Symptoms of overdose on opiods like codeine include constipation, slow breathing, seizures, dizziness, weakness, confusion, tiredness, cold and clammy skin, small or constricted pupils, loss of consciousness, coma and possibly death!
To experience the effects of codeine, the human body must convert the drug to morphine. The effects of codeine start 10 to 30 minutes after ingestion, peak within one to two hours, and may last four to six hours, depending on how much is taken. Within two to three weeks of repetitive use, a physical and psychological addiction may develop. Misuse will lead to an apathetic, dulling-type effect, a lack of co-ordination and dulled responses.