Codeine effects and side-effects

Codeine is an opioid/narcotic analgesic that is typically used to reduce coughing or to relieve mild or moderate pain. It is often used in combination with other medications. However, codeine can have harmful interactions with many substances (like medications, herbal supplements, alcohol, narcotics, and so on), so it is in a person's best interest to discuss with a health care provider all other substances they are taking before beginning a prescription of codeine.
Codeine acts in the central nervous system (CNS). Opioids attach to specific opioid receptors (found in the brain, spinal cord, and gastrointestinal tract) and when this happens, opioids can effectively change the way a person experiences pain. Codeine can affect regions of the brain that influence how we perceive pleasure, which could result in an initial feeling of euphoria after taking the medication. Codeine may also produce drowsiness, cause constipation, and (depending on the amount taken) depress breathing.
More common (and much less severe) side effects of codeine may include dizziness, light-headedness/feeling faint, and nausea or vomiting. However, if anyone taking codeine begins having seizures/convulsions, severe dizziness or drowsiness, low blood pressure/slow heartbeat, severe weakness, difficulty breathing, severe mood changes, or any other alarming symptoms, s/he will want to contact a health care provider immediately.
Caution: Taking a large single dose of codeine could cause severe respiratory depression and even death. And because codeine can add to the effects of alcohol and other CNS depressants, taking an overdose of the medication (or taking it in combination with alcohol or CNS depressants) can lead to unconsciousness or death. A final word of caution, because codeine can be passed along to the baby, women who are pregnant or breast feeding should avoid this drug.
One last thing you should know is that codeine can be habit-forming. In other words, physical dependence can develop, meaning: (1) if the body adapts to the presence of codeine, withdrawal symptoms may occur if use is reduced suddenly, and/or (2) tolerance may develop meaning that higher doses of codeine are needed to get the same effects. Physical dependence is not the same as addiction; people can become addicted to codeine as well. Addiction is defined as compulsive (and often uncontrollable) drug use in spite of negative consequences. To avoid becoming addicted to codeine, it is recommended that people do not take larger doses, take it more often, and do not take codeine for longer than their health care provider suggests.
In spite of all these words of caution, codeine can be very effective and can bring great relief to those in pain when used properly.