Drug interactions in users of tablet vs. oral liquid levothyroxine formulations: a real-world evidence study in primary care

Proton Pump Inhibitors Do Not Affect the Bioavailability of a Novel Liquid Formulation of Levothyroxine

OBJECTIVE

This study evaluates the impact of a representative proton pump inhibitor (PPI) (omeprazole), administered simultaneously or staggered, on the pharmacokinetics of levothyroxine (LT4) solution (Tirosint-SOL).

METHODS

This was a randomized, 3-way crossover, comparative bioavailability study in 36 healthy adults under fasting conditions. Omeprazole 40 mg delayed-release capsule was administered once daily from Day 1 to 6 (mornings, Treatment-A; evenings, Treatment-B; none, Treatment-C) to increase and stabilize gastric pH. In the morning of Day 5, a single dose of LT4 solution 600 mcg was administered. Blood samples were collected 0 to 48 hours post-LT4 administration. Noncompartmental pharmacokinetic parameters were calculated for total serum thyroxine using baseline-corrected data. Maximum concentration (Cmax) and area under the concentration-time curve (AUC0-48) were included in an analysis of variance to obtain geometric mean ratios and 90% confidence intervals.

RESULTS

For both comparisons (A/C and B/C), geometric mean ratios and 90% confidence intervals for all parameters were within the equivalence boundaries (80%-125%), indicating bioequivalence: for A/C, AUC0-48 98.98% [94%-104%], and Cmax 91.68% [87%-97%]; for B/C, AUC0-48 98.94% [95%-103%], and Cmax 94.90% [90%-100%]. Median Tmax (time associated with Cmax) was similar across treatments.

CONCLUSION

This study demonstrated that Tirosint-SOL bioavailability is unaffected by coadministration of a representative PPI, given simultaneously or staggered by about 12 hours, compared to administration of LT4 solution alone. For hypothyroid patients on PPI therapy, administration of LT4 solution may reduce variations in thyroid stimulating hormone levels related to intermittent use of acid-reducing drugs and consequently the need for dose adjustments.

Levothyroxine personalized treatment: is it still a dream?

Levothyroxine is a milestone in the treatment of all causes of hypothyroidism. From 19th century till today, Levothyroxine experienced a great advancement, from hypodermic injections of an extract of the thyroid gland of a sheep to novel formulations, known to circumvent malabsorption issue. However, the rate of patients on suboptimal therapy is still high. Current Guidelines are clear, daily Levothyroxine dosage should be calculated based on body weight. However, we are still far away from the possibility to administer the right dosage to the right patient, for several reasons. We retrace the history of treatment with levothyroxine, pointing out strengths and weaknesses of different formulations, with particular attention to what keeps us away from tailored therapy. In the age of digitalization, the pharmaceutical industry has been giving rising importance to Digital therapeutics, that are known to be effective in reaching target therapies. By combining current knowledge of hypothyroidism therapy with cutting-edge technology, we also hypothesized what could be the future strategies to be developed in this field.

Pharmacokinetics and Clinical Implications of Two Non-Tablet Oral Formulations of L-Thyroxine in Patients with Hypothyroidism

BACKGROUND

Increased knowledge of the pharmacokinetic characteristics of orally administered levothyroxine (L-T₄) has improved individualization of dosing regimens. However, up to 40-45% of patients, depending on the leading cause of hypothyroidism, are still over- or, more often, undertreated. Unintentional non-adherence to L-T₄ replacement therapy includes all situations of unintended drug-drug and drug-food interactions as well as fasting conditions that are not necessarily respected by patients.

RESULTS

In this specific context, the overall information concerning those factors with the potential to affect L-T₄ absorption refers only to tablet formulation. Indeed, this is the reason why new non-tablet formulations of L-T₄ were introduced some years ago. In this regard, the current literature review was designed to summarize pharmacokinetic, drug and food interactions and clinical data focusing on two new oral L-T₄ formulations, i.e., liquid and soft-gel capsule in healthy volunteers and patients with primary hypothyroidism. The non-tablet L-T₄ soft-gel capsules and solution have proven bioequivalence with the usual L-T₄ tablet Princeps and generic formulations. Clinical studies have suggested higher performance of non-tablet formulations than tablet in those patients with suboptimal adherence. The impact of gastrointestinal conditions and variation of gastric pH was lower with either soft gel/solution than with tablets. In addition, the extent of drug-drug and drug-food interactions remains low and of uncertain clinical relevance.

