Metabolic tolerance occurs when liver enzymes are induced by repeated use of a drug. Cellular tolerance involves a change in the nerve cell as an adaptation to repeated use of a drug. Behavioral tolerance occurs when the individual learns to act normally despite the presence of a drug. Conditioned tolerance occurs with repeated use of a drug in a specific environment. Cross tolerance occurs when experience with one drug causes tolerance to another drug.
Tolerance can develop at different rates for the various drug effects.
Physical dependence might accompany tolerance. The body requires the drug to function normally i. The physiological imbalance and behavioral effects following withdrawal are called the withdrawal syndrome. Severity of withdrawal symptoms indicate the degree of physical dependence. Withdrawal effects are usually the opposite of those normally produced by the the administration of the drug.