Monday Pharmaceutical Mystery: March 30

Why is guaifenesin being used for fertility?

As you are in the middle of verifying a large stack of prescriptions in baskets, a young couple walks up to you. The female patient asks if she can speak to you in private. You step over to the consultation window and she asks, “Can you help me find the Mucinex that is used to help women get pregnant? All I see are the ones used for coughing.”

Puzzled, you mention that Mucinex is usually used for a phlegmy cough, and try to get to the bottom of it—maybe she is confused? You ask some questions, and she takes out a piece of paper written on letterhead from her OB/GYN. Sure enough, her doctor has recommended Mucinex.

Mystery: Why is Mucinex being used for fertility?

Solution: Mucinex, which contains the expectorant guaifenesin, is sold over the counter to help thin and loosen mucus in patients with a productive cough. There is anecdotal data, dating back to the 1980s, of Robitussin (guaifenesin) being used to improve male and female infertility. The mechanism by which guaifenesin improves fertility is not well understood, but it appears to improve viscosity of the cervical mucus.1

In an investigation published in 1982, 40 couples with a minimum of 10 months of infertility were studies. The women took guaifenesin 200 mg TID from cycle day 5 until ovulation. After analyzing the results, the study authors concluded that guaifenesin may improve cervical mucus and improve fertility.2

If a patient is looking for Mucinex for this purpose, it is important to help the patient select the correct product with guaifenesin only, so the patient does not accidentally select a combination product. A combination product would lead to unnecessary ingredients and the potential of increased adverse effects, and drug-drug or drug-disease state interactions.


  • Means, G. et al. Guaifenesin and increased sperm motility: a preliminary case report. Int J Gen Med. 2011; 4: 13—14. doi: 10.2147/IJGM.S14585 Published online December 20, 2010.
  • Check, J. et al. Improvement of cervical factor with guaifenesin. Fertility and Sterility, Vol. 37, No.5, May 1982.