CONCLUSIONS

Pending further studies allowing one to extend the use of soft-gel/solution preparations in unselected patients, non-tablet L-T₄ formulations should be considered as a first-line choice, especially in those patients with moderate-to-high potential of suboptimal tablet performance.

Factors influencing the levothyroxine dose in the hormone replacement therapy of primary hypothyroidism in adults

Levothyroxine (LT4) is a safe, effective means of hormone replacement therapy for hypothyroidism. Here, we review the pharmaceutical, pathophysiological and behavioural factors influencing the absorption, distribution, metabolism and excretion of LT4. Any factor that alters the state of the epithelium in the stomach or small intestine will reduce and/or slow absorption of LT4; these include ulcerative colitis, coeliac disease, bariatric surgery, Helicobacter pylori infection, food intolerance, gastritis, mineral supplements, dietary fibre, resins, and various drugs. Once in the circulation, LT4 is almost fully bound to plasma proteins. Although free T4 (FT4) and liothyronine concentrations are extensively buffered, it is possible that drug- or disorder-induced changes in plasma proteins levels can modify free hormone levels. The data on the clinical significance of genetic variants in deiodinase genes are contradictory, and wide-scale genotyping of hypothyroid patients is not currently justified. We developed a decision tree for the physician faced with an abnormally high thyroid-stimulating hormone (TSH) level in a patient reporting adequate compliance with the recommended LT4 dose. The physician should review medications, the medical history and the serum FT4 level and check for acute adrenal insufficiency, heterophilic anti-TSH antibodies, antibodies against gastric and intestinal components (gastric parietal cells, endomysium, and tissue transglutaminase 2), and Helicobacter pylori infection. The next step is an LT4 pharmacodynamic absorption test; poor LT4 absorption should prompt a consultation with a gastroenterologist and (depending on the findings) an increase in the LT4 dose level. An in-depth etiological investigation can reveal visceral disorders and, especially, digestive tract disorders.

Liquid levothyroxine formulations in patients taking drugs interfering with L-T4 absorption

PURPOSE

To describe the current knowledge on thyroid hormonal profile in patients on liquid L-T4 therapy and drugs known to interfere with L-T4 absorption.

METHODS

A PubMed/MEDLINE, Web of Science, and Scopus research was performed. Case reports, case series, original studies and reviews written in English and published online up to 31 August 2022 were selected and reviewed. The final reference list was defined based on the relevance of each paper to the scope of this review.

RESULTS

The available data showed that novel levothyroxine formulations circumvent gastric pH impairment due to multiple interfering drugs such as proton pump inhibitors, calcium or iron supplements, sevelamer, aluminum/magnesium hydroxide and sodium alginate.

CONCLUSION

New formulations can be taken simultaneously with drugs interfering with L-T4 absorption, in particular liquid formulations. Softgel capsules need more studies to support these data.

Reduced effectiveness among β-lactam antibiotics: a population-based cohort study in primary care in Italy

BACKGROUND

There are few data comparing the relative effectiveness of the individual β-lactams.

OBJECTIVES

To quantify the reduced effectiveness, defined as switching to a different antibiotic being prescribed for the same indication, among new users of β-lactam antibiotics in primary care.

METHODS

A retrospective cohort study was conducted using the Health Search Database, an Italian primary care data source. Patients newly prescribed with β-lactams for a specific indication between 1 January 2013 and 31 December 2017 were identified. A switch to a different antibiotic for the same indication occurring during a 30day follow-up was the study outcome. Cox regression was adopted to assess the risk of switching between the different β-lactams.

