Primary hypothyroidism is usually the result of Hashimoto's (autoimmune) thyroiditis, thyroidectomy, or radioactive iodine therapy. Treatment of hypothyroidism with replacement doses of thyroid hormone is usually lifelong. Levothyroxine (LT4; synthetic thyroxine; Synthroid, and others) is the drug of choice.1

In our October 26, 2015 article on drugs for hypothyroidism (Med Lett Drugs Ther 2015; 57:147), we said that levothyroxine should be taken on an empty stomach with a full glass of water 30-60 minutes (60 is preferable) before breakfast. We should have added that taking the drug consistently at bedtime, at least 3 hours after the last meal, is an alternative that some patients may find more convenient.

Primary hypothyroidism is usually the result of Hashimoto's thyroiditis, thyroidectomy, or radioactive iodine therapy. Treatment of hypothyroidism with replacement doses of thyroid hormone is usually lifelong. Levothyroxine is the drug of choice.

The equivalence of generic drugs to their brand-name precursors continues to be controversial. The last Medical Letter review of this subject (2002) concluded that well-documented therapeutic inequivalence between brand-name and FDA-approved generic drugs had not been reported. Is that still true? New data have become available for some drugs.

Primary hypothyroidism is usually the result of Hashimoto's thyroiditis, thyroidectomy for hyperthyroidism, goiter or cancer, or radioactive iodine therapy for hyperthyroidism.

Hypothyroidism is usually the result of Hashimoto's thyroiditis, thyroidectomy for hyperthyroidism or cancer, or radioactive iodine therapy. Treatment of hypothyroidism with replacement doses of thyroid hormone is usually lifelong. The drug of choice for thyroid replacement therapy is levothyroxine. Liothyronine and dessicated porcine thyroid are also marketed for this indication.

Breaking drug tablets in half is a common practice. In some cases, a lower drug dose may be as effective as a higher one, with fewer adverse effects. Sometimes tablets are split to achieve an intermediate dose between marketed strengths. When 2 tablet sizes cost the same, as they often do, splitting the larger size saves money. Is this a reasonable practice?

In preparing the Canadian edition of the September 27 issue, we noticed that the Canadian price for Synthroid is $6.40 (US $4.92) for 100 100-mcg tablets, compared to $52.70 in the US, an extraordinary 10-fold difference. Synthroid may have been reformulated in the US after the FDA in 1997 required all manufacturers of levothyroxine to file new drug applications because of concerns about the potency of various formulations, including Synthroid. The FDA approved Synthroid in 2002. Health Canada found no indication of a quality concern with Synthroid tablets in 2002, but in July 2004 it announced that levothyroxine will be regulated as a new drug there as well, and additional evidence of safety, efficacy and quality may be required.

The FDA has determined that 3 generic formulations of levothyroxine are therapeutically equivalent to brand-name formulations. Some brand-name manufacturers have objected, and endocrine organizations have expressed their concern.
See levothyroxine addendum

The media recently reported that the FDA has threatened to withdraw Synthroid from the market, alarming many physicians and patients.

When patents expire on brand-name drugs, generic formulations become available that often cost much less. Some physicians, however, hesitate to prescribe the less expensive drug because of concerns about the quality of generic formulations.