Intramuscular loading dose of quinine for falciparum malaria: pharmacokinetics and toxicity

The treatment of falciparum malaria

Effective treatment for falciparum malaria has been available for over 300 years, and for most of this time physicians have argued over the best doses and the methods of administering antimalarial drugs. A reasonable consensus has since emerged on the treatment of uncomplicated malaria, but there is still disagreement over the management of severe infections, and as a consequence there have been confusing and dangerous discrepancies in treatment recommendations. In this review, Nicholas White discusses the confusion, offering a rational basis for the clinical treatment of both uncomplicated and severe falciparum malaria.

[Treatment of cerebral malaria in African children by intravenous quinine: comparison of a loading dose regimen to a regimen without a loading dose]

OBJECTIVE

To compare in a randomized study the efficacy and the toxicity of the new WHO intravenous quinine treatment of cerebral malaria including a loading dose regimen to a regimen without loading dose.

PATIENTS AND METHODS

Seventy-two children eight months to 15 years of age with cerebral malaria were included. Quinine formiate was administered to a group of 35 patients in an initial loading dose of 20 mg salt/kg (equivalent to 17.5 mg/kg of the base) in 10 mL/kg of 5% glucose over four hours, followed eight hours later by a maintenance dose quinine of 10 mg salt/kg (equivalent to 8.7 mg/kg of the base) dissolved in 15 mL/kg of 5% glucose over and every 12 hours. The second group of 37 patients received intravenous quinine 15 mg salt/kg (13.1 mg of base) dissolved in 15 mL/kg of 5% glucose infused over 6 to 8 hours, every 12 hours. In both groups this treatment was continued until the patient could swallow, then quinine tablets were given to complete seven days treatment. The assessment of cardiovascular side effects was made by an ECG at admission, the 4th hour, the 24th hour and at the end of treatment for each patient.

RESULTS

Coma mean durations were similar in the two groups: 35.5 +/- 17.8 hours and 28.6 +/- 14.4 hours respectively for the loading dose group and the group without loading dose. The two groups were comparable also for the decrease evolution of parasitemia. Case-fatality rates were also similar: 95% of healing at the 72nd hour and a lethality rate between 5 and 6% in the two groups. But a significant increase of the body temperature was noted between the 51st and the 63rd hour in the group without loading dose. No significant cardiovascular toxicity was noticed in the two groups. The mean cost of the loading dose regimen was less than that of the second regimen.

CONCLUSION

The loading dose regimen of quinine is well tolerated and it seemed slightly more effective than the regimen without loading dose. In cases of contra-indications (patients who recently received quinine, mefloquine or halofantrine), regimens without loading dose, which remains effective, should be used.

Pharmacokinetics of quinine, chloroquine and amodiaquine. Clinical implications

Malaria is associated with a reduction in the systemic clearance and apparent volume of distribution of the cinchona alkaloids; this reduction is proportional to the disease severity. There is increased plasma protein binding, predominantly to alpha 1-acid glycoprotein, and elimination half-lives (in healthy adults quinine t1/2z = 11 hours, quinidine t1/2z = 8 hours) are prolonged by 50%. Systemic clearance is predominantly by hepatic biotransformation to more polar metabolites (quinine 80%, quinidine 65%) and the remaining drug is eliminated unchanged by the kidney. Quinine is well absorbed by mouth or following intramuscular injection even in severe cases of malaria (estimated bioavailability more than 85%). Quinine and chloroquine may cause potentially lethal hypotension if given by intravenous injection. Chloroquine is extensively distributed with an enormous total apparent volume of distribution (Vd) more than 100 L/kg, and a terminal elimination half-life of 1 to 2 months. As a consequence, distribution rather than elimination processes determine the blood concentration profile of chloroquine in patients with acute malaria. Parenteral chloroquine should be given either by continuous intravenous infusion, or by frequent intramuscular or subcutaneous injections of relatively small doses. Oral bioavailability exceeds 75%. Amodiaquine is a pro-drug for the active antimalarial metabolite desethylamodiaquine. Its pharmacokinetic properties are similar to these of chloroquine although the Vd is smaller (17 to 34 L/kg) and the terminal elimination half-life is 1 to 3 weeks.

