Analgesics in Pregnancy: An Update on Use, Safety and Pharmacokinetic Changes in Drug Disposition.

ABSTRACT

BACKGROUND: Although medications should only be prescribed in pregnancy if benefits to the mother outweigh the risk to the fetus, drug use in pregnancy especially prescribed and over-the-counter analgesics, is very common. OBJECTIVE: The objective of this review is to present an update on known changes in analgesic disposition in pregnancy caused by pharmacokinetic mechanisms. METHOD: Herein, we discuss a wide range of medical, biomedical and scientific literature that includes reports from the fields of dentistry, general medicine, obstetrics and gynecology, pharmacology and toxicology to provide an update on the use (including indications, contraindications and concerns) of major classes of analgesics during human pregnancy. RESULTS: Over 50% of analgesics are in pregnancy category C, and even more category D specifically in the third trimester. Changes in renal filtration, cardiac output, plasma protein concentration and plasma volume particularly affect analgesics and dose adjustments may be necessary to maintain therapeutic concentrations in pregnant woman, and/or to protect the developing fetus. CONCLUSION: Analgesics are one of the most frequently used drug classes in pregnancy. More than 60% of women self-report using analgesics while pregnant, both prescribed and by self-medication. For the majority of analgesics available (excepting acetaminophen and the NSAIDs, and to a lesser extent certain opioids), good prospective clinical trials documenting pharmacokinetic changes do not exist. More research is needed in both the scientific and clinical community to understand the risks and benefits of analgesic use in pregnancy, particularly as prevalence is rising.