In ecology, commensalism is a class of relationship between two organisms where one organism benefits without affecting the other. It compares with mutualism, in which both organisms benefit, amensalism, where one is harmed while the other is unaffected, and parasitism, where one benefits while the other is harmed.n ecology, commensalism is a class of relationship between two organisms where one organism benefits without affecting the other. It compares with mutualism, in which both organisms benefit, amensalism, where one is harmed while the other is unaffected, and parasitism, where one benefits while the other is harmed.
Drug interactions also may occur when two drugs that have similar (additive) effects or opposite (canceling) effects on the body are administered together. For example, there may be major sedation when two drugs that have sedation as side effects are given, for example, narcotics and antihistamines.
Adverse Drug Reactions. Adverse drug reaction (ADR, or adverse drug effect) is a broad term referring to unwanted, uncomfortable, or dangerous effects that a drug may have.diosyncrasy is an imprecise term used to classify unexpected ADRs that are not dose-related or allergic. They occur in a small percentage of patients given a drug. Idiosyncrasy has been defined as a genetically determined abnormal response to a drug, but not all idiosyncratic reactions have a pharmacogenetic cause.