Quinine

1. Introduction

Quinine is an antimalarial medication derived from the bark of the cinchona tree. It is primarily used to treat malaria caused by Plasmodium falciparum. Quinine also has off-label uses for leg cramps and other conditions, but its use in non-malarial indications is limited due to safety concerns. It works by interfering with the parasite’s ability to digest haemoglobin, leading to its death.

2. Indications

  • Malaria: Treatment of uncomplicated and severe malaria caused by Plasmodium falciparum (when other treatments are not suitable or available).
  • Leg cramps (off-label): Used occasionally, though this use is discouraged due to safety concerns.

3. Dosage

Adults:

  • Uncomplicated malaria: 600 mg orally every 8 hours for 7 days (in combination with other antimalarials like doxycycline or clindamycin).
  • Severe malaria: 20 mg/kg loading dose IV over 4 hours, followed by 10 mg/kg every 8 hours until oral therapy is feasible. Transition to oral therapy with the same dosing schedule for a total treatment duration of 7 days.

Children:

  • Uncomplicated malaria: 10 mg/kg orally every 8 hours for 7 days (maximum 600 mg/dose).
  • Severe malaria: IV dosing is weight-based (20 mg/kg loading dose followed by 10 mg/kg every 8 hours).

Elderly:

  • Use cautiously due to increased risk of side effects like cardiac and auditory toxicity.

4. Administration

  • Oral: Take with food or after meals to minimise gastrointestinal side effects.
  • Intravenous: Administer by slow infusion (never as a rapid bolus) to reduce the risk of cardiac toxicity.
  • Ensure adequate hydration during treatment to reduce the risk of kidney complications.

5. Forms Available

  • Tablets: 200 mg, 300 mg, 600 mg
  • Intravenous solution: 300 mg/mL

6. Side Effects

6.1 Common Side Effects:

  • Nausea and vomiting
  • Diarrhoea
  • Abdominal pain
  • Tinnitus (ringing in the ears)
  • Headache

6.2 Less Common Side Effects:

  • Blurred vision
  • Muscle weakness
  • Dizziness

6.3 Rare but Serious Side Effects:

  • Cinchonism (a cluster of symptoms including tinnitus, blurred vision, headache, and hearing loss)
  • Cardiac arrhythmias, including QT prolongation
  • Severe hypersensitivity reactions (e.g., Stevens-Johnson syndrome)
  • Haemolytic anaemia (especially in individuals with G6PD deficiency)
  • Thrombocytopenia

7. Warnings

  • Cardiac Toxicity: Quinine can prolong the QT interval, leading to arrhythmias. Use cautiously in patients with pre-existing cardiac conditions.
  • Cinchonism: Overdose or prolonged use may lead to symptoms such as tinnitus, hearing loss, and visual disturbances.
  • Hypoglycaemia: Quinine stimulates insulin release, which may lead to dangerously low blood sugar levels, especially in pregnant women or patients receiving IV therapy.
  • Haemolysis: Risk of haemolytic anaemia in patients with G6PD deficiency.

8. Precautions

  • Avoid use in patients with a history of hypersensitivity to quinine or related compounds.
  • Use cautiously in patients with hepatic or renal impairment.
  • Avoid combining with other drugs that prolong the QT interval or lower blood glucose levels.

9. Interactions

  • Antimalarials (e.g., mefloquine): Increased risk of cardiac toxicity or seizures.
  • CYP3A4 inhibitors (e.g., ketoconazole): Increased quinine levels, leading to toxicity.
  • Anticoagulants (e.g., warfarin): Increased anticoagulant effects due to displacement from protein binding sites.
  • Drugs that prolong the QT interval (e.g., amiodarone): Increased risk of arrhythmias.

10. Monitoring Parameters

  • ECG monitoring to detect QT prolongation, especially in IV therapy.
  • Blood glucose levels, particularly in pregnant women or patients at risk of hypoglycaemia.
  • Signs of cinchonism (e.g., tinnitus, visual disturbances).
  • Haematological parameters, particularly in patients with G6PD deficiency.

11. Use in Children

  • Quinine is safe for use in children at weight-appropriate doses for malaria treatment. Close monitoring for side effects, including hypoglycaemia, is recommended.

12. Use in Pregnancy

  • Quinine is considered safe for malaria treatment in pregnancy but should be used cautiously due to the risk of hypoglycaemia. Avoid high doses to minimise toxicity to both mother and foetus.

13. Use in Elderly

  • Use cautiously in elderly patients due to an increased risk of cardiac toxicity, cinchonism, and drug interactions. Start at the lowest effective dose.

14. Use in Kidney Disease

  • Dose adjustments may be required in severe renal impairment due to reduced clearance of quinine.

15. Use in Liver Disease

  • Use cautiously in patients with hepatic impairment, as quinine is metabolised in the liver.

16. Patient Counselling Points

  • Take quinine as prescribed and complete the full course, even if symptoms improve.
  • Report symptoms such as tinnitus, dizziness, or visual disturbances to your doctor immediately.
  • Avoid consuming tonic water during treatment, as it contains small amounts of quinine and may increase the risk of toxicity.
  • Avoid combining quinine with other medications that affect the heart or blood sugar levels unless advised by your doctor.
  • Stay hydrated and follow your doctor’s recommendations during treatment.

17. Table of Brand Names, Manufacturer, and Prices in USD

Brand NameManufacturerStrength/Dosage FormPrice (USD)
QualaquinAR Scientific324 mg Capsule$50 (30 capsules)
Quinine SulfateGeneric300 mg Tablet$15 (30 tablets)
QuiniteVarious600 mg Tablet$20 (10 tablets)

18. 15 FAQs (Frequently Asked Questions)

1. What is Quinine used for?
Quinine is used to treat malaria and, in some cases, off-label for leg cramps (though not recommended).

2. How does Quinine work?
It interferes with the malaria parasite’s ability to digest haemoglobin, leading to its death.

3. Can Quinine cause tinnitus?
Yes, tinnitus is a common symptom of cinchonism, which may occur with quinine use.

4. Is Quinine safe for children?
Yes, quinine can be used in children at weight-appropriate doses for malaria treatment.

5. Can Quinine be used during pregnancy?
Yes, it is safe for treating malaria in pregnancy, but it should be used cautiously due to the risk of hypoglycaemia.

6. Can Quinine cause hypoglycaemia?
Yes, quinine can stimulate insulin release, leading to low blood sugar levels.

7. What are the signs of Quinine overdose?
Overdose symptoms include severe tinnitus, vision loss, confusion, seizures, and arrhythmias.

8. Can Quinine interact with other medications?
Yes, it interacts with drugs like mefloquine, CYP3A4 inhibitors, anticoagulants, and QT-prolonging medications.

9. How should Quinine be taken?
Take it with food to reduce gastrointestinal side effects and complete the full course of treatment.

10. Is Quinine available over the counter?
No, quinine is available by prescription only due to safety concerns.

11. Can Quinine cause cardiac problems?
Yes, it can prolong the QT interval and increase the risk of arrhythmias.

12. Can Quinine cause haemolysis?
Yes, particularly in individuals with G6PD deficiency.

13. How long does it take for Quinine to work?
Symptoms of malaria usually improve within 48–72 hours of starting treatment.

14. Can I drink tonic water while taking Quinine?
No, tonic water contains small amounts of quinine and may increase the risk of side effects.

15. What should I do if I miss a dose?
Take the missed dose as soon as you remember, but skip it if it is close to the next scheduled dose.