Intrarectal Quinimax (an association of Cinchona alkaloids) for the treatment of Plasmodium falciparum malaria in children in Niger: efficacy and pharmacokinetics

In an attempt to avoid the complications associated with intramuscular quinine administration, we assessed the intrarectal route. Sixty-six children aged from 2 to 10 years with Plasmodium falciparum malaria were included in the study, which took place in Niamey, Niger. Fifty-five children were given 20 mg/kg of the diluted injectable form of Quinimax (a quinine, quinidine, cinchonine, cinchonidine association) intrarectally. A further 11 children with malaria were treated with 12.5 mg/kg of the same Quinimax solution by the intramuscular route. All the children were treated twice a day for 3 d. Blood samples were drawn from 20 children (15 treated intrarectally and 5 intramuscularly) for a kinetic study. Both modes of administration were well tolerated. Mean fever clearance times (+/- standard errors) were 48.6 +/- 2.7 h and 35.9 +/- 2.2 h in the intrarectal and intramuscular groups, respectively (P = 0.05). Mean parasite clearance times (+/- standard errors) and mean times to achieve 50% reduction in parasitaemia (+/- standard errors) were similar after intrarectal (46.5 +/- 5.7 h and 7.8 +/- 0.9 h respectively) and intramuscular administration (27.4 +/- 3.6 h and 8.7 +/- 1.7 h, respectively). Tmax. after intrarectal administration (2.7 +/- 0.4 h) did not differ significantly from the value after intramuscular administration (1.1 +/- 0.6 h), but Cmax. and the area under the concentration-time curve from 0 to 48 h were lower (4.9 +/- 0.6 mg/L and 230.0 +/- 9.6 mg/L.h, respectively) than after intramuscular administration (9.1 +/- 1.2 mg/L and 356.0 +/- 4.2 mg/L.h, respectively) (P < 0.001). Compared to the intramuscular route, intrarectal Quinimax bioavailability was 40%.(ABSTRACT TRUNCATED AT 250 WORDS)

Towards optimal regimens of parenteral quinine for young African children with cerebral malaria: unbound quinine concentrations following a simple loading dose regimen

Nine children with severe falciparum malaria were treated with an intravenous quinine regimen which did not require burettes or infusion pumps, to determine its practicability and to ensure that therapeutic drug concentrations were achieved and maintained throughout the dose interval. The regimen comprised quinine dihydrochloride (15 mg/kg; 12.5 mg/kg of the free base), which was added to a bag of intravenous fluid (after wastage of all but 100 mL), and given via standard giving sets over 2 h. Blood was drawn sequentially during the infusion, and for 12 h thereafter; plasma water was obtained by ultrafiltration of samples at the bedside, and quinine concentration was measured, in plasma and plasma water, by high performance liquid chromatography. Drug administration was practicable without burettes or infusion pumps; unbound drug concentrations exceeded the 99% inhibitory concentration for local parasites within 0.5 h, and remained within the therapeutic range for the entire dose interval. This loading dose regimen can now be recommended for young children in African hospitals; maintenance doses of 10 mg/kg should be given at 12 h intervals until oral antimalarial drugs are possible. These recommendations will need to be modified if susceptibility to quinine declines.

Comparison of intramuscular and intravenous quinine for the treatment of severe and complicated malaria in children

To compare the efficacy and side effects of intramuscular (i.m.) and intravenous (i.v.) quinine, children in Mozambique with severe and complicated malaria between 6 months and 7 years were randomized to treatment with i.m. or i.v. quinine, both in a dosage of quinine dihydrochloride 20 mg/kg followed by 10 mg/kg every 8 h. Of 57 children treated with i.m. quinine, 4 died, 3 had neurological sequelae and 2 had sterile intramuscular abscesses. Of 47 children treated with i.v. quinine, 6 died and 1 had neurological sequelae. The mean parasite clearance time was 58.6 h in the i.m. group and 59.3 h in the i.v. group. Mean temperature clearance times were 56.1 and 51.8 h, and mean coma clearance times 40.4 and 38.7 h, respectively. None of these differences was statistically significant. Mean trough and peak concentrations of quinine were almost identical in the 2 groups, ranging from 10.5 to 12.6 mg/L, which is in the therapeutic non-toxic range. It is concluded that i.m. quinine is as effective as quinine by i.v. infusion in children with severe and complicated malaria; that minor local side effects can probably be avoided by using diluted quinine for i.m. injection; and that the optimal dose regimen for children with severe and complicated malaria in Africa at present is probably quinine salt 20 mg/kg followed by 10 mg/kg every 12 h.

