The present prospective study carried out over a 6 week period in a tertiary referral center among adult patients showed that ADRs accounted for 3.84% (265/6899) of patients presenting to the ED. Of these 141 were admitted and thus 53.21 % (141/265) of total patients presenting to the ED with ADRs were hospitalized. At an average cost of USD 150 per patient hospitalized, they also constituted a significant economic burden.
Several studies carried out in different parts of the world have also yielded more or less similar results. The present study modeled on the study by Pirmohamed et al done in the United Kingdom had similar findings. [11
] Their study found 6.5% of ADRs causing admissions, as against our finding of 6.89%. Dormann et al evaluated the economic impact of readmissions and ADRs in internal medicine. [12
] ADRs were found to cause hospitalization in 6.2% of first admissions and in 4.2% of readmissions. Fattinger et al in their study in two Swiss departments of internal medicine found ADRs to account for 3.3% of all hospitalizations. [13
] In the present study, the mean duration of hospitalization ranged from 5–7 days while Pirmohamed found the hospitalization to range from 4–18 days. The latter also found a larger number of definite and potentially avoidable ADRs compared to our study (72% versus 59.62%). The study by Dormann found 44.3% of ADRs to be preventable using the Schumock algorithm.
A comparison of deaths due to ADRs showed that while we had 0.83% of hospitalized patients dying because of ADRs, the study by Pirmohamed had 0.15% of hospitalized patients dying of ADRs. The study by Lazarou had 0.14% deaths that could be attributed to ADR related admissions. These differences could perhaps be due to the type of hospital, nature of disease and thus drugs prescribed and perhaps inter country differences in susceptibility.
The drawbacks of our study include the short duration (6 weeks), restriction to the medicine ED only; identification of ADRs by one senior physician only at any given time (who was on duty during rotation shifts in the ED), restriction of the study only to adults and calculation of costs based on duration of hospitalization only, which could give an underestimate of the costs associated with treating ADRs. Causality assessment was done at the point of presentation to the ED and was not changed subsequently. Thus 35 "possible" ADRs where other factors could account for the reaction were also included in the final analysis. Also, causality assessment was done independently by physicians on duty and their assessments may not have been similar to one another. [14
A similar study by Sanchez Cuervo et al, albeit retrospective and carried out over a 1 year period in Spain showed some differences among the type of drugs causing ADRs in the hospital's ED [15
] While we found anti-tubercular drug induced hepatotoxicity, chloroquine gastritis and warfarin toxicity to be the common ADRs, they found insulins, diuretics, digoxin and oral anti diabetics to be the common causes of ADRs. For a country like India anti tubercular toxicity could have additional ramifications like the problem of multi drug resistance and exposure to potentially more toxic second-line agents. Wu et al evaluated outpatient ADRs leading to hospitalization and found that anti-diabetics, anti-convulsants, anti-coagulants, beta blockers and ACE inhibitors to be the common causes of ADRs. [16
] Both studies also found that ADRs occurred in older patients, while we found the mean age of patients with ADRs in our study to be 40 years.
Ayani I et al studied the economic burden in Spain of the minimum direct costs to the public health system of diagnosing and treating patients in an ED with a suspected ADR using the WHO definition of an ADR in a single month. The cost amounted to 42,732 Ecus and considering that 40% of ADRs were avoidable, they proposed that if pharmacovigilance activities included cost analysis, significant savings would result. [17
] The study by Wu et al calculated the mean cost of treating an ADR per patient to be USD 9491 with 50% of this cost being the hospitalization or room charges alone. We included in our study the hospitalization or room/bed charges only as we decided to restrict the economic perspective to the hospital only. Our hospital being a public hospital caters to the lower socio-economic strata and hence costs would be different from that of a private hospital. If we assume that similar to the study by Wu et al, these represent only 50% of the total costs, the economic burden of ADRs would be considerable. Also, we found approximately 59.62% of ADRs in our study to be avoidable or potentially avoidable. This is similar to the findings of a meta-analysis where the rate of preventable ADRs was found to be 59% (inter quartile range 50–73%). [18
] If these are minimized, it would lead to considerable savings.
In conclusion, ADRs are an important cause of visits to the hospital emergency department as well as an important cause of admission and thus a significant economic burden. It is likely that many of them particularly the avoidable and potentially avoidable ones may be minimized by patient and physician education and better prescribing practices and thus lead to considerable cost savings.