I am prescribed Elavil. I take synthyroid. Will it affect the medicine in my system?

Amitriptyline and levothyroxine have been given together.

Just as a caution remember Elavil (amitriptyline) and Synthroid (levothyroxine) have a minor drug-drug interaction. Exogenous thyroid (oral levothyroxine) may accelerate the onset or potentiate the action of tricyclic antidepressant effects (also depends on the dose of Elavil you are on). The mechanism and clinical significance is unknown.

However, individual cases of paroxysmal tachycardia, hypothyroidism, and thyrotoxicosis have been reported. Please get your doctor to monitor you initially at least and see your doctor if you have any bothersome symptoms.

http://www.drugs.com/drug_interactions.php