Probable interaction between levothyroxine sodium and thyme (Thymus vulgaris), about a case report

Abstract

Thyme (Thymus vulgaris) is often used thanks to its anti-infectious properties to treat seasonal influenza. Some patients use it in conjunction with their conventional treatment, which can expose them to adverse effects or interactions. A case of probable pharmacokinetic interaction of levothyroxine and thyme is described. This is a case of 52-year-old woman admitted to the toxicology department in January 2024 after a phytovigilance questionnaire. The patient had a treatment for hypothyroidism consisting in levothyroxine sodium with a daily dose of 150 µg, but she showed palpitations following the taking of a T. vulgaris tea to treat her seasonal flu. She reported that the symptoms disappeared by reducing the doses of T. vulgaris. The score of the probability scale of the interaction was 6, so a probable interaction may occur in patients with thyroid disorders and taking levothyroxine sodium concomitantly with T. vulgaris.