PharmacoVig_BOS said:Heartburn management on constipation: Gaviscon before bed has been my savior.
Drug interaction alert relevant to constipation: if you take oral levothyroxine (Synthroid), GLP-1 agonists can reduce absorption due to delayed gastric emptying. My TSH drifted up after starting semaglutide.
Solution: take levothyroxine on an empty stomach, 60 minutes before any food, and have your TSH rechecked 6-8 weeks after starting or changing GLP-1 dose. My endo had to increase my Synthroid by 12.5mcg.
PeptideChemSF said:Sulfur burps on constipation — the most underrated side effect nobody warned me about.
Thank you for spelling out the reasoning rather than just the conclusion.
PharmacoVig_BOS said:Heartburn management on constipation: Gaviscon before bed has been my savior.
Gastric emptying studies and constipation: semaglutide delays gastric emptying by ~40% at steady state, as measured by acetaminophen absorption testing and scintigraphy[1].
Clinically relevant implications:
- Explains early satiety and nausea
- Affects absorption of co-administered oral medications
- Creates aspiration risk for procedures under anesthesia
- Contributes to constipation via slowed GI transit
Importantly, the gastric emptying delay attenuates with continued use (tachyphylaxis), which correlates with the transient nature of GI side effects.
[1] Blundell J, et al. Diabetes Obes Metab. 2017;19(9):1242-1251.
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Browse GL BiochemOne concrete data point for the thread. Worth stating the units and the reference range whenever you post a number here. A large fraction of the apparent disagreement in these threads is two people using different units and both being right.