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Liquid formulations of levothyroxine offer the possibility of allowing patients with hypothyroidism to take their medication with meals or coffee and skip the currently recommended 30- to 60-minute waiting period before doing either, new data suggest.

Because food, coffee, and certain medications can interfere with intestinal absorption of levothyroxine (also known as LT4), current guidelines recommend that the drug be taken in a fasting state, typically 30 to 60 minutes before breakfast. However, compliance may be difficult for some patients.

Now, long term synthroid side effects a potential solution may come from new evidence that liquid levothyroxine formulations that bypass the gastric dissolution phase of absorption may mitigate the interference with food and coffee.

Findings from two bioavailability studies showing no difference in comparisons of Thyquidity (levothyroxine sodium oral solution, Vertice Pharma) with or without waiting periods before consuming coffee or a high-fat meal were presented at ENDO 2022, the annual meeting of the Endocrine Society, by Vertice Pharma Medical Director Kris Washington, PharmD.

And just last month, similar data were published in Thyroid for another levothyroxine oral solution, Tirosint-SOL (IBSA). No difference in pharmacokinetic properties were found with this product with a shorter versus a longer waiting period before consuming a high-fat meal.

Liquid Thyroxine May Be Less Affected by Food/Drink but Is Expensive

Both products have been approved by the US Food and Drug Administration (FDA), but current labeling for both still calls for a 30- to 60-minute waiting period between taking the medication and eating or drinking. Thyquidity is an oral solution of 100 µg/mL levothyroxine sodium that has been shown to be bioequivalent to one of the most popular branded levothyroxine tablets, Synthroid (AbbVie), under fasting conditions. Tirosint-SOL is also an oral solution that comes in 15 different dosage ampules.

“It is important to note that while these findings are exciting and encouraging we do want you to continue to follow the current FDA-approved label for Thyquidity recommending that it be taken on an empty stomach 30 to 60 minutes prior to breakfast and that patients continue to follow all other label instructions,” Washington said during a press briefing at ENDO.

When asked by Medscape Medical News whether the new data would be submitted to the FDA for a possible amendment to this message, she replied: “We’re still discussing that. We’re exploring all options…This is fairly new data…It makes sense and certainly solves a lot of the challenges for people who can’t swallow or don’t choose to swallow, or the challenges of splitting or crushing with tablets.”

Asked to comment, Benjamin J. Gigliotti, MD, a clinical thyroidologist at the University of Rochester, New York, told Medscape Medical News: “Liquid levothyroxine has the potential to be a clinically useful formulation,” noting that these recent data corroborate prior findings from Europe and elsewhere that liquid levothyroxine is absorbed more rapidly and thus may be less impacted by food or beverages.

However, Gigliotti also pointed out, “I don’t think malabsorption is a major contributor to suboptimal treatment because if [patients] malabsorb the hormone, we typically just increase their dose a little bit or ask them to take it separately, and that works just fine for most people.”

And the higher cost of the liquid products is a major issue, he noted. 

A quick search on GoodRx shows that the lowest price of Tirosint-SOL is $115.52 for a 1 month supply and Thyquidity is $181.04/month. “In the few patients where I tried to obtain Tirosint-SOL, it was not covered by insurance, even with a prior authorization,” Gigliotti commented.

In contrast, generic levothyroxine tablets are about $4/month, while a common brand name of levothyroxine tablets are $47.81/month.

“Until these liquid formulations are more widely covered by insurance for a reasonable copay, or come down in price compared to generic levothyroxine tablets, most of my patients have voiced that they’d rather deal with the inconveniences of a tablet compared to higher medication cost, especially with rising economic insecurity imposed by the COVID-19 pandemic and recent world events,” Gigliotti said.

Bioequivalence With Shorter Versus Longer Waits Before Coffee/Breakfast

The Thyquidity coffee study was a single-center open-label, randomized, crossover study of 40 healthy adults randomized after a 10-hour overnight fast to 600 µg Thyquidity with water under fasting conditions or to the same dose given 5 minutes prior to drinking an 8-ounce cup of American coffee without milk or sweeteners. After a 40-day washout period, the same participants received the other treatment.

Mean serum thyroxine (T4) concentrations over 48 hours were nearly identical, demonstrating comparable bioavailability. Pharmacokinetics parameters, including area under the curve (AUC) and Cmax, were also comparable for both groups. The geometric least square mean ratios for baseline-adjusted LT4 were 96.0% for Cmax and 94% for AUC. And the corresponding 90% confidence intervals fell within the 80% to 125% FDA acceptance range for absence of a food effect on bioavailability, said Washington when presenting the findings.

There was one adverse event, a decrease in blood glucose level, which was deemed to be mild and unrelated to study treatment. No deaths, serious adverse events, or discontinuations due to adverse events were reported. There were no significant changes in vital signs or on ECG.

In the second Thyquidity study of 38 healthy adults, after a 10-hour fast, the same doses were given 10 or 30 minutes prior to the consumption of a 950-calorie standardized high-fat breakfast.

Again, over 48 hours, mean serum T4 levels were comparable between the two groups. The geometric least squares mean ratios for both AUC and Cmax for baseline-adjusted LT4 were 88.7% and 85.1%, respectively. Again, the corresponding 90% confidence intervals fell within the FDA’s noninterference definition, again demonstrating lack of a food effect on bioavailability, Washington noted.

Four adverse events were reported in three participants, with three deemed to be possibly related to the medication. All were isolated lab abnormalities without clinical symptoms and deemed to be mild. Three were normal on repeat testing.
There were no deaths or serious adverse events or study discontinuations for adverse events and no significant findings for vital signs or on ECG.

Similar Findings for Tirosint-SOL But Longer-Term Studies Needed

The recently published Tirosint-SOL study included 36 healthy volunteers randomized to single 600-µg doses of the LT4 oral solution after a 10-hour fast, either 15 or 30 minutes before eating a standardized high-fat, high-calorie meal. Mean serum total thyroxine concentration profiles were similar for both the 15- and 30-minute waits, with similar AUCs.

Geometric mean ratios for AUCs at 48 and 72 hours were 90% and 92%, respectively, and the 90% confidence intervals fell within the 80%-125% FDA boundaries, suggesting similar exposures whether taken 15 or 30 minutes before a meal.

Senior author Francesco S. Celi, MD, chair of the division of endocrinology, diabetes, and metabolism at Virginia Commonwealth University, Richmond, told Medscape Medical News: “There is an interest in providing more opportunities for patients and improving adherence to the medication…Whatever makes life a bit easier for patients and results in a more predictable response to treatment means down the road there will be fewer visits to the doctor to make adjustments.”

However, he said that in addition to the cost and reimbursement issue, all of these studies have been short term and not conducted in real-life settings.

“Another question is what happens if the patient goes on low-dose LT4? The studies were conducted on much higher pharmacologic doses. But at least from a safety standpoint, there’s no specific concern.”

Washington is an employee of Vertice Pharma. Celi has received unrestricted research grants and worked as a consultant for IBSA. Gigliotti has reported no relevant financial relationships.

Thyroid. Published online May 23, 2022. Full text

ENDO 2022. Presented June 11, 2022.

Miriam E. Tucker is a freelance journalist based in the Washington, DC, area. She is a regular contributor to Medscape, with other work appearing in The Washington Post, NPR’s Shots blog, and Diabetes Forecast magazine. She is on Twitter: @MiriamETucker.

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