RESULTS

Among 178 256 patients newly treated with β-lactam antibiotics, 1172 (0.65%) switched to a different antibiotic. Amoxicillin/clavulanate (co-amoxiclav: n = 104 891) and amoxicillin (n = 21 699) were the most frequently prescribed β-lactams. The other antibiotics showed significantly higher risk of switching when compared with co-amoxiclav for lower respiratory tract [e.g. ceftriaxone, hazard ratio (HR): 1.6, 95% CI: 1.2-2.0], dental [e.g. amoxicillin, HR: 4.2, 95% CI: 2.9-5.9], and middle ear infections [e.g. amoxicillin, HR: 1.8, 95% CI: 1.1-2.7]. The same results were gathered when parenteral formulations were excluded.

CONCLUSIONS

The prevalence of reduced effectiveness of newly prescribed β-lactam antibiotics was lower than 1%. Specifically, the rate of switch to another antibiotic, when it was prescribed to treat low respiratory tract, dental, and middle ear infections, was lower among users of co-amoxiclav than those prescribed with other β-lactams.

Effectiveness of ibuprofen plus paracetamol combination on persistence of acute musculoskeletal disorders in primary care patients

Background General practitioners often deal with patients suffering acute musculoskeletal disorders. Paracetamol, non-steroidal anti-inflammatory drugs, and opioids are the most prescribed medications, according to pain intensity and patient's features. Combinations of different analgesics can be adopted to enhance pain relief, but only one fixed-dose combination has been recently launched to treat acute musculoskeletal pain. Objective This study aimed to investigate the effectiveness of ibuprofen plus paracetamol (fixed-dose) combination compared to other analgesics in preventing musculoskeletal pain persistence. Setting Italian outpatients' data extracted from a national general practice database. Method A retrospective cohort study was conducted on the Health Search Database. Patients prescribed with analgesics for acute musculoskeletal painful conditions were considered (i.e., non-chronic painful conditions, identified using a query validated by two expert General Practitioners (GPs)). For each patient, the first prescription of an analgesic was defined as index date. A new GP's visit related to musculoskeletal disorders in the first 3 months following the index date was defined as "pain persistence". Main outcome measure Risk of pain persistence among users of the ibuprofen plus paracetamol combination compared to other systemic analgesics. Results Overall, 102,216 patients were treated with systemic analgesics for acute musculoskeletal disorders. Most patients were middle-aged or elderly women. 939 (0.92%) patients were prescribed with the fixed-dose ibuprofen plus paracetamol combination for a mean duration of 7.23 ± 2.68 days, mainly for low back pain and cervicalgia. Musculoskeletal pain persistence was found in 22,125 (21.65%) patients. Compared to other systemic analgesics, the ibuprofen plus paracetamol combination resulted significantly more effective in preventing pain persistence (adjusted hazard ratio 0.72, 95% confidence interval 0.61-0.85). Conclusion These findings suggest that the fixed-dose ibuprofen plus paracetamol combination might be effective in controlling musculoskeletal pain persistence.

Epidemiology of idiopathic pulmonary fibrosis: a population-based study in primary care

Idiopathic pulmonary fibrosis (IPF) is a chronic disease with unknown etiology and poor prognosis. Little is known about the epidemiology of this disease; most of the studies are limited by small and restricted cohort studies. We aim to investigate the epidemiology of IPF in the Italian primary care setting using the Health Search Database (HSD) between January 2002 and June 2017. In an attempt to define cases of IPF we adopted iterative combinations of International Classification of Diseases Ninth Revision (ICD-9-CM) and other clinical investigations according to three different operational Algorithms. Incidence and prevalence rate, according to the three Algorithms defining IPF, were calculated and the association with candidate determinants [sex, age, gastro-esophageal reflux (GERD) and smoking status] was evaluated. We identified 1,104,307 eligible patients. The prevalence rate of IPF varies between 2.6 to 24.3 per 100.000 person-year, using algorithm 1 and from 0.8 to 7 using algorithm 3. The incidence rate of IPF varies between 1.25 and 3.77 per 100.000 person-years, using algorithm 1 and from 0.10 to 1.61 using algorithm 3. The mean adjusted incidence rate ratio of IPF, using algorithm 1, is 2.33 (95% CI 2.11-2.57) per 100.000 person-years. Over the study years, the trend of prevalence was statistically significantly increasing while the incidence rate started to increase in the last 3 years. The analyses on candidate determinants showed that patients aged 61 years or older, those suffering from GERD, and former smokers were statistically significantly at greater risk of incurring IPF. To our knowledge, this is one of the first European IPF epidemiological studies conducted in primary care. The increase of the incidence rates is likely due to a growing awareness for IPF among General Practitioners, while the increase of prevalence rates may be due to an increase of survival, a result of recent advances in the diagnosis, management and therapies for the disease.

