The patterns of outpatient off-label carbamazepine use and the potential impact of regulatory labelling process in Taiwan

Abstract

Background Carbamazepine has been associated with severe cutaneous adverse drug reactions (ADR). It is important for patients with these ADRs under off-label prescriptions are not eligible for drug injury relief in Taiwan. We conducted a study to depict the demography and possible factors related to the off-label carbamazepine use in Taiwan. We also explored the policy influence of carbamazepine use. Methods We used the dataset of one million randomly-sampled insured persons in the Taiwan National Health Insurance Research Database for 2002 and 2006 to conduct a cross-sectional study. With the use of a computerized clinical information system, carbamazepine prescriptions were categorized into five groups (A, B, C, D and E) according to these indications: Group A, B were defined as on-label use; group C, D and E were defined as various levels of off-label use, depending on the strength of support from the literature. A logistic regression model was conducted to find the factors related to off-label use.Results Based on the one million representative samples, 6305 and 5703 patients received 31 146 and 27 579 carbamazepine prescriptions in 2002 and 2006 respectively. In both years, nearly 43% of total prescriptions were related to on-label uses. Prescriptions from primary clinics and departments of internal medicine and psychiatry, the physician's age, and the patient's age were factors associated with higher risk of off-label carbamazepine use. Conclusions Our study echoes the highly prevalent off-label use of carbamazepine in Taiwan and adds to the rare research on this subject in the East Asian population. The carbamazepine relabelling in 2004 did not change either prescription patterns or factors related to off-label use.

Temporal trends and patterns in carbamazepine use, related severe cutaneous adverse reactions, and HLA‐B*15:02 screening: A nationwide study

“…Although new users of carbamazepine decreased dramatically over time, concerns have been raised due to very extensive off‐label use of carbamazepine found in our study, which has also been pointed out in a previous study in Taiwan . There may be several explanations for this phenomenon.…”

“…There may be several explanations for this phenomenon. First, the regulator‐approved indications for carbamazepine in Taiwan are epilepsy, trigeminal neuralgia, bipolar disorder, and diabetes insipidus, but there are many other indications supported by literature, such as peripheral neuropathy and schizophrenia . Second, the proportion of off‐label use was much lower when we analyzed not only the first prescriptions (eg, 91% in 2005 and 80% in 2014) but all the prescriptions of carbamazepine (eg, 56% in 2005 and 38% in 2014), which indicated that physicians may be unable to make definitive diagnosis upon the first carbamazepine prescriptions.…”