Dangerous Drug Combo

Thyroid Hormone and Proton Pump Inhibitors

Thyroid supplementation is extremely common. Some frequently used drugs, including proton pump inhibitors (PPIs), can interfere with thyroid hormone absorption, causing patients whose disease was previously well-controlled on a thyroid hormone to develop hypothyroidism.

The interaction between levothyroxine and omeprazole in patients with impaired gastric acid secretion requires an increased dose of oral thyroxine, which suggests that normal acid secretion is necessary for effective oral absorption of thyroxine. Patients with hypothyroidism who are euthyroid and on levothyroxine may need thyroid function testing after initiation of a PPI, especially if symptoms of hypothyroidism emerge. And those with impaired gastric acid secretion may require an increased dose of levothyroxine to keep the thyroid-stimulating hormone level within range.

The product labeling for levothyroxine recommends that it not be administered simultaneously. If concurrent use is necessary, administration of the agents should be separated by 4 hours.