apres la premiere dose de la journee du jour 0 au jour 7. Chez un des enfants, on a note un allongement significatif des intervalles QT corriges (QTc) avant l'instauration du traitement et les ECG de cet enfant ont ete exclus. Les concentrations plasmatiques de quinine et de quini- dine ont ete mesurees avant l'administration de la premiere dose de medicament, 4 heures apres celle-ci, et ensuite quotidiennement, avant la premiere dose de la journee, pendant toute la duree du traitement. Sur les 66 isolements de Plasmodium falciparum re- cueillis avant le traitement, 64 ont ete soumis a des essais de sensibilite a la quinine, a la quinidine et i la chloroquine, tandis que 44 etaient egalement soumis a un essai de sensi- bilite a la mefloquine. Tous ces essais ont ete effectues selon la methode recommand6e par l'OMS. L'etude a montre que la quinine et la quinidine avaient une efficacite equivalente et que le temps necessaire a la dis- parition de la fi6vre et de la parasitemie etait comparable pour les deux medicaments. Le taux de guerison a ete de 85% avec la quinine et de 88% avec la quinidine. Dans tous les cas olt il y a eu echec du traitement, on a observe une reponse RI. Parmi les effets secondaires, on a note des naus&es legeres et transitoires, des bourdonnements d'oreille et des vertiges. Un allongement important de l'intervalle QT corrige (QTc) a ete note chez un pourcentage significativement plus eleve (P<0,001) d'enfants traites a la quinidine (56%) que d'enfants traites a la quinine (21 %). Par contre, il n'y a pas eu de difference significative entre les deux groupes en ce qui concerne l'aljongement des intervalles PR. Pendant les periodes afebriles, du jour 3 au jour 8, on a note des arythmies sinusales chez 10 des enfants traites avec la quinine et chez 7 de ceux qui avaient recu de la quinidine. Les minimums de concentration serique ont ete environ 2,5 fois plus faibles pour la quinidine que pour la quinine, mais on n'a pas observe de difference dans le profil de concentrations seriques entre les patients gueris et ceux chez lesquels le traitement a echoue. En ce qui concerne la reponse in vitro, la concentration minimale inhibitrice (CMI) a ete environ deux fois plus faible pour la quinidine que pour la quinine (P< 0,05). La pharmacosensibilite des parasites isoles chez les patients traites soit avec la quinine, soit avec la quinidine, n'a pas presente de difference signi- ficative. De meme, il n'y a pas eu de difference de CMI entre les isolements de P. falciparum recueillis dans chaque groupe avant traitement et apres echec du traitement. Dans tous les cas, la CMI de chloroquine depassait de 0,16 jsmol/l la concentration a partir de laquelle on considere qu'il y a chloroquinoresistance. La plupart des isolements se sont montres sensibles a la mefloquine, mais pour 4 d'entre eux (9%) la CMI de cette substance a ete de 0,64 ismol/l. 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