How codeine works
Codeine dampens the cough reflex by inhibiting the cough center in the brain stem. According to current doctrine, this codeine effect is mainly due to morphine – a metabolic intermediate (metabolite) to which codeine is converted in small amounts in the liver. However, there is also evidence that codeine-6-glucuronide is responsible for the effect. This is another metabolite formed in the liver from codeine.
The analgesic effect is mainly due to the metabolic intermediate morphine. Codeine itself can also dock to the docking sites of opioids (opioid receptors), but with less binding ability.
Like all opioids, codeine also has a constipating as well as sedative effect.
Cough
Coughing is a healthy defensive response of the body. It helps to remove foreign bodies from the respiratory tract – bacteria, viruses or, for example, smoke particles are coughed up together with some mucus (“productive cough”). The impulse for this is provided by the cough center in the brain stem, to which the irritation of the mucous membrane by the foreign body is reported via nerve pathways.
In the case of irritation or inflammation of the mucous membrane, however, the coughing stimulus can also occur when there is no secretion at all in the airways. This is known as a “dry irritable cough”. This has no physiological benefit.
In the form of drops, cough syrup or tablets, codeine is taken by mouth (orally). The active ingredient is rapidly absorbed from the small intestine and absorbed into the blood. Therefore, after ingestion on an empty stomach, maximum levels of active ingredient are reached after about one hour.
In the liver, codeine is broken down into intermediates (including morphine) and then excreted through the kidneys in the urine.
When is codeine used?
Codeine is mainly used for the treatment of dry irritable cough. In combination with paracetamol, however, the active ingredient can also be used as an analgesic.
How codeine is used
For irritable cough, the codeine dosage is adjusted to the patient’s cough frequency and strength. Adults and adolescents over twelve years of age without other severe respiratory conditions may take a maximum of 200 milligrams of the active ingredient per day.
The total daily dose is usually divided into four individual doses. The last dose should preferably be taken just before bedtime to prevent cough irritation from disturbing sleep.
Due to serious side effects, some of which have been fatal, the European Medicines Agency (EMA) recommends that codeine no longer be used in children under the age of twelve.
What are the side effects of codeine?
Mild headache and drowsiness are common.
Occasionally, sleep disturbances, shortness of breath or dry mouth occur.
Rarely, severe allergic reactions (such as Stevens-Johnson syndrome) develop.
Overdose
Symptoms of opiate poisoning may develop if doses are too high or in people who convert the drug to morphine particularly quickly due to genetic conditions. These include euphoria or increased drowsiness, a decrease in respiratory drive (respiratory depression), a drop in blood pressure, disturbances in voluntary movements (ataxia) and muscle cramps.
In this context, the codeine/alcohol mixture may exacerbate the symptoms of an overdose.
If you suffer from any of the above side effects after codeine use, or if you have not experienced any symptoms until then, please consult your doctor.
When should codeine not be taken?
Contraindications
Codeine should not be used in:
- hypersensitivity to the active substance or to any of the other ingredients of the drug
- insufficient breathing capacity (respiratory insufficiency) or impaired breathing control (respiratory depression)
- @ pneumonia
- acute asthma attack
- children under twelve years of age
- approaching birth
- threatened premature birth
- Patients who are known to be “ultrafast CYP2D6 metabolizers,” i.e., who convert codeine to morphine very rapidly
Interactions
Trafficability and operation of machines
Codeine has an anticonvulsant effect and has side effects that impair the ability to react. Therefore, active participation in road traffic and the operation of machines should be avoided for the duration of use.
In the case of long-term use, for example as part of an overall therapeutic concept for chronic pain, individual tolerance should be waited for before getting behind the wheel of a motor vehicle or operating machinery again.
Age restriction
Codeine is contraindicated in children under twelve years of age.
Pregnancy and lactation
Women should not take codeine during pregnancy. The active ingredient may cross the placenta and enter the body of the unborn child. There is evidence that codeine can cause malformations in the embryo during the first three months. In addition, if the drug is used shortly before birth, it can cause respiratory depression in the child.
Only in justified cases may codeine be used as a short-term cough suppressant during pregnancy in cases of persistent irritable cough and failure of physical measures.
How to obtain medicines containing codeine
Preparations containing codeine are subject to prescription in Germany without restriction.
Codeine is also available on prescription in Austria. However, only one finished preparation is available here, which is why the prescription is often based on a magistral preparation. This means that the pharmacist prepares a codeine-containing drug individually for patients on the basis of a doctor’s prescription.
In Switzerland, codeine falls into dispensing category B and is included here with some other active ingredients in the so-called B+ list. This means that codeine can also be obtained without a doctor’s prescription – after a detailed consultation with a pharmacist.
