Quinine sulphate: salt form of quinine for cramps and malaria
Quinine sulphate (Chininsulfat) is the classic salt form of quinine, an alkaloid from the bark of the South American cinchona tree. The best-known German preparation is Limptar N, used for decades for nocturnal calf cramps. Internationally, quinine sulphate is also a fixed component of malaria therapy, especially in severe Plasmodium falciparum malaria when artemisinin derivatives are not available.
Quinine is closely related to its D-stereoisomer quinidine, used mainly as antiarrhythmic. Both share the typical side-effect pattern of cinchona alkaloids, called cinchonism, with tinnitus, headache and gastrointestinal complaints.
Mechanism of action
Quinine acts at several targets:
- Antimalarial: inhibition of haemozoin formation in Plasmodium erythrocyte stages; accumulation of toxic haem breakdown products kills the parasite
- For calf cramps: prolongation of the refractory period of striated muscle and reduction of neuromuscular excitability, presumably via sodium channels
- Antiarrhythmic: like quinidine, inhibition of cardiac sodium channels; clinically relevant for risk assessment in cramp therapy
Quinine is mainly metabolised hepatically with a half-life of 8 to 14 hours. With severe malaria or renal impairment the action can be prolonged.
Indications
- Severe and complicated falciparum malaria: intravenous therapy, especially with resistance or unavailability of artemisinin derivatives; classic WHO reserve therapy
- Calf cramps (nocturnal leg cramps): main indication in Germany, especially in older patients
- Babesiosis: off-label in combination with clindamycin
- Off-label: some cramp forms, restless legs-like complaints
Important: quinine sulphate is not recommended for prophylaxis of nocturnal cramps without clinical indication. Due to the side-effect profile and risk of severe complications (haemolysis, thrombocytopenia), the indication must be strictly reviewed.
Dosing and administration
Calf cramps (Limptar N, quinine sulphate): 200 mg in the evening, half an hour before going to bed. If needed up to 400 mg per day, in exceptional cases.
Falciparum malaria: adults 10 mg per kg body weight (salt) intravenously as initial dose over 4 hours, then 10 mg per kg every 8 hours over 7 days, combined with doxycycline or clindamycin.
Take orally with water, preferably on an empty stomach or with a meal depending on tolerability.
Treatment duration for cramps: not more than 2 to 4 weeks without reassessment, as the benefit-risk ratio worsens with longer use. Regular omission trials.
Side effects
Common: cinchonism with tinnitus, headache, dizziness, hearing loss, visual disturbance, nausea, abdominal pain, diarrhoea.
Uncommon: allergic reactions, hypoglycaemia (especially in pregnant and critically ill), hypotension, cardiac conduction disorders, pruritus, rash.
Rare and very rare: thrombocytopenia with bleeding tendency (quinine-induced thrombocytopenia), haemolytic anaemia (especially with G6PD deficiency), thrombotic thrombocytopenic purpura (TTP), haemolytic uraemic syndrome (HUS), Stevens Johnson syndrome, anaphylaxis.
Important risks:
- Quinine-induced thrombocytopenia: may be asymptomatic at first contact, severe bleeding on re-exposure; if suspected, stop therapy immediately
- Contraindicated in patients with G6PD deficiency
- QT prolongation with risk of torsade de pointes
- In pregnancy and severe renal impairment: caution and close monitoring
Interactions
- Other QT-prolonging substances (class 1a or 3 antiarrhythmics, methadone, some antipsychotics, macrolides, fluoroquinolones): additive QT prolongation, torsade de pointes risk
- Coumarins (warfarin, phenprocoumon): potentiated effect, monitor INR
- Digoxin: level increase
- Ciclosporin: reduced immunosuppressive efficacy
- Aluminium-containing antacids: reduced absorption
- Cimetidine: raised quinine levels
- Quinidine: additive effect, avoid combination
Special considerations
Pregnancy: acceptable in severe malaria therapy as the benefit outweighs the risk. Risk of hypoglycaemia and occasional placental passage. In calf cramps contraindicated.
Breastfeeding: passage into milk, individual judgement; contraindicated in infants with G6PD deficiency.
Contraindications: known hypersensitivity, G6PD deficiency, pre-existing tinnitus history, optic neuritis, thrombocytopenia after prior quinine exposure, myasthenia gravis, long QT syndrome.
Older patients: increased sensitivity, fall risk through dizziness.
Tonic water caution: tonic water contains small amounts of quinine (typically 80 mg per litre). Theoretically a very high intake can cause symptoms in sensitive patients; in practice the concentration is mostly below clinically relevant thresholds.
Patient communication: realistic expectations matter. Efficacy against calf cramps is only moderate compared with magnesium or stretching; risk of thrombocytopenia and other complications exists. Discuss non-drug measures before therapy.
Related substances
- Quinidine, D-stereoisomer used as antiarrhythmic
- Protamine in acute anticoagulation reversal
- Methotrexate as example of further reserve therapies
- Etomidate as alternative anaesthetic
Frequently asked questions
Does quinine sulphate reliably help against calf cramps?
Studies show a moderate effect on frequency and severity of nocturnal calf cramps. Due to rare but serious side effects such as thrombocytopenia, the indication has narrowed. Usually non-drug measures such as stretching and adequate fluid intake are tried first before considering quinine sulphate.
What is cinchonism?
Cinchonism describes typical poisoning symptoms from cinchona alkaloids: tinnitus, hearing loss, visual disturbance, dizziness, headache and gastrointestinal complaints. Usually mild at therapeutic doses, more severe at higher doses. Its appearance signals adjustment or reassessment of therapy.
Can tonic water be dangerous?
Tonic water contains about 80 mg of quinine per litre, harmless at normal intake. In sensitive individuals or with very high intake, symptoms can occur. In pregnancy, regular tonic water consumption should be avoided.
What alternatives exist for calf cramps?
Stretching (before bed), adequate fluid intake, magnesium supplementation (if a deficiency is present), vitamin B complex, adjusting exercise intensity. For specific conditions such as restless legs syndrome or neuromuscular cramps, other therapies are considered.
Sources
- BfArM Federal Institute for Drugs and Medical Devices
- EMA European Medicines Agency
- AWMF guidelines calf cramps and malaria
- Gelbe Liste quinine sulphate monograph
Legal notice and disclaimer
The information on this page is provided for general information purposes only and does not constitute medical advice, diagnosis or treatment recommendation. It does not replace the advice of a licensed physician or pharmacist. Medicines should only be used after a doctor's prescription or pharmacy supply. All information is based on summaries of product characteristics and accepted scientific sources at the time of writing; the current SmPC of the manufacturer is always decisive. Sanoliste accepts no liability for completeness, timeliness or accuracy. In a medical emergency, dial the emergency number 112.