Pharmacology and Drug Interactions of Hormonal Contraceptives

Abstract

Hormonal Contraceptives come in various types and delivery systems. Short-acting reversible contraceptives have oral, injectable, transdermal skin patch and intravaginal ring preparations. Long-acting reversible contraceptives include the Intrauterine Device (IUD) or Intrauterine System (IUS) and Subdermal implants placed on the upper arm. Pharmacokinetics of the different delivery systems determine whether hormones (estrogen and/ progesterone and their analogues) act either locally or systemically affecting the rate at which they are metabolised and their overall possible effects. Hormonal contraceptives can be stopped or devices removed whenever the woman desires pregnancy. Pharmacokinetics such as dosage, metabolism and excretion of contraceptives is important in establishing the most reliable contraceptive method and managing side effects for various individuals. All these effects individually and combined, result in effective pregnancy prevention if instructions of use are adhered to. Prior to and during contraceptive use, drugs being used to prevent, treat or manage any diseases or conditions should be determined. Certain drugs have the ability to increase or decrease serum concentrations of progestins or estrogens and vice versa. Awareness of these qualities allows for the most suitable contraceptive with minimal drug-drug interaction affecting efficacy or causing adverse effects to be carefully chosen.