Several factors prompted the need for a pharmacoeconomic evaluation of IC and MEM. These included an institutional review of antimicrobial restriction and concerns about usage and costs. Most importantly, interchanging MEM with IC was thought to be able to lead to a cost saving of more than two million Saudi Riyals, as the acquisition costs of IC were noted to be less than those for MEM (SAR70.4 versus SAR 151.26 per vial). In addition, published pharmacoeconomic evaluations are limited in Saudi Arabia (Al Aqeel and Al-Sultan, 2012). To our knowledge, no published pharmacoeconomic evaluations comparing IC and MEM in adult patients have been conducted in Saudi Arabia. There have been several international pharmacoeconomic evaluations done (Attanasio et al., 2000; Edwards et al., 2006; Badia et al., 1999), but with conflicting results. Using data based on the local perspective therefore had the potential to provide insight into the factors influencing local practice and medicines selection. Government institutions in Saudi Arabia, providing free medical treatment, may adopt similar costing strategies that are unique to this Q-VD(OMe)-OPh region .
At a dose of 500mg q6h (cost=SAR 281.60 per day), IC is an attractive alternative to MEM 1 gram q8h (cost=SAR 453.78 per day), particularly in mild to moderate infections.
The overall ADEs were not significantly different between the groups. It was found, though, that ADEs were under-reported. Although more patients had gastrointestinal ADEs in the MEM group, this was not significantly different when compared to IC. These were mainly antibiotic-associated diarrhoea, resulting in C. difficile culture being taken. One patient on IC experienced a seizure. Concern about this adverse effect has prompted the avoidance of IC among health care workers in our hospital. It must be pointed out that Hoffman et al. found no difference in seizure rates between patients treated with IC and MEM (Hoffman et al., 2009). These authors noted that elderly patients, patients with low body weight, at risk of CNS disease, those with a history of seizure and those with renal dysfunction appear to be at increased risk of drug-related seizures. On this basis, the patient in our cohort who developed seizures was at increased risk. This study excluded patients with bacterial meningitis, due to this population being at risk for seizures. In addition, our hospital guidelines (MNGHA, 2012) do not advocate the use of IC in those at increased risk of seizures and in patients with poor renal function. Our study, in agreement with Hoffman et al. Hoffman et al. (2009) did not show significant differences in ADEs associated with IC or MEM.
Total hospital days, especially the total CCU days, in the IC group were significantly higher. The longer CCU days were believed to influence costing, especially in the IC group. Patients varied significantly in regard to the number of CCU days. Independent sample t-tests showed no significant difference in terms of mean daily hospital costs and step-down costs. However the GW costs in the IC group was significantly lower in the IC group compared to MEM (p=0.016). Although total CCU costs were higher, cost per day was not statistically different between the two groups, except in terms of the GW days. More patients in the MEM group spent a greater number of days in the GW unit, which drove up mean costs in this group.
The mean total daily costs of vials in the IC group were much lower than in the MEM group (SAR 250.63 vs. 393.48). This was expected, as the cost of IC, given 4 times daily, would result in daily costs of SAR 281.60 versus MEM, given 3 times daily, at SAR 453.78. The mean costs in our study were mean costs reflecting dose changes as well. In the institution, a previous unpublished study showed that this difference in acquisition costs could result in a savings of more than SAR 2 million riyals per year, if IC was used instead of MEM. This makes IC an attractive choice as a carbapenem in patients with moderate to severe infections. Despite significant differences in acquisition costs, laboratory culture costs, pharmacist and pharmacy aide costs, the total average costs per day was not significantly different between the 2 groups (SAR 4784.46 IC and SAR 4390.13 MEM, p=0.370).