When drugs increase each others effects when taken together the interaction is called?

Drug-Drug Interactions

Pharmacokinetic and pharmacodynamic properties of drugs may be altered when ≥2 drugs are administered to a patient [Table 73.6]. Interactions largely occur at the level of drugmetabolism but may occur at the level of drugabsorption [e.g., inhibition of intestinal CYP3A4 activity by grapefruit juice or St. John's wort and consequent reduction in presystemic clearance of CYP3A4 substrates], distribution [e.g., displacement of warfarin plasma protein binding by ibuprofen with consequent increased hemorrhagic risk], or elimination [e.g., inhibition of ATS of β-lactam antibiotics by probenecid]. Also, drug-drug interactions may occur at the level of thereceptor [through competitive antagonism]; many of which are intentional and produce therapeutic benefit in pediatric patients [e.g., antihistamine reversal of histamine effects, naloxone reversal of opiate adverse effects].

Drug interactions may also occur at a pharmaceutical level as a result of a physicochemical incompatibility of 2 medications when combined. Such interactions generally alter the chemical structure of one or both constituents and thereby renders them inactive and potentially dangerous [e.g., IV infusion of crystalline precipitate or unstable suspension]. Ceftriaxone should be avoided in infants