Addiction is the chronic, compulsive use of a drug for nonmedical reasons. It is characterized by a craving for mood altering drug effects, not pain relief. Addiction is accompanied by inappropriate behaviours, which may include denial of drug usage or illegal activity to acquire the craved drug.

A contraindication is a condition that makes a particular medication inappropriate for an individual. For example, because the body processes acetaminophen in the liver, liver disease is considered a contraindication to acetaminophen therapy.

Not all drugs are compatible with each other. A drug interaction occurs when two or more drugs are taken together and they affect each other. In some drug interactions one drug stops another from working; other interactions can make a drug much more potent. Sometimes a combination of drugs can produce toxicity.

Precautions are factors that make it risky to take a certain type of medication. For this reason it is important to discuss the use of all medications with your doctor or pharmacist.

Physical dependence is the body’s physiological adaptation to the presence of an opioid (narcotic pain reliever), leading to the development of withdrawal symptoms when the opioid is discontinued. Physical dependence is not the same thing as addiction.

Drugs can produce actions other than what we take them for; these actions are referred to as side effects. Not all drugs produce the same side effects in all people. For example, a drug may cause one person to become dizzy or develop an upset stomach, but another person taking that same medication will have no problem. It is important to report side effects to your doctor. There may be another medication that can treat your problem without causing unwanted actions.

Taking a medication such as a narcotic pain killer for a long period of time can cause your body to get used to the drug, so that you will need to keep increasing the amount of the drug you take in order to get the same level of relief. This is called tolerance.

The effects a drug has is relative to the amount of the drug that is in the bloodstream. When there is too much of a drug in the body, the level can become toxic (harmful). Toxicity can result from taking too high a dose, taking the drug for longer than it was meant to be taken for, or from a problem with the body’s ability to eliminate the drug.