The incidence of adverse drug reactions among hospitalized patients during the 5-year period of this study was 0.81%, which was relatively low compared with other studies
[21–23]. First, this retrospective study was based on a spontaneous reporting and monitoring system, where underreporting by healthcare workers is a possibility. Although spontaneous reporting is the most widely used method for routine monitoring of ADRs
, it cannot guarantee that a particular adverse event is a true ADR. Second, it is possible that hospitalized patients affected by ADR were not included in the study. Third, the ADR definition in China could be somewhat different from the definition in other samples studied
[25, 26]. The Chinese definition did not include harmful reactions from normal doses of eligible drugs administered for medication. Thus, this definition excludes adverse events due to drug quality, administration with no indications, and off-label use.
This study showed that the incidence of adverse reactions of female patients was significantly higher than that of male patients, which was inconsistent with the adverse reactions study carried out by Agnes Chan in Taiwan
. Zhang et al.
 retrospectively analyze 1001 cases of ADRs/events induced by traditional Chinese medicine injections and find that the incidence rate in female patients was higher than that in male patients. In the retrospective study conducted by Jiang and Kuang
, the incidence of severe ADRs was also higher in women than it was in men. This result may be because TCM injections, used in many hospitals in China, are more commonly administered to women than men
. The other reason may be related to the different sensitivity levels and metabolic processes in men and women. Our results are consistent with Lee’s research finding that adverse reactions are significantly higher in patients more than 61 years than in other age groups
. Similar to other researchers in China
[32, 33], our study showed that the most common drugs involved were antimicrobial drugs. However, Jimmy Jose et al. show that the most common ADRs in 2006 were antineoplastic agents, antiepileptics and antibiotics ranked only third
. In China, more than 60% of inpatients in hospitals receive antibiotics. This may be due to the widespread clinical use of antimicrobial drugs.
However, developing countries have witnessed a growing number of ADR studies, following the damaging effects of the disease on the socioeconomic progress of those countries. A prospective analysis of 18,820 hospitalized patients was carried out in the UK
. The result showed that 1225 hospital admissions related to an ADR, showing a prevalence rate of 6.5%, with ADR directly leading to admission in 80% of the cases. The median bed stay was 8 days, accounting for 4% of the hospital bed capacity. The projected annual cost of such admissions to the NHS is £466 million (€706 million, $847 million). The results of a prospective study in France showed that hospitalization costs per ADR patient were about € 11,357.00
. This study found that the total socioeconomic loss from the 2739 cases of ADR was ¥817401.69 and that the cost per ADR patient was approximately ¥298.43. This cost is far below the level of developed countries, which may reflect the lower medical care and drugs charges in China. For these calculations, the RMB exchange rate against the US dollar is approximately 6.061, while the euro exchange rate is approximately 8.197
. The indirect costs were far less than the direct costs because chaperone charges and intangible losses were not included in the data. Therefore, the true value might be far greater than the calculated value in the present study.
The longest period of hospitalization for the most serious ADR case was 32 days, the shortest period was 2 days, and the average was 10.8 days. The highest payment was ¥39,873.78, and the lowest was ¥251.13. Although severe cases were comparatively few, direct costs accounted for 53.14% of the total loss from direct costs. This should be a focus area for future research. The costs of the two groups were significantly different, indicating that drug administration and treatment should be withdrawn promptly after an ADR occurrence, because most ADRs can be cured by withdrawal of the suspected drug
. To reduce and control serious ADR incidence, we require detailed knowledge of the patient’s history regarding food and drug allergy, smoking and drinking, and disease and medication. In addition, we also need to strengthen drug monitoring, especially for patients with allergic conditions. This would greatly reduce the associated costs, and the economic burden on the individual patient, the health-care sector, and medical institutions. At the same time, we can avoid or control ADR costs by identifying which of the ADR-related costs are relatively greater. This would be the topic of a future research. There is also a great cost difference between the two groups, suggesting that the occurrence of ADRs should promptly occur after withdrawal and treatment. Moreover, the reduction and control of the high ADR rate can greatly reduce costs, both for the patient and for the health department, thus mitigating the economic burden of medical institutions. Therefore, how to optimize ADR social costs is the most important issue.
As shown in Table
2, the proportion of Medicare payments (in China, people who pay medical insurance on time are covered by Medicare) increased with the reduction of medicine costs as a proportion of direct costs. This shows that drugs used for the treatment of ADRs were largely outside the scope of Medicare, which caused more ADRs. The higher the proportion of drug costs, the heavier the personal burden. Because inspection costs increased in groups B, and the proportion of drug costs decreased, the proportion of Medicare payments increased. However, since drug choice policies and number of patients covered by Medicare differ across hospitals, the actual proportions are not consistent with those in this study. According to the current ADR definitions and relief systems in our country, personal injury and economic loss caused by ADR would have to be borne by patients in most cases, though they could get a certain amount of health insurance compensation. However, because health insurance coverage is limited at present, the number of insured and amount of compensation are inadequate.
With price reforms in the current health system under way, the overall direct economic ADR losses of our hospitals will decrease by 10.54%. Therefore, drug price reduction would not only alleviate the problem of the high medical treatment costs but also help reduce the direct economic losses caused by ADRs.
The ADR evaluation of this study were similar to those reported by most domestic studies. However, the study focused on a single district. Cost estimates of multi-center studies would greatly enhance credibility. We hope the ADR monitoring departments of hospitals would initiate efforts to provide an economic basis for the establishment of effective ADR relief measures in China.