07 Jun 08 Constipation

The popular painkiller codeine can be ineffective or, worse, cause serious reactions if you are among those people whose bodies do not process the medication properly.

The liver converts codeine into morphine using the enzyme CYP2D6, a process that causes pain relief in most people. However, genetic differences in some people cause either too much or too little of the enzyme to be produced, resulting in less than pleasant results, reports Public Citizen, a national, nonprofit consumer advocacy group, in its June Worst Pills, Best Pills newsletter.

People whose liver’s produce higher than normal CYP2D6 levels convert more of the codeine into morphine — a situation that could cause excessive sedation, severe constipation and other side effects. While this only occurs in about 4 percent of Caucasian North Americans, prevalence is much higher in people from Greece and Portugal (10 percent), Saudi Arabia (20 percent) and Ethiopia (30 percent).

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