Quinine

Products

Quinine is approved in many countries in the form of dragées for malaria therapy (quinine sulfate 250 Hänseler). In Germany, film-coated tablets of 200 mg quinine sulfate are commercially available for the treatment of calf cramps (Limptar N).

Structure and properties

Quinine (C20H24N2O2, Mr = 324.4 g/mol) usually exists as quinine sulfate, a white crystalline powder or fine colorless needles that are sparingly soluble in water. Quinine has a very bitter taste. It is a quinoline derivative found in the bark of the quinine tree.

Effects

Quinine (ATC P01BC01, ATC M09AA02) has antiparasitic, muscle relaxant, and antipyretic properties. At the muscle, quinine prolongs the refractory period, reduces excitability at the motor endplate, and affects the distribution of calcium in the muscle fiber. Thus, it increases the threshold for a response of the muscle to stimuli. Comment: Quinine sulfate has been used for decades for the treatment of idiopathic calf cramps. However, because of its adverse effects, potential for interaction, and possible toxicity in overdose, its use for this indication has been critically discussed. For example, in the U.S., approval for the treatment of calf cramps was withdrawn in 1995 after the FDA concluded that the potential benefits did not outweigh the risks. The U.S. Food and Drug Administration and some publications advise against its use for this purpose.

Indications for Use

Malaria:

  • Quinine is approved in many countries for the treatment of acute attacks of chloroquine-resistant malaria infections caused by.

Nighttime calf cramps:

  • In Germany, quinine is approved for the prevention and treatment of nocturnal calf cramps in adults. In many countries, this is no longer a registered indication (off-label).

As a bitter remedy:

  • Quinine is also used in small quantities as a bittering agent, for example, for the preparation of Indian Tonic Water (eg Schweppes).

Dosage

According to the professional information. For the treatment of calf cramps, one tablet of 200 mg is taken after dinner. The maximum daily dose is two tablets per day.

Contraindications

  • Hypersensitivity
  • Pregnancy and lactation
  • Glucose-6-phosphate dehydrogenase deficiency
  • Myasthenia gravis
  • Tinnitus
  • Pre-damage of the optic nerve
  • Untreated hypokalemia
  • Known bradycardia and other clinically relevant cardiac arrhythmias.
  • Severe decompensated heart failure
  • Congenital long QT syndrome or corresponding family history.
  • Known acquired QT interval prolongation.
  • Children and adolescents under 18 years of age

For complete precautions, see the drug label.

Interactions

Quinine is a substrate of CYP3A4 and other CYP450 isozymes are involved in metabolism. Corresponding interactions with CYP inhibitors and inducers may occur. Quinine may prolong the QT interval and should not be combined with other drugs that also prolong it. Several other drug-drug interactions have been described, for example, with muscle relaxants, antiarrhythmics, urinary alkalinizing agents, pyrimethamine, vitamin K antagonists, and antacids (selection).

Adverse effects

Possible adverse effects include (selection):

  • Nausea, vomiting, and diarrhea
  • Hypersensitivity reactions
  • Blood count changes, thrombocytopenia
  • Hemolytic uremic syndrome
  • Liver dysfunction
  • Visual disturbances
  • Tinnitus, hearing disorders, dizziness
  • Cardiac arrhythmias, palpable heartbeats.