rectally
Codeine cannot be safely administered by intravenously as it may result in pulmonary oedema, facial swelling, dangerous release of histamines, and various cardiovascular effects.
It cannot be administered intranasally (snorting). Codeine free base can be smoked on the aluminum foil similarly to smoking heroin.
What are some of the common effects of Codeine addiction?
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.
Narcotics induce an "opioid analgesia" by altering the perception of pain at the spinal cord and brain. They also affect emotional responses to pain. Opioids have stimulating effects as well because they block inhibitory neurotransmitters. Repeated use of these drugs can cause long-term changes in the way the nervous system functions and incite:
