Hypothyroidism (HoT) treatment involves lifelong thyroxine replacement therapy and regular monitoring. The objective of this study was to assess the impact of clinical pharmacist (CP) intervention in managing drug-related problems (DRPs) on outcomes among hypothyroid patients receiving levothyroxine (LT4) therapy.

The first choice in the treatment of hypothyroidism (HoT) is replacement therapy with levothyroxine (LT4). Factors other than the use of the drug are as crucial as the use of LT4 at the right time and in the right way. Drugs used by patients other than LT4, comorbidities, diet, age, and weight of the patient also affect the benefit seen from LT4 treatment.

LT4, which has a narrow therapeutic index, may cause drug-related problems (DRP) such as non-adherence to treatment, the timing of drug use, inappropriate use of the drug, inadequate therapeutic dose, duration of treatment, inadequate monitoring of treatment and potential drug-drug interactions (pDDI). In a study conducted in a hospital in India, DRP encountered during treatment with narrow therapeutic index drugs were compared with DRP encountered with other drugs. It was reported that DRPs were associated with pDDIs, adverse effects, dose overdose, dose underdose, untreated indications, inappropriate drug use, unnecessary drug use, and patient-related factors. In the study in which LT4 was also included, the rate of DRPs to narrow therapeutic index was 22%, and the rate of DRPs to other drugs was reported to be 8%. In a study documenting the interventions of pharmacists in hospitals in Germany, the interventions made between 2009 and 2012 were analyzed; LT4 was one of the ten drugs with the highest number of problems, and half of these problems were drug interactions and the inadequate therapeutic dose in patients with organ failure.

Aluminum hydroxide, bile acid secretagogues, calcium polystyrene sulphonate, sodium polystyrene sulphonate, calcium salts, iron preparations, multivitamin supplements containing iron, lanthanum carbonate, sevelamer, magnesium salts, orlistat, and raloxifene cause D-level drug interactions with LT4. In the concomitant use of calcium salts with LT4, it is observed that LT4 absorption and, consequently, therapeutic effect decreases [8,9]. In a systematic review of the concomitant use of LT4 and proton pump inhibitors (PPI) in hypothyroid patients with dyspepsia, gastroesophageal reflux, or peptic ulcer, a statistically significant increase in thyroid-stimulating hormone (TSH) levels was observed.

Since the therapeutic index of the LT4 drug is narrow, it emphasizes the importance of adherence to the drug in reaching ideal TSH levels. Medication adherence is a dynamic process closely linked to treatment outcomes in patients with chronic diseases. Very few studies exist on LT4 treatment and patient adherence to treatment. In their study, Yavuz et al. emphasized that almost half of HoT patients had serum TSH values outside the reference range despite receiving LT4 treatment and that adherence with LT4 treatment was one of the most critical determinants in reaching target TSH levels.

Inclusion Criteria:

1. A confirmed diagnosis of Thyroid Disease (ICD-10 codes: E03.9)
2. Patients visited the endocrinology diseases outpatient clinic
3. Being 18 years or older.
4. Patients who could be evaluated by the clinical pharmacist for at least 24 hours within the intervention group.

Exclusion Criteria:

1. Being under 18 years old.
2. Lost follow up in 30th day after thyroid disease.