quinine

Benjamin Clanner-Engelshofen is a freelance writer in the medical department. He studied biochemistry and pharmacy in Munich and Cambridge / Boston (USA) and noticed early on that he particularly enjoyed the interface between medicine and science. That is why he went on to study human medicine.

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The active ingredient quinine occurs naturally in the bark of the cinchona tree and is used as a medicinal substance and bitter substance. The quinine effect is used to lower fever, muscle cramps and malaria. The active ingredient is generally considered to be well tolerated. In rare cases, however, there are significant side effects. Here you can read everything you need to know about the question "What is quinine?", Its use and side effects.

This is how quinine works

Quinine works in different places in the body:

For example, it leads to muscle relaxation through various mechanisms. It ensures that the muscle fibers need a longer time after they have been contracted until they react again to nerve stimuli for contracting. On the other hand, the active ingredient inhibits the transmission of these nerve stimuli to the muscles, which also reduces their reactivity. Quinine also influences the distribution of calcium in muscles, which is also important for contraction.

The active ingredient quinine also has an antipyretic and analgesic effect. Extracts from the bark of the Chinese tree were used as medicinal products for this purpose very early on.

Furthermore, quinine was the only effective anti-malarial drug until around 1940. In this tropical-subtropical infectious disease, pathogenic protozoa attack the red blood cells (erythrocytes). To obtain protein building blocks (amino acids), they break down the oxygen-transporting hemoglobin in the erythrocytes. The iron-containing dye heme falls off as a breakdown product, which in its free form is toxic to the malaria pathogens. With the help of an enzyme, they connect the individual heme groups to form larger units and thus render them harmless. The active ingredient quinine inhibits this enzyme so that the heme remains free - the malaria pathogens are killed, while the high heme concentration is harmless to humans.

In the past, quinine was also used to stimulate labor. In the meantime, however, more effective and better tolerated means are available for this.

The abusive use of high doses of quinine as an abortion agent often leads to fatal kidney failure.

The uptake, breakdown and excretion of quinine

After oral ingestion, quinine is rapidly and completely absorbed into the blood in the upper part of the small intestine. The highest concentrations can be measured in the blood after about one to three hours. After about half a day, half of the amount of active ingredient absorbed is excreted via the kidneys, with a large part being metabolized by the liver beforehand.

When is quinine used?

Only one quinine preparation is approved as a finished medicinal product in Germany, which is used for the prevention and treatment of nocturnal calf cramps. The tablets contain the active ingredient in the form of quinine sulfate (the sulfuric acid salt of quinine, which is more soluble in water).

The active ingredient is also used in the treatment of complicated tropical malaria, in the form of an injection solution. This must be produced by the (hospital) pharmacy itself, there are no finished medicinal products available. Quinine is also recommended for pregnant malaria patients.

This is how quinine is used

For the treatment of nocturnal muscle cramps, a tablet with a quinine dose of 200 milligrams is taken after dinner for mild symptoms. For moderate to severe symptoms, two tablets are taken in the evening - one after dinner and one before bed. The duration of therapy should not last longer than two to three weeks, as the active ingredient can accumulate in the body. If symptoms persist, a doctor should be consulted.

Intravenous therapy for malaria infections is individual based on the severity of the infection and other criteria and is determined by the doctor.

What are the side effects of quinine?

The quinine side effects are collectively referred to as cinchonism and occur relatively frequently with long-term or high-dose administration. They include nausea, vomiting, diarrhea, headache, ringing in the ears (tinnitus), visual disturbances, skin rashes, cardiac arrhythmias, drop in blood pressure, kidney damage, blood disorders and hypersensitivity reactions. Most of the side effects are dose-dependent and disappear again after quinine therapy is discontinued.

What should be considered when taking quinine?

No data are available on the use of quinine in children and adolescents under 18 years of age, which is why its use is not recommended in these age groups. The dose may need to be reduced in elderly patients with decreased kidney function.

Drug interactions

The simultaneous use of magnesium or aluminum-containing agents for stomach acidification can impair the absorption of quinine. Such antacids are used, for example, in the treatment of heartburn and gastric ulcers.

We advise against the simultaneous use of other active ingredients that lead to a change in the heart rhythm (especially to a so-called QT time lengthening, i.e. an inhibition of the transmission of stimuli to the heart). These include drugs for arrhythmias (antiarrhythmics), drugs for psychoses (antipsychotics / neuroleptics), some antidepressants, antibiotics, allergy drugs (antihistamines) and strong pain relievers from the opioid group.

Quinine can increase the effects of digitalis preparations (heart medication), muscle relaxants (muscle relaxants) and anticoagulants.

In general, if you want to use other drugs in addition to quinine, you should speak to a doctor or pharmacist beforehand to be on the safe side.

Quinine & pregnancy

Since quinine can cross the placental barrier, it should not be used during pregnancy. Only use in malaria is recommended in the absence of alternatives.

The active ingredient passes into breast milk, which is why it is not recommended for breastfeeding.

How to get quinine medication

Quinine for nighttime calf cramps can still be obtained without a prescription from the pharmacy. In December 2013, however, the Federal Institute for Drugs and Medical Devices (BfArM) recommended that the active ingredient quinine be made subject to prescription requirements. One reason for this is the sometimes severe side effects. In addition, the active ingredient is misused in the drug scene to increase the effectiveness of the opioid loperamide (an over-the-counter treatment for diarrhea).

How long has quinine been known?

Quechua has long been used by the indigenous people of Peru, the Quechua, against shivering at lower temperatures. For this purpose, the ground bark of the cinchona tree was mixed with sweetened water and drunk, similar to the worldwide widespread tonic water, in which it is still used today as an aroma (bitter substance). The active ingredient quinine has been used to treat malaria since the 17th century and has long been the only remedy for this.

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