Sometimes the result is drowsiness and difficulty in walking, talking, driving, and thinking. Breathing and heart rate can be depressed to dangerous levels. Some combinations of alcohol with barbiturates, tranquilizers, and prescription painkillers can be fatal. Some of the interactions may be minor and some disastrous. The consequence of the interaction is the important thing to remember.
Alcohol is primarily a central nervous system depressant.
When combined with other drugs with similar depression action on the central nervous system, an additive or synergistic effect occurs. This is the most important type of interaction between alcohol and other drugs. Whether lasting a few minutes or hours, blackouts are unpredictable but usually happen when the blood alcohol level is high. A blackout usually occurs after ingestion of large amounts of alcohol and for most social drinkers, it is a learning experience. Continued drinking patterns that produce blackouts indicate a high risk for alcohol problems.