Table 6.

Drugs Commonly Used in Pregnancy Requiring Dose Adjustments (Estimates From the Literature)

Antihypertensives Drug	Dose Adjustment	PK/PD Alteration
Labetalol60,115,116	Increased dose or more frequent dosing may be needed	Oral labetalol clearance increased with pregnancy (1.4× at 12 wk, 1.6× at term); increased hepatic UGT1A1-mediated metabolism56,59
Clonidine61	Increased dose/shorter dosing interval may be needed	Renal clearance increased by 2×; half-life significantly decreased
Nifedipine117–121	Increased dose/shorter dosing interval may be needed	Oral clearance 4× higher half-life decreased by 50%; mechanism increased hepatic blood flow and CYP3A4 induction
Metoprolol122	Increased dose or more frequent dosing may be needed	Oral clearance 4× greater in third trimester; peak serum concentrations 12%-55%; mechanism increased hepatic blood flow and CYP2D6 induction
Anticoagulants
Acetylsalicylic acid123–125	Unknown, possibly increased dose requirement based on PK	Slower uptake, lower peak plasma concentration after single dose
Heparin46,126,127	Increased doses and/ or more frequent intervals may be needed	Peak plasma concentration 50% that of nonpregnant controls; reduced efficacy in pregnancy; ACCP recommends 10,000 U every 12 h or monitoring anti-Xa levels
Antibiotic drugs
Amoxicillin128,129	Increased dose/shorter dosing interval may be needed	Increased clearance
Ampicillin130	Increased dose/shorter dosing interval may be needed	Increased clearance
Cefazolin131	Increased dose/shorter dosing interval may be needed (keep plasma concentrations above the MIC)	Increased clearance and volume of distribution

ACCP, American College of Chest Physicians; CYP, cytochrome P450; MIC, minimum inhibitory concentration; PD, pharmacodynamics; PK, pharmacokinetics; UGT, uridine 5′-diphospho-glucuronosyltransferase.

These recommended dose adjustments of antibiotics, anticoagulants, and antibiotics used in pregnant women were obtained from an extensive review of the literature.