Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2022 Publisher: Strides Pharma UK Ltd, Unit 4 Metro Centre, Tolpits Lane, Watford, Hertfordshire, WD18 9SS
Pharmacotherapeutic group: Antimalarials, Methanolquinolines
ATC Code: P01BC01
Quinine is a cinchona alkaloid and a 4-methanolquinoline antimalarial agent which is a rapidly acting blood schizontocide with activity against Plasmodium falciparum, P. vivax, P. ovale and P. malariae. It is active against the gametocytes of P. malariae and P. vivax but not against mature gametocytes of P. falciparum. Since it has no activity against exoerythrocyctic forms, quinine does not produce a radical cure in vivax or ovale malarias.
Quinine has effects on the motor end-plate of skeletal muscle and prolongs the refractory period. Like quinidine, quinine is a sodium channel blocker and, therefore, has local anaesthetic, and both anti-and proarrhythmic activity.
The precise mechanism of action of quinine is unclear but it may interfere with lysosome function or nucleic acid synthesis in the malaria parasite.
Quinine increases the refractory period of muscle so that the tetanic stimulation is diminished. It also affects a number of other body systems including the central nervous system, the cardiovascular system, the gastrointestinal tract and the pancreas. In addition, quinine exhibits local anaesthetic action and a local irritant action. As an antimalarial drug it acts primarily as a schizontocide. It is more toxic and less effective than chloroquine, but is especially useful for treatment of chloroquine-resistant strains of malarial infection.
The pharmacokinetics of quinine are altered significantly by malaria infection, the major effects being reductions in both its apparent volume of distribution and its clearance.
Quinine is rapidly and almost completely absorbed from the gastrointestinal tract and peak concentrations in the circulation are attained about 1-3 hours after oral administration of the sulfate.
Plasma protein binding is about 70% in healthy subjects and rises to 90% or more in patients with malaria. Quinine is widely distributed throughout the body. Concentrations attained in the CSF of patients with cerebral malaria have been reported to be about 2-7% of those in the plasma.
Quinine is extensively metabolised in the liver and rapidly excreted mainly in the urine. Estimates of the proportion of unchanged quinine excreted in the urine vary from less than 5% to 20%. The pharmacokinetics of quinine are altered significantly by malaria infection, with reductions in both the apparent volume of distribution and clearance.
Excretion is increased in acid urine. The elimination half-life is about 11 hours in healthy subjects but may be prolonged in patients with malaria. Small amounts of quinine also appear in the bile and saliva.
Quinine crosses the placenta and is excreted in the breast milk.
No data of relevance to the prescriber, which is additional to that included in other sections of the SPC.
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