An economic analysis carried out for NICE finds that addition of a proton-pump inhibitor (PPI) to NSAID or COX-2 inhibitor therapy for people with osteoarthritis is likely to be cost-effective, providing individual cardiovascular and gastrointestinal risks are taken into account when choosing the specific drug.
The authors of this cost utility analysis, which was carried out as part of the update of NICE guidance on the topic, note that NSAID and COX-2 inhibitors are widely used for symptomatic relief of osteoarthritis, and that recent changes in PPI costs and new evidence on adverse effects potentially alter the cost-effectiveness of prescribing gastroprotection to patients on these drugs. This evaluation was intended to determine the cost-effectiveness of these drugs in patients with osteoarthritis, and that of adding gastroprotection.
The model used estimates the net impact of the treatment options on patient outcomes and expenditure, taking account of effects on the incidence of gastrointestinal and cardiovascular adverse events as well as improvements in the control of osteoarthritis symptoms. Data on effectiveness were obtained from a meta-analysis of randomised controlled trials. Adverse effect data were taken from large published randomised controlled trials that reported gastrointestinal and cardiovascular adverse events for diclofenac, naproxen, ibuprofen (which account for most NSAID prescriptions in the UK), celecoxib, and etoricoxib.
Addition of a PPI to each drug was also modelled, as were treatment with paracetamol and no treatment. Costs included those for treating adverse effects, as well as drug costs and GP, outpatient costs etc. The main outcome measure was cost effectiveness, which was based on quality adjusted life years gained. Results were evaluated for two cohorts – one aged 55, and one aged 65 with higher baseline risks of gastrointestinal and cardiovascular risks.
The model found that once the costs of treating adverse effects are taken into account, adding the lowest-cost PPI to NSAID or COX-2 therapy was cost-effective, even for low-risk patients, with a cost per QALY of less than £1,000. Adding a PPI to a COX-2 inhibitor was cast effective by standard measures (about £10,000 per QALY) for all patients, however the degree of uncertainty around this was high. Because of uncertainties around relative adverse event rates, it was difficult to model the relative cost-effectiveness for individual drugs. The superiority of celecoxib over the other drugs was tentative given the debate over cardiovascular event rates in the trial used (CLASS), and the differences between the traditional NSAID used were small.
The authors conclude that it is cost-effective to prescribe a PPI to patients taking an NSAID or COX-2 inhibitor for osteoarthritis, even when they are at a low risk of gastrointestinal adverse events. This is because the evidence base for PPI has increased and their cost has fallen. Because of the high rate of adverse effects with these drugs and doubt over their long-term efficacy, they should be prescribed only as and when required, and at the lowest effective dose. Because the results were very sensitive to adverse event data, drug choice for the individual patient should take into account their own gastrointestinal and cardiovascular risk profile.