Clinical pharmacokinetics of quinine and its relationship with treatment outcomes in children, pregnant women, and elderly patients, with uncomplicated and complicated malaria: a systematic review

Background

Standard dosage regimens of quinine formulated for adult patients with uncomplicated and complicated malaria have been applied for clinical uses in children, pregnant women, and elderly. Since these populations have anatomical and physiological differences from adults, dosage regimens formulated for adults may not be appropriate. The study aimed to (i) review existing information on the pharmacokinetics of quinine in children, pregnant women, and elderly populations, (ii) identify factors that influence quinine pharmacokinetics, and (iii) analyse the relationship between the pharmacokinetics and treatment outcomes (therapeutic and safety) of various dosage regimens of quinine.

Methods

Web of Sciences, Cochrane Library, Scopus, and PubMed were the databases applied in this systematic search for relevant research articles published up to October 2020 using the predefined search terms. The retrieved articles were initially screened by titles and abstracts to exclude any irrelevant articles and were further evaluated based on full-texts, applying the predefined eligibility criteria. Excel spreadsheet (Microsoft, WA, USA) was used for data collection and management. Qualitative data are presented as numbers and percentages, and where appropriate, mean + SD or median (range) or range values.

Results

Twenty-eight articles fulfilled the eligibility criteria, 19 in children, 7 in pregnant women, and 2 in elderly (14 and 7 articles in complicated and uncomplicated malaria, respectively). Severity of infection, routes of administration, and nutritional status were shown to be the key factors impacting quinine pharmacokinetics in these vulnerable groups.

Conclusions

The recommended dosages for both uncomplicated and complicated malaria are, in general, adequate for elderly and children with uncomplicated malaria. Dose adjustment may be required in pregnant women with both uncomplicated and complicated malaria, and in children with complicated malaria. Pharmacokinetics studies relevant to clinical efficacy in these vulnerable groups of patients with large sample size and reassessment of MIC (minimum inhibitory concentration) should be considered.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04065-1.

Physiologically based pharmacokinetic modeling for dose optimization of quinine-phenobarbital coadministration in patients with cerebral malaria

Patients with cerebral malaria with polymorphic Cytochrome P450 2C19 (CYP2C19) genotypes who receive concurrent treatment with quinine are at risk of inadequate or toxic therapeutic drug concentrations due to metabolic drug interactions. The study aimed to predict the potential dose regimens of quinine when coadministered with phenobarbital in adult patients with cerebral malaria and complications (e.g., lactic acidosis and acute renal failure) and concurrent with seizures and acute renal failure who carry wild‐type and polymorphic CYP2C19. The whole‐body physiologically based pharmacokinetic (PBPK) models for quinine, phenobarbital, and quinine–phenobarbital coadministration were constructed based on the previously published information using Simbiology®. Four published articles were used for model validation. A total of 100 virtual patients were simulated based on the 14‐day and 3‐day courses of treatment. using the drug–drug interaction approach. The predicted results were within 15% of the observed values. Standard phenobarbital dose, when administered with quinine, is suitable for all groups with single or continuous seizures regardless of CYP2C19 genotype, renal failure, and lactic acidosis. Dose adjustment based on area under the curve ratio provided inappropriate quinine concentrations. The recommended dose of quinine when coadministered with phenobarbital based on the PBPK model for all groups is a loading dose of 2000 mg intravenous (i.v.) infusion rate 250 mg/h followed by 1200 mg i.v. rate 150 mg/h. The developed PBPK models are credible for further simulations. Because the predicted quinine doses in all groups were similar regardless of the CYP2C19 genotype, genotyping may not be required.

Physiologically-Based Pharmacokinetic Modeling for Optimal Dosage Prediction of Quinine Coadministered With Ritonavir-Boosted Lopinavir

The coformulated lopinavir/ritonavir significantly reduces quinine concentration in healthy volunteers due to potential drug-drug interactions (DDIs). However, DDI information in malaria and HIV coinfected patients are lacking. The objective of the study was to apply physiologically-based pharmacokinetic (PBPK) modeling to predict optimal dosage regimens of quinine when coadministered with lopinavir/ritonavir in malaria and HIV coinfected patients with different conditions. The developed model was validated against literature. Model verification was evaluated using the accepted method. The verified PBPK models successfully predicted unbound quinine disposition when coadministered with lopinavir/ritonavir in coinfected patients with different conditions. Suitable dose adjustments to counteract with the DDIs have identified in patients with various situations (i.e., a 7-day course at 1,800 mg t.i.d. in patients with malaria with HIV infection, 648 mg b.i.d. in chronic renal failure, 648 mg t.i.d. in hepatic insufficiency except for severe hepatic insufficiency (324 mg b.i.d.), and 648 mg t.i.d. in CYP3A4 polymorphism).

Pharmacokinetic Parameters of Quinine in Healthy Subjects and in Patients with Uncomplicated Malaria in Nigeria: Analysis of Data using a Population Approach

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Varied disposition imparts on the tolerance and safety of quinine, and thus constitutes a major limiting consideration for its dosing in uncomplicated malaria. Utilizing a population approach, the effect of body weight and infection status on disposition parameters of quinine were evaluated in Nigerian subjects.

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A reversal of infection-induced changes in volume of distribution and clearance after 48 h of chronic quinine administration was noted.

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It is hypothesized that a downward review of quinine regimen post-48 h of chronic administration, in the event of complete parasitaemia clearance, might be a useful approach in enhancing tolerance and safety.

Background

The varied disposition of the antimalarial quinine partly explains its poor tolerance and toxicity in humans.

Objective

Using a population approach, the disposition of quinine in healthy subjects and patients with acute uncomplicated symptomatic malaria from Nigeria was re-examined with a view to providing population-specific attributes.

Methods

Concentration versus time profiles of quinine over 48 hours in healthy individuals, and over 7 days in malaria-infected patients, were stratified to reflect: concentration versus time data during the first 48 hours of quinine administration for healthy subjects and infected patients, concentration versus time data after 48 hours in infected patients, and all concentration versus time data available for healthy subjects and infected patients. Pharmacokinetic parameters were then estimated with a stochastic approximation expectation maximization algorithm.

Results

All datasets were fitted by a 1-compartment model with covariate contributions from body weight and infection status. The absorption rate constant, and volume of distribution and clearance were 1.72 h^–1, 86.8 to 157.4 L, and 6.6 to 9.6 L/h, respectively. Infected patients experienced a 38% decrease in volume of distribution and a 31% decrease in clearance in the first 48 hours relative to healthy individuals. The contraction in volume of distribution and clearance diminished significantly after 48 hours of chronic quinine dosing in infected patients.

Conclusions

The study findings suggest that clinical interventions aimed at enhancing the safety and tolerance of quinine might be achieved by a rational decrease in dose size and/or dosing interval, post-48 hours of chronic quinine administration, in malaria-infected patients.

Quinine unbound concentration is the best marker for therapeutic drug monitoring

Quinine monitoring should be based on unbound concentration due to variable unbound fraction in malaria patients.