Is it safe to take muscle relaxers, such as cyclobenzaprine, during pregnancy?

Safety of Muscle Relaxants During Pregnancy

Muscle relaxants such as cyclobenzaprine should be avoided during pregnancy due to potential risks of birth defects and lack of adequate safety data in pregnant women.

Risks of Cyclobenzaprine in Pregnancy

• Cyclobenzaprine is classified as Pregnancy Category B by the FDA, indicating that while animal reproduction studies have not shown evidence of fetal harm, there are no adequate and well-controlled studies in pregnant women 1
• Recent research from the National Birth Defects Prevention Study found associations between periconceptional cyclobenzaprine exposure and increased risk of several birth defects, including:
  • Cleft palate (OR = 4.79)
  • Anorectal atresia/stenosis (OR = 6.91)
  • D-transposition of the great arteries (OR = 6.97)
  • Coarctation of the aorta (OR = 5.58)
  • Pulmonary valve stenosis (OR = 4.55) 2
• Even in large sample studies, cyclobenzaprine use during pregnancy is rare, suggesting cautious prescribing practices among healthcare providers 2

Non-Pharmacological Alternatives

• Physical therapy and appropriate exercise programs should be considered as first-line approaches for musculoskeletal pain during pregnancy 3
• Safer physical activities include stationary cycling, swimming, or aquatic exercises that reduce the risk of falling 3
• Proper body mechanics and ergonomic adjustments can help reduce musculoskeletal strain without medication 3
• Relaxation massage has shown positive effects throughout pregnancy for healthy women without complications, including reduced back and leg pain 4

If Medication Is Necessary

• If muscle relaxation is absolutely necessary, certain beta-blockers with selective β1 properties may be safer options in the third trimester compared to dedicated muscle relaxants like cyclobenzaprine 3
• Metoprolol is preferred over atenolol during pregnancy as it has a lower incidence of fetal growth retardation 3
• For any medication used during pregnancy, the lowest effective dose should be used to minimize potential risks 5

Special Considerations

• Women with certain conditions like active preterm labor, severe pre-eclampsia, or intrauterine growth restriction should avoid both muscle relaxants and strenuous physical activity 3
• Cyclobenzaprine is closely related to tricyclic antidepressants, which are known to be excreted in human milk, so caution should be exercised if administered to nursing women 1
• The drug may enhance the effects of alcohol, barbiturates, and other CNS depressants, which could pose additional risks during pregnancy 1

Warning Signs

• If muscle relaxants are used despite risks, patients should immediately stop and seek medical attention if they experience regular and painful uterine contractions, vaginal bleeding, persistent dizziness, or severe chest pain 3
• There is insufficient evidence to support the use of uterine muscle relaxant drugs for women with threatened miscarriage 6

In conclusion, given the potential risks and lack of well-controlled safety data in pregnant women, non-pharmacological approaches should be prioritized for muscle pain during pregnancy, with pharmacological interventions reserved only for cases where benefits clearly outweigh potential risks to both mother and fetus.