Diagnosis and treatment of malaria in Britain

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Towards optimal regimens of parenteral quinine for young African children with cerebral malaria: the importance of unbound quinine concentration

Young African children with severe malaria are given quinine using a regimen designed for Thai adults. We measured quinine in the blood, plasma and plasma water of young children in Kenya after rapid intravenous and intramuscular dosing, and calculated the therapeutic range of unbound quinine. The peak plasma quinine concentration after rapid intravenous dosing was 12.3 +/- 3.7 mg/L (mean +/- SD), 43% higher than in adults given the same regimen previously; this was due to a smaller apparent volume of distribution in the children. The therapeutic range of unbound quinine was calculated as 0.2-2.0 mg/L. Simulations of unbound quinine were made for the standard quinine regimen: unbound drug concentrations rose above the therapeutic range after each dose. The possible risks of quinine-induced visual impairment are discussed. Alternative, lower dose regimens for young African children with severe malaria are described.

Cerebral malaria in children

Cerebral malaria is a rapidly progressive encephalopathy with up to 50% mortality. A cardinal feature is the massing of red cells containing mature Plasmodium falciparum within the cerebral capillaries. Adhesion of these parasitised red cells to endothelium, an event which may initiate cerebral malaria, is being studied at the molecular level. However, the relevance of these studies to the pathophysiology and treatment of human cerebral malaria is uncertain. Although chloroquine is still widely used to treat falciparum malaria, resistance has spread to most of the endemic zone. Quinine is emerging as the only effective treatment for cerebral malaria, though resistance to this drug threatens to become a problem. Alternative drugs are urgently needed.

Geographical clustering of risk factors and lifestyle for coronary heart disease in the Scottish Heart Health Study

A large cross sectional study, the Scottish Heart Health Study, of 10,359 men and women from 22 districts of Scotland was undertaken to try to explain the geographical variation of coronary heart disease mortality. Analysis by district showed that of the classic risk factors only cigarette smoking was strongly associated with heart disease mortality among both men and women. Mean diastolic blood pressure was weakly associated with rates among men and high density lipoprotein cholesterol showed a strong negative association among women. Total cholesterol showed a weak negative association with heart disease mortality, but, because the serum concentrations of cholesterol were uniformly high in all districts, a strong association with mortality would not be expected. In both men and women many dietary factors showed moderate or strong associations with mortality from coronary heart disease in a district--of these a low consumption of vitamin C was most notable. Other factors associated with heart disease included alcohol consumption and serum triglycerides among men, and obesity, physical activity, and serum triglycerides among women. Many factors associated with heart disease showed strong intercorrelations. Clustering of risk factors (including smoking, alcohol, and diet among men, and smoking, diet, and obesity among women) was associated with much of the regional variation in heart disease mortality in Scotland.

The pharmacokinetic properties of intramuscular quinine in Gambian children with severe falciparum malaria

Plasma quinine concentrations were measured in 21 Gambian children with severe falciparum malaria after intramuscular administration of a 20 mg (salt) per kg loading dose of quinine dihydrochloride followed by 10 mg/kg at 12 h intervals. Quinine was well absorbed reaching mean peak concentrations of 15.6 (standard deviation [SD] 4.5) mg/litre in a median time of 3 h (range 1-6 h). A one compartment model was fitted to the plasma concentration-time profile. The mean estimated systemic clearance (Cl/F) was 0.89 (SD 0.81) ml/kg/min and the mean elimination half life was 18.8 (SD 8.0) h. Two patients, one of whom died, had low plasma quinine levels which remained below 10 mg/litre. Mean peak and trough plasma concentrations after subsequent intramuscular doses ranged between 11.1 and 15.1 mg/litre. In most cases this dose regimen provided a satisfactory profile of blood concentrations for the treatment of severe malaria in children.

The safety and kinetics of intramuscular quinine in Malawian children with moderately severe falciparum malaria

The safety and kinetics of intramuscular quinine (10 mg salt/kg every 8 h for 3 doses) were assessed in Malawian children suffering from uncomplicated falciparum malaria, who were unable to take oral antimalarial drugs. Treatment was completed with oral pyrimethamine-sulfadoxine. The mean (+/- SD) peak plasma quinine concentration after the first injection was 9.0 (+/- 2.3) micrograms/ml, at 1.1 (+/- 0.7) h. Mean plasma concentrations increased further after the second and third doses to a maximum of 11.5 (+/- 2.6) micrograms/ml at 16.1 (+/- 3.2) h. No hypotension, hypoglycaemia or electrocardiographic abnormalities developed during quinine treatment. These results provide further evidence for the safety of intramuscular quinine in children with moderately severe malaria. Plasma concentrations of alpha 1-acid glycoprotein (AGP) were higher, and the degree of protein binding of quinine was greater, in acute malaria than in convalescence. There was a significant correlation between AGP concentration and the fraction of plasma quinine bound to plasma protein. These findings suggest a role for AGP in the binding of quinine in plasma in vivo and are of interest since unbound quinine is responsible for both the efficacy and toxicity of the drug.

