From the Guidelines
Phentermine can cause constipation as a side effect, as reported in the most recent study from 2022 1.
Phentermine Side Effects
Phentermine is an appetite suppressant medication used for weight loss that works by stimulating the central nervous system and increasing levels of norepinephrine in the brain. This stimulant effect not only reduces appetite but can also slow down intestinal motility, leading to constipation in some patients.
Managing Constipation
Other digestive side effects may include dry mouth, which can worsen constipation by reducing fluid intake. If you experience constipation while taking phentermine, it's essential to:
- Stay well-hydrated by drinking plenty of water
- Increase dietary fiber intake through fruits, vegetables, and whole grains
- Maintain regular physical activity to help stimulate bowel movements Over-the-counter stool softeners may provide relief if needed, but persistent constipation should be discussed with your healthcare provider, as they might recommend adjusting your phentermine dosage or prescribe a mild laxative. Never adjust your medication dosage without medical supervision, as noted in a previous study from 2017 1.
From the Research
Phentermine and Constipation
- Phentermine is an anorexiant used for weight loss, and its side effects have been studied in various clinical trials.
- According to a study published in 2011 2, constipation was reported as an adverse event in patients taking phentermine plus topiramate, with an incidence of 6% in the placebo group, 15% in the low-dose group, and 17% in the high-dose group.
- Another study published in 2013 3 also reported constipation as a common side effect of phentermine/topiramate controlled-release, along with other adverse events such as paresthesia, dysgeusia, dry mouth, and insomnia.
- There is no direct evidence from the other studies 4, 5, 6 that specifically addresses the question of whether phentermine can cause constipation, although they do discuss various aspects of phentermine use and its effects on the body.
- Overall, the available evidence suggests that constipation is a potential side effect of phentermine, particularly when used in combination with other medications like topiramate.