Simvastatin 4- Levothyroxine

Chronic hepatitis was reported in a 58-year-old woman with a history of high blood pressure, hypothyroidism, diabetes, and high cholesterol. The woman had been taking 80 mg of black cohosh extract daily for 1 year along with irbesartan, levothyroxin, simvastatin, and insulin. The liver injury was initially thought to be induced by simvastatin, although discontinuation of simvastatin did not result in a reduction of liver enzyme levels (Pierard et al. 2009). 

Clinically important, potentially hazardous interactions with alfentanil, alfuzosin, alprazolam, amiodarone, amprenavir, aprepitant, astemizole, atazanavir, bepridil, buprenorphine, bupropion, carbamazepine, chlordiazepoxide, ciclesonide, clozapine, conivaptan, cyclosporine, cyproterone, dasatinib, diazepam, dihydroergotamine, ergot alkaloids, estazolam, eszopidone, etravirine, ezetimibe, fentanyl, fesoterodine, flecainide, flurazepam, fluticasone, halazepam, ivabradine, ixabepilone, ketoconazole, lapatinib, levothyroxine, meperidine, meptazinol, methysergide, midazolam, nifedipine, nilotinib, oral contraceptives, phenytoin, pimozide, piroxicam, propafenone, propoxyphene, quazepam, quinidine, ranolazine, rifabutin, rifampin, rifapentine, rimonabant, rivaroxaban, saquinavir, sildenafil, silodosin, simvastatin, solifenacin, St John s wort, tadalafil, temsirolimus, trabectedin, triazolam, vardenafil, voriconazole, zolpidem... 

A 75-year-old woman who had been stable taking levothyroxine 800 micrograms weekly for many years had a gradual increase in TSH levels and increasing tiredness after starting to take simvastatin 10 mg daily. After 4 months the levothyroxine dose was increased to 900 micrograms daily, but the patient s symptoms had not improved in 2 weeks and the simvastatin was stopped. The patient s symptoms gradually resolved, and the dose of levothyroxine was redueed baek to the previous level. ... 

Another patient, who had reeentiy started taking levothyroxine 50 micrograms daily, because of rising TSH levels, was also given simvastatin 10 mg daily. TSH levels continued to increase, so the simvastatin was stopped, and the TSH levels decreased to the normal range within 4 weeks without the need for an alteration in the levothyroxine dose. This patient was subsequently treated with pravastatin without a change in thyroid status. ... 

The authors conclude that any interaction must be extremely rare given the frequent use of simvastatin and levothyroxine. No special precautions would appear to be required on concurrent use, but bear the possibility of this interaction in mind in the event of an unexpected response to treatment. 

An isolated report describes raised serum thyroid hormone levels and evidence of thyrotoxicosis in a man taking levothyroxine with lovastatin. In contrast another isolated case report describes hypothyroidism in a woman taking levothyroxine with lovastatin. Another report describes reduced efficacy of levothyroxine in two patients taking simvastatin, one of whom was successfully treated with pravastatin. 

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