Sequential drug decision problems in long-term medical conditions: a case Study of Primary Hypertension Eunju Kim ba, ma, msc

4.3.3Consideration of drug switches

Richter et al’s study was the only study to address the cost-effectiveness of different sequential treatment strategies over 15 months^[257]. A decision tree model was built to explore the effect of adding ARBs (i.e., telmisartan) to the sequential treatment strategies starting with Ds, CCBs, ACEIs, BBs or ARBs. The initial drug was switched to the next drug if a patient failed to control blood pressure every three months. The probability that a specific drug was selected as the second-line therapy was based on physicians’ opinion. The study concluded that adding ARBs could reduce the mean time to control blood pressure and reduce total costs in the short-term.

There were two studies that allowed only one opportunity to switch a drug when a CVD or intolerable AEs occurred. In Stafilas et al’s CMA, which compared the costs of Ds, BBs, CCBs, ACEIs and ARBs, Ds was switched to ACEIs and the other drugs were switched to Ds in the case of AEs or lack of efficacy^[254]. For simplicity, they also assumed that only one drug switch from conventional therapy to ACEIs or vice versa could occur if congestive HF developed, blood pressure was not controlled after the first three months of initiation of drug therapy or in response to AEs or non-response.

The other studies focused on the impact of an initial drug on long-term costs and health outcomes assuming that a patient continues with the drug for a defined time period regardless of the health state transitions. Three studies mentioned that they could not consider drug switching because of limited clinical or economic data of each drug and the complexity of modelling the interactive effects between various health states and drug choice over time^{[42, 246, 258]}. Tran et al also stated that they restricted the CEA of antihypertensive drugs to the comparison of initial drugs because there was no clear evidence of optimal secondary drugs after the initial drug fails^[246]. The NICE HTA report stated that the impact of drug discontinuation and switching between treatments on effectiveness was implicitly considered in intention-to-treat (ITT) trial data^[223].