FDA review may be limiting thyroxine supplies

OB/GYN News, Feb 15, 2002 by Mary Ann Moon

WASHINGTON -- A Food and Drug Administration ruling may be limiting supplies of thyroxine preparations, according to a fact sheet released by the American Thyroid Association at its annual meeting.

In 1997, the FDA decided that a new review was needed to ensure the safety and efficacy of these products and required every manufacturer to file a New Drug Application for each agent.

Abbott Laboratories petitioned the FDA to "grandfather" its thyroxine preparation, Synthroid, and spare it from the New Drug Approval process. Two-thirds of the 13 million Americans who take thyroxine are prescribed Synthroid, the first such preparation to be branded more than 40 years ago. Synthroid is the third most commonly prescribed drug in the United States.

But the FDA rejected Abbott's petition in April and ruled in July that any manufacturer failing to submit a New Drug Application by August would have to remove its product from the market immediately.

The FDA also ruled that any manufacturer that filed its application by August but had not yet received approval would have to start phasing the product off the market.

The phase-out procedure called for reducing distribution by a set percentage every 3 months, so distribution would fall to 60% at 1 year and production would halt by 2 years.

King Pharmaceuticals, maker of Levoxyl, and Watson Pharmaceuticals, maker of Unithroid, secured FDA approval last year.

The status of several generic thyroxine preparations, which are subject to the same withdrawal and phase-out regulations as the brand preparations, remains unknown.

Abbott Laboratories and Forest Pharmaceuticals, manufacturer of Levothroid, filed New Drug Applications in August but had not received approval at press time.

The FDA does not discuss applications it has received or the review process. The FDA will make an announcement only if and when the New Drug Applications are approved.

Judging by inquiries from patients and physicians, the ATA is concerned that some patients are already having trouble obtaining even the approved brands of thyroxine. Pharmacies may not carry all brands of thyroxine. When one brand is phased out, there may be shortages until another brand can be substituted.

"We're still researching this to determine how widespread the problem is," an ATA press spokesperson said in an interview.

The ATA supports the FDA's mandate to review and approve thyroxine preparations, but it favors expediting the review and ensuring the continued availability of these agents during the review process.

Even though patients can be switched to another thyroxine preparation safely, these products aren't interchangable, the ATA said, Any switch requires TSH testing and possible dose adjustment.

"Even the threat of interruption causes alarm, inconvenience, and cost for patients who are doing well on their current thyroid medication," Dr. Paul W. Ladenson, ATA secretary, said in a press statement. "The American Thyroid Association, the Endocrine Society, and ThyCa [Thyroid Cancer Survivors' Association] are also concerned that patients could be harmed medically if they are forced to switch from one brand to another without appropriate monitoring and, when needed, dose adjustment."