Codeine constipation

Codeine constipation

Codeine is a drug which is well known to cause constipation. Codeine is also known as 3-methoxymorphine. It does not have euphoric effects and so it is freely available over the counter. But it only has 20% of the analgesic potency of morphine. (With in the body codeine is converted morphine by an enzymatic reaction) So it is used to treat mild types of pain such as headache, backache and toothache etc.
Codeine constipation is due to its effect on the gastrointestinal tract. It increases the tone and reduces the motility in many parts of the gastro intestinal tract. Since this reduces the gastric emptying and reduces the rate of movement of food in the gastro intestinal tract this produces small amount of hard stools due excessive water absorption. Sometimes codeine constipation can be very severe and troublesome to the patient. Constipation is thought to be mediated by the effect of codeine on gastro intestinal tract smooth muscle cells. Some suggests that it is mediated by the effect on intramural nerve plexuses. Other hypothesis suggests that constipation is partly mediated by its central effect since intra ventricular injection of codeine inhibits the propulsive movements of the gastro-intestinal tract.