Effects of Codeine on the Human Body
Codeine is mainly used as a pain reliever, but is also used for the relief of a non-productive cough, and as an anti-diarrheal agent. 120mg of codeine administered SC (subcutaneously, injected under the skin) provides pain relief equal to 10mg of morphine administered by the same route. Doses used to relieve cough or diarrhea range from 5mg to 30mg.
Codeine is absorbed quickly from the GI tract and it’s first pass through the liver results in very little loss of the drug. This contrasts with morphine in which over 90% of the drug is metabolized in the first pass through the liver resulting in a considerable loss of potency when administered orally. This is why codeine is a common opiate in the relief of pain, the ease of oral administration.
Codeine can be administered by many routes, this includes, SC, IM (intramuscularly), as an enema, and orally. Note, codeine can’t be administered safely by IV (intravenously) injection as it can result in pulmonary edema (fluid in lungs), facial swelling and other life threatening complications.
Codeine is converted to morphine in the brain. This of course will result in a positive result in a drug test for the opiates. It is not known whether or not the drugs heroin, morphine or codeine can be separately determined on a drug test.
Codeine is extremely addictive, as with other opiates. Withdrawal from codeine is not nearly as bad as with harder opiates such as morphine and especially heroin, but it is still unpleasant.
Some common side effects from codeine include drowsiness, light-headedness, dry mouth, urinary retention (difficulty in urination), constipation and of course, euphoria. Adverse effects can include itchiness (common), confusion, nausea and vomiting. The nausea experienced with codeine is less common and less intense than that experienced with the stronger opiates such as morphine.