Serum levels of contraceptive hormones may be increased or decreased by concomitant drug use and hormonal contraceptives may themselves increase or decrease serum levels of concomitant drugs. Therefore, drug interactions should be considered when prescribing medication for women who may use hormonal contraception and could be at risk of contraceptive failure or other adverse effects. Contraceptive efficacy may be affected by both changes in pharmacokinetics and pharmacodynamics of hormonal contraceptives.
Pharmacokinetic interactions occur when one drug alters the absorption, distribution, metabolism or excretion of another, thereby increasing or decreasing its serum concentration and its effects. Pharmacodynamic interactions occur when one drug directly influences the clinical actions of another by synergy or antagonism. The recommendations should be used to guide clinical practice but…
