The increase in gastric pH, the decrease in gastric emptying rate, and the slower gastric motility associated with pregnancy can affect the absorption of drugs.

The significant increase in plasma volume during pregnancy can increase the Vd of drugs, and the decrease in serum albumin can decrease the protein binding of drugs.

The increase in cardiac output in general and the renal blood flow in particular, increases the renal elimination rate of drugs such as ampicillin, digoxin and lithium during pregnancy.

Ampicillin which in primarily excreted unchanged in urine (> 80% of dose) is eliminated faster during pregnancy because of the increase in renal blood flow.

Imipenem which is a broad spectrum β-lactam antibiotic used in combination with cilastatin has significantly larger Vd in pregnant women compared to nonpregnant women.

Compared to nonpregnant women, pregnant women require higher doses of ampicillin and imipenem to adequately treat systemic infections.