Of these, 9 suggested a hypothyroid state, with 4 hyperthyroid and 14 euthyroid. Only 27 of the 335 cases included reference to thyroid function test results. Of the 335 cases, 12 reported a recurrence of their symptoms after a second trial with the medicine concerned. Associated symptoms were mostly consistent with hypothyroidism or hyperthyroidism, and included fatigue, headache, malaise, anxiety, palpitations, pruritus, nausea, myalgia, dizziness, arthralgia, feeling abnormal, alopecia, depression, abnormal weight gain, and insomnia. The majority of reports were received from patients rather than healthcare professionals, with 47 of the cases having a healthcare professional reporter. įor the 5-year period between 1 January 2015 and 31 December 2019, the MHRA received 335 Yellow Cards reporting one or more of the terms ‘product substitution issue’, ‘condition aggravated’ or ‘drug ineffective’ with levothyroxine. Between 1 January 2016 and 31 December 2020 there were a total of nearly 260 million packs of levothyroxine dispensed against a prescription in UK retail and hospital pharmacies. Levothyroxine is one of the most commonly prescribed medicines in the UK. The MHRA has conducted a review of the available data and sought advice from the Commission on Human Medicines (CHM) as to whether any regulatory action is needed to minimise the risk of adverse events on switching between different levothyroxine products. Nevertheless, the MHRA receives reports of patients experiencing adverse events on switching between different levothyroxine products. This generic prescribing approach is supported by strict UK regulatory requirements for licensing to ensure compatibility (bioequivalence) between products. Patients may thus be changed between different levothyroxine products according to what is available at their local pharmacies, with the prescriber generally unaware of the specific product that the patient is taking at any particular time. In the UK, prescribing of levothyroxine is usually generic, with no named product specified on the prescription. Levothyroxine is authorised for the control of hypothyroidism. report suspected adverse reactions to levothyroxine medicines, including symptoms after switching products, to the Yellow Card scheme.if symptoms or poor control of thyroid function persist despite adhering to a specific product, consider prescribing levothyroxine in an oral solution formulation.if a patient is persistently symptomatic after switching levothyroxine products, whether they are biochemically euthyroid or have evidence of abnormal thyroid function, consider consistently prescribing a specific levothyroxine product known to be well tolerated by the patient.if a patient reports symptoms after changing their levothyroxine product, consider testing thyroid function.a small proportion of patients treated with levothyroxine report symptoms, often consistent with thyroid dysfunction, when their levothyroxine tablets are changed to a different product – these cases are noted in UK professional guidelines.generic prescribing of levothyroxine remains appropriate for the majority of patients and the licensing of these generic products is supported by bioequivalence testing.
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