Loss of antinociceptive effectiveness of morphine and oxycodone following titration of levothyroxine: case reports and a brief review of published literature.

Chronic pain management is a complex process involving numerous facets of care. Although pharmacotherapy is a part of the treatment plan for these patients, it often represents the most complex of the modalities to manage. Two chronic pain patients with loss of pain control following dosage increase in levothyroxine supplementation are presented. The authors sought to identify relationships among thyroid status, opioid pharmacokinetics, and nociceptive processing. In conclusion, well-designed human studies using pain models and controlling for thyroid status are warranted to better understand the impact this system has on pain control.