A man needed to have his
levothyroxine dosage doubled when he took ritonavir/ saquinavir, and a woman possibly had a similar reaction when she took indinavir then nelfinavir. Hypothyroidism was unable to be corrected in another woman while she was taking
lopinavir/ritonavir and then nelfinavir. Another woman needed a markedly reduced dose of
levothyroxine when given indinavir.
Direct information is limited and the presence of an interaction seems to depend on the individual
protease inhibitor, how it affects glucuronidation, and how much remaining
thyroid function a patient has. Until more is known about this interaction it would seem prudent to monitor
thyroid function more closely if a
protease inhibitor is given to a patient with pre-existing
thyroid dysfunction.