Background: The data on the prevalence of a lactating mothers’ drug use is minimal.

Objective: To find the prevalence of the lactating mothers’ drug use and the associated factors.

Material and Method: The subjects were postpartum women who delivered at HRH Princess Maha Chakri Sririndhorn Medical Center in Nakhon Nayok Province during the period from September, 2016 to January, 2017. Two hundred and twenty subjects were interviewed about their drug use including the type, duration of use, source of the drugs, breastfeeding advice received, breastfeeding data and demographic data from home visits at the first month postpartum. The prevalence of the lactating mothers’ drug use and the associated factors were analyzed by percentage, t-test, Chi-square, prevalence rate ratio and a 95% confidence interval.

Results: The prevalence of the lactating mothers’ drug use was 31.4%. The most used drug during breastfeeding was ‘herbal health tonic for women’ (79.7%) at the first month postpartum. Most of the mothers bought drugs from pharmacies and were not advised about the drug’s use during breastfeeding. The associated factors of drug use were an educational level of lower than a high school education (prevalence rate ratio 2.26, 95% CI 0.98 to 5.19) and delivery by vaginal delivery (prevalence rate ratio 1.91, 95% CI 1.27 to 2.88).

Conclusion: Mothers often used ‘herbal health tonic for women’ during breastfeeding. It is likely to have negative effect on breastfeeding and the newborns’ health. Therefore, adequate evidence-based information about the drug’s use should be supported by health professionals and pharmacists. This includes establishing a social campaign.

Keywords: Lactating mother, Drug use, Breastfeeding