Multiple factors are involved in pediatric population being under represented in clinical trials. [5] Thus therapy is based on clinical experience of the physician and extrapolation of adult data, leading to the use of drugs not labelled for use in pediatrics [6]. Additionally, they are also exposed to a high number of CSDDIs. Studies have reported multiple risk factors for DDIs, [13, 15] but to the best of our knowledge, off label drug use has not been used as risk factor for CSDDIs. Drugs that contributed to CSDDIs as well as prescribed in off label manner could lead to an increased risk of ADRs, deteriorate the condition of patient and increase the length of hospital stay. [16, 17].
Current study reported the prevalence of OL drugs and CSDDIs to be 44.5% and 25.6% respectively. A total of 91.2% patients were prescribed at least one off label drug. The results are congruent with a Serbian study which was conducted in cardiology setting and reported 47% of all the drugs prescribed were off label. [18] Another study performed in France reported off label drug prescription to be 37.6%. [19] A German study where 415 pediatric patients were assessed for off label prescriptions, reported 31% off label prescriptions in cardiovascular drugs. [20] A cross-sectional study carried out to examine off label drug utilization for antihypertensive drugs, reported 50% of drugs prescribed as off label in children. [20] The variation among different countries in prevalence of off label prescriptions is possibly due to the different design and method of studies.
The prevalence of DDIs in the pediatric cardiology ward was observed to be 52.8%, while 25.6% of the total observed DDIs were clinically significant. Another study conducted at pediatric intensive care unit of tertiary care center of Pakistan in 2017 reported 59% DDIs. Out of total DDIs, 34% were CSDDIs [9] Similarly a study in USA reported 49% of the hospitalized children had DDIs and 41% of these were clinically significant [8]. Difference in the study population and drugs may be the reason for the differences in the prevalence of CSDDIs.
Pediatric cardiac care has evolved as a distinct discipline in well-established cardiac programs in developed countries but physicians still face challenges in pediatric cardiac treatment due to presence of several factors including multiple congenital malformations, low birth weight, prematurity, intrauterine growth restriction, and CHD type in pediatric population [21] Unfortunately the epidemiology of heart failure in pediatric populations is very poorly established especially in developing countries. High prevalence of cardiomyopathies in developing regions like Pakistan is because of multiple factors in which rheumatic heart disease and poor screening program in pediatrics are most common [22]. Extension of screening in pediatrics should be considered with interest in the light of the higher prevalence of the disease and relative clarity of subclinical cardiac morbidities that could be more easily diagnosed in the clinical practice and burden of disease can be minimized in our region.
Anti-bacterial was the most prevalent therapeutic categories in cardiology ward. The reason for high prevalence of anti-bacterial drug class may be the high prevalence of respiratory infectious disease (pneumonia) present in the study population. Aspirin was the most frequently reported drug involved in CSDDIs, and was also one of the frequently prescribed off label drug. Drugs when are prescribed as OL or are involved in a clinically significant DDI pose greater risk of ADRs. Various study reported an increased risk of ADRs when a patient is exposed to OL prescriptions. [17, 23, 24] Similarly presence of clinically significant drug interactions also pose a higher risk of an ADR. A research revealed significant difference between the chldren who had ADRs with the presence of DDIs to children without ADRs in absence of DDIs [25]A Croatian study also validated this significant relationship [26].
Dose (43.35%) and indication (22.22%) were the prevalent reasons for off label drug use while a prospective study conducted in pediatric cardiology ward in Serbia also observed dose (26%) and age (21%) as the most common reason for off label drug use [18] The major problem in treatment of pediatric cardiac disorders was lack of pediatric pharmaceutical formulations of cardiovascular drugs. In pediatrics, 75% of the prescribed drugs were prepared from adult dosage forms [27].
Age group, number of prescribed drugs and off label use of drugs were found to be significant for drug interactions in univariate model while only age group and number of prescribed drugs were significantly associated with CSDDIs in multivariate model. A similar relationship has also been reported by other pediatric studies [7, 28, 29]. Off label drug use was also found to be a significant predictor for DDIs in the univariate model, and is also known to be associated with ADRs, however, it became insignificant in the multivariate model. This may be because of the inclusion of a single cardiology ward, not having sufficient patients to display a significant association. The relationship could be tested in a multicenter study in the future for better insight.
Lack of pediatric pharmaceutical formulations of cardiovascular drugs and previously mentioned notable facts emphasize that some interventions must be performed, like monitoring of plasma concentrations, laboratory tests and dose adjustments etc. Many problems exist which restrict clinical trials in cardiovascular drugs for pediatrics, including low prevalence of pediatric cardiovascular diseases as compared with adult cardiovascular disease, disease heterogeneity, lack of research infrastructure, ethical consideration in pediatric research, and difficulty in identifying appropriate clinical end points [30].
Therefore, conducting research at pediatric cardiology ward is difficult, as majority of regimens used in this population are not well documented. The decisions regarding the therapy are most often based on extrapolation from adult studies, observational data, or clinician experience. A drug used as off label and has also contributed to drug interaction should be replaced by a safer one, while suitable strategies should be introduced during the usage of these drugs.
Current research adds a new predictor for the CSDDIs especially for pediatric population. Furthermore, the study also identified common drugs prescribed in pediatric cardiology, significantly involved in CSDDIs.
4.1 Limitations
The study was conducted at a single center and limited to pediatric cardiology ward, so further multicenter studies are required to evaluate DDIs particularly in relevance to off label drug use in other pediatric departments as well.