3.1.1 Absorption
Orally administered ethinylestradiol (EE) and progestogens are absorbed from the small
intestine. Absorption may be affected indirectly by drugs that cause vomiting or severe
diarrhoea, chelating drugs and drugs that alter gastric pH or gut transit.
3.1.2 Metabolism
Orally administered EE and progestogens undergo extensive ‘first-pass metabolism’ in the
small intestinal mucosa and liver before reaching the systemic circulation.10,11 EE is
metabolised in the mucosa of the small intestine and in the liver, forming sulphate and
glucuronide conjugates (Figure 1).