Treatment of malaria--1990

Malaria has become an increasingly common health problem in the 1970s and 1980s, both in areas where infection is endemic and in travellers returning to non-endemic areas. The severity of infection varies widely, depending on the plasmodial species involved, and there is an extensive chemotherapeutic armamentarium currently available to combat malarial infection. Drug chemistry, pharmacokinetics, mechanism of drug action and resistance, and toxicities are outlined for the cinchona alkaloids (quinine and quinidine), chloroquine, amodiaquine, pyrimethamine, the sulphonamides, pyrimethamine/sulfadoxine, mefloquine, pyrimethamine/sulfadoxine/mefloquine, the sesquiterpene lactones, primaquine, and other drugs. A knowledge of the distribution of drug resistance is vital for the provision of effective antimalarial therapy, and current information in this area is outlined. Chloroquine remains the mainstay of treatment for the erythrocytic stages of Plasmodium vivax, P. ovale, P. malariae, and chloroquine-sensitive P. falciparum malaria. The dormant hepatic stages of P. vivax and P. ovale also require further treatment with primaquine. Quinine, alone or in combination with other drugs, is the primary agent used to treat chloroquine-resistant falciparum malaria. Falciparum infection can rapidly become fatal, therefore its complications of multiple organ failure, heavy parasitaemias, cerebral malaria, and hypoglycaemia must be recognised and managed promptly. Because these protozoal parasitic infections are now encountered throughout the world and can become life-threatening, a wide variety of practitioners must become more familiar with their correct treatment.

Open comparison of intramuscular chloroquine and quinine in children with severe chloroquine-sensitive falciparum malaria

An open paired randomised comparison of intramuscular chloroquine (3.5 mg base/kg every 6 h) and intramuscular quinine (20 mg salt/kg followed by 10 mg/kg every 12 h) was carried out in 50 Gambian children with severe falciparum malaria. 8 children died, 6 from the quinine-treated and 2 from the chloroquine-treated group. Chloroquine reduced parasitaemia significantly more rapidly than did quinine, but other measures of the therapeutic response were similar in the two groups. Quinine injections were painful. These findings do not support the proposition that quinine is intrinsically superior to chloroquine in the treatment of severe drug-sensitive falciparum malaria.

Treatment of severe malaria

In the treatment of severe Plasmodium falciparum infection antimalarial drugs should, ideally, be given by controlled rate intravenous infusion until the patient is able to swallow tablets. In cases where infection has been acquired in a chloroquine resistant area, and where it has broken through chloroquine prophylaxis or where the geographical origin or species are uncertain, quinine is the treatment of choice. When access to parenteral quinine is likely to be delayed, parenteral quinidine is an effective alternative. A loading dose of quinine is recommended in order to achieve therapeutic plasma concentrations as quickly as possible. In the case of chloroquine sensitive P. falciparum infection, chloroquine, which can be given safely by slow intravenous infusion, may be more rapidly effective and has fewer toxic effects than quinine. There is limited experience with parenteral administration of pyrimethamine sulphonamide combinations such as Fansidar, and resistance to these drugs has developed in South East Asia and elsewhere. Mefloquine and halofantrine cannot be given parenterally. Qinghaosu derivatives are not readily available and have not been adequately tested outside China. Supportive treatment includes the prevention or early detection and treatment of complications, strict attention to fluid balance, provision of adequate nursing for unconscious patients and avoidance of harmful ancillary treatments. Anaemia is inevitable and out of proportion to detectable parasitaemia. Hypotension and shock ('algid malaria') are often attributable to secondary gram-negative septicaemia requiring appropriate antimicrobial therapy and haemodynamic resuscitation. Many patients with severe falciparum malaria are hypovolaemic on admission to hospital and require cautious fluid replacement. Failure to rehydrate these patients may lead to circulatory collapse, lactic acidosis, renal failure and severe hyponatraemia.(ABSTRACT TRUNCATED AT 250 WORDS)