Drugs and their interactions.

Small molecules with selective efficacy can be used as drugs. Drugs typically have a therapeutic dose range where the benefit from intended effects outweighs the cost of unintended (side) effects. Herein, I use case scenarios to illustrate potential advantages and pitfalls of treatment with drugs alone or in combination. Combinations of drugs may show surprising effects given the effects of individual drugs, in phenomena known as drug interactions. Drug interactions can be classified as synergistic or antagonistic, if the effect of the combination is higher or lower than expected, respectively. A better understanding of drug interactions and their relationship to phenotypes offers hope in finding drug combinations that have high therapeutic values.