Levothyroxine Formulations: Pharmacological and Clinical Implications of Generic Substitution

Oral levothyroxine (LT4) is the standard therapy for patients with hypothyroidism. Oral LT4 is available in several formulations, including tablets, soft gel capsules and oral solution. Multiple brand-name and generic LT4 tablets are available. In the US, the Food and Drug Administration (FDA) has developed a protocol for establishing bioequivalence of LT4 formulations based on serum thyroxine (T4) levels after a single oral dose administered to healthy volunteers. This protocol has been criticized by professional endocrinology associations for using healthy individuals and ignoring serum thyroid-stimulating hormone (TSH) levels. In addition, the protocol did not initially correct for baseline T4 levels, although this was changed in a later version. There are concerns that the FDA's protocol could allow products with clinically significant differences in bioavailability to be declared therapeutically equivalent and interchangeable. Once a generic LT4 has been shown to be bioequivalent to a brand-name LT4, it may be substituted for that brand-name LT4 with no need for dose adjustment or follow-up therapeutic monitoring. Often, the substitution is made by the pharmacy without the physician's knowledge. Even small differences between LT4 formulations can cause significant changes in TSH levels. This may be a particular concern in vulnerable populations, including elderly, pregnant, and pediatric patients. Problems that can be encountered when switching between formulations or when original products are reformulated are discussed in this review. These problems include altered efficacy and adverse events, some of which can be caused by excipients. Patients should be maintained on the same LT4 preparation if possible. If the LT4 preparation is changed, TSH levels should be evaluated and, if necessary, the dose of LT4 adjusted.Funding: Merck.Plain Language Summary: Plain language summary available for this article.

Adjuvanted versus nonadjuvanted influenza vaccines and risk of hospitalizations for pneumonia and cerebro/cardiovascular events in the elderly

Background: The higher effectiveness of MF59®-adjuvanted trivalent influenza vaccine (MF59-TIV) vs. nonadjuvanted TIV in preventing influenza-related hospitalizations was found considering few influenza seasons, local and heterogeneous settings. This study evaluated the relative vaccine effectiveness (rVE) of MF59-TIV vs. nonadjuvanted TIV on the risk of hospitalization for pneumonia and cerebro/cardiovascular events across 15 consecutive influenza seasons. Research design and methods: Using Health Search Database, a case-control study was nested in a cohort of elderly vaccinated with MF59-TIV or TIV. Conditional logistic regression was used to estimate the odds ratio with 95% confidence intervals (CI) of hospitalizations potentially related to influenza in patients vaccinated with MF59-TIV or TIV. Results: Of 43,000 patients vaccinated with MF59-TIV (66.2%) and TIV (33.8%) for the first time, 103 cases of hospitalization for pneumonia or cerebro/cardiovascular events (0.11 per 1,000 person-weeks) during 15 influenza seasons were identified. The MF59-TIV was associated with a reduced risk of hospitalizations for pneumonia and cerebro/cardiovascular events vs. TIV [rVE: 39% (95% CI: 4-61%)]. Conclusions: In a 15-season cohort of elderly, MF59-TIV seems to reduce the risk of hospitalizations for pneumonia and cerebro/cardiovascular events when compared with nonadjuvanted TIV. Our findings support the recommendation for MF59-TIV in the elderly population.

Prescribing patterns of allopurinol and febuxostat according to directives on the reimbursement criteria and clinical guidelines: analysis of a primary care database

OBJECTIVE

According to American clinical guidelines, allopurinol and febuxostat may be prescribed as first-line therapy to treat hyperuricemia. However, the Italian Medicines Agency directive, called Nota 91, allows the reimbursement of second-line febuxostat in the case of failure and/or intolerance of a previous allopurinol therapy, so partially embracing European League Against Rheumatism recommendations and the British Society for Rheumatology Guideline. Such inconsistency might lead to heterogeneity among General Practitioners (GPs) in treatment of hyperuricemia. This study, therefore, aimed to evaluate the prescribing behavior of GPs in terms of compliance with Nota 91 and/or official guidelines.

