Codeine is an active substance which, like morphine, belongs to the group of opiates. Nowadays it is mainly taken as a substance to relieve irritable cough and as a painkiller. Three opiates – codeine, morphine and thebaine – occur naturally in opium, the dried latex of the opium poppy, and can be extracted from it.
However, codeine is mainly produced synthetically. It can also be produced from other opiates. In Switzerland, codeine is considered a narcotic, but only high doses are available on prescription.
In low doses, it is not subject to narcotics regulations and can be purchased without a prescription. In Germany, on the other hand, codeine can only be purchased on presentation of a prescription. It should not be used in children under 2 years of age.
Effect and use
Codeine can be swallowed as tablets, capsules, drops, effervescent tablets or juice, taken as suppositories or given as a liquid directly into the vein. For children aged 2-12 years, drops with a low active ingredient content are common. The maximum amount of codeine that an adult can take should not exceed 200 mg or, in exceptional cases, 300 mg. For children under 6 years of age the maximum daily dose is 30 mg, for children under 12 years of age 60 mg. Much higher doses can be life-threatening due to the side effects (see below).
All opioids basically act on certain nerve cells in the brain and cause an inhibition of the transmission of stimuli. Therefore, they generally have a calming and inhibiting effect on the sensation of pain and the urge to cough. After taking codeine, about 10% of the amount taken is converted to morphine.
This proportion of morphine mainly causes the analgesic effect. It is important to note that codeine is converted to morphine to different degrees in different people, which can result in different levels of effectiveness. The reason for this are different, genetically predisposed variants of the substance that converts codeine to morphine.
Approximately 10% of the white population convert codeine to morphine to a lesser extent, which is why it has a lesser effect, and up to 5% have a stronger effect. In the latter case, codeine should only be used under strict control and after being informed about the possible side effects, as an overdose can quickly occur. The analgesic effect of codeine is on average about 1/10 as strong as the analgesic effect of pure morphine of the same dose.
Codeine therefore belongs to the so-called “weakly effective opioids“. Compared to other substances in this group, however, it triggers stronger side effects with less effect, which is why it is not used as the first choice in the treatment of pain. Better alternatives from the group of opioids for stronger pain are tramadol or buprenorphine.
Codeine is usually used as an additive to weaker painkillers like diclofenac, acetylsalicylic acid (aspirin) or paracetamol for mild pain when a so-called “non-steroidal” painkiller – i.e. a weaker painkiller that does not belong to the group of opiates – is no longer sufficient. Codeine also has an inhibitory effect on the cough centre (“antitussive”) of the brain. Due to this effect, it is used especially for nocturnal irritable coughing, in which no mucus is coughed up.
In this case it is the first choice, as there are no better alternatives for cough control. In principle, however, codeine should not be taken to inhibit a cough with expectoration of mucus. This can aggravate the causative disease by suppressing the natural defence process in the lungs.
In the past, codeine was often used to treat diarrhoea because, like all opioids, it slows down movements of the stomach and intestines, allowing food to remain in the bowel tube for longer. However, it has now been replaced by loperamide. The latter acts at the same point of attack of the gastrointestinal system as codeine, but cannot reach the brain and thus no longer trigger various side effects. In the past, it was also used to relieve the symptoms of heroin withdrawal, for example. However, this is no longer done today.