METHODS

Using the Health Search Database, a retrospective cohort study was conducted to evaluate the patterns of use of allopurinol and febuxostat between 2011 and 2016.

RESULTS

In total, 44,257 and 5837 patients were prescribed with allopurinol and febuxostat, respectively. Among febuxostat users, 4321 (74%) had a previous allopurinol treatment; 92% of switches to febuxostat were related to hyperuricemia, whereas 9% of switchers presented intolerance to allopurinol; 26% of patients were prescribed with febuxostat as first-line therapy. The presence of diabetes and/or moderate/severe renal disease were statistically significant determinants of febuxostat use as first-line therapy.

CONCLUSION

Prescriptions of febuxostat were highly compliant to Nota 91. Only a sub-group of frontline prescriptions of febuxostat were mainly driven by the presence of renal dysfunction, which is able to increase the risk of allopurinol intolerance and/or inefficacy. These findings indicate that GPs' prescribing behavior for hyperuricemia is highly compliant with both regulatory directives and clinical guidelines.

Overview on the management of diverticular disease by Italian General Practitioners

BACKGROUND

Although very common in Western countries, poor epidemiological data on diverticular disease (DD) is available from the family practice.

AIMS

To evaluate the behavior of Italian General Practitioners (GPs) on approaching DD.

METHODS

Health Search Database was analyzed retrospectively.

RESULTS

On a population of 975,523 individuals, 33,597 patients had a registered diagnosis of DD ("lifetime" prevalence = 3.4%, M = 3.2%, F = 3.7%; higher values are found in females over-65 years old; low rates of complications: diverticulitis = 0.3%, bleeding = 0.002%). As risk factors, NSAIDs and ASA were taken by 14.8% and 26.5% respectively, opioids by 7.5%, corticosteroids by 5.2%; as protective factors, 30.4% were under statins and 17.7% under calcium-antagonists. Approximately 13% of patients were referred to specialists. Colonoscopy and abdominal CT were prescribed to 48.5% and to 13% of already diagnosed patients. Among DD sufferers, 27% experienced hospitalization, but only 3.4% of cases were for a DD-linked problem. Treatment included rifaximin (61%), mesalazine (14.7%), probiotics (12.4%), ciprofloxacin (7.6%).

CONCLUSION

DD has a large impact in general practice with a higher prevalence in the elderly. GPs are required to pay particular attention to risk factors both for disease development and for its complications in order to reduce the costs deriving from diagnostic procedures, referral and hospitalization.

Pharmacokinetics and Comparative Bioavailability of a Levothyroxine Sodium Oral Solution and Soft Capsule

A new formulation of levothyroxine sodium has been developed in the form of an oral solution contained in unit‐dose ampules. A study has been conducted to compare the bioavailability of levothyroxine sodium oral solution and levothyroxine sodium soft capsule in healthy volunteers under fasting conditions. The rate and extent of absorption of the new levothyroxine solution were also evaluated when administered on dilution in water or directly into the mouth without water. In each period, according to the randomization scheme, subjects were administered single oral doses of either test, as 4 × 150‐μg unit‐dose ampules, with or without water, or reference, as 4 × 150‐μg capsules in a crossover design. Thirty‐six subjects were randomized and dosed in this study; of these, 31 completed all study periods. When comparing the solution with the capsule (both products administered with water), the 90% confidence intervals for the ratio of log‐transformed values of AUC_0‐48 and C_max were within 90.00% and 111.11%, respectively, for baseline‐corrected levothyroxine. Moreover, the administration of levothyroxine oral solution without water did not affect the rate and extent of its absorption. In conclusion, levothyroxine oral solution unit‐dose ampules were bioequivalent to the levothyroxine capsule when administered with or without water. All formulations were well tolerated, with no major side effects.