The listing of biologics on the PBS for IBD has not stopped the growth in use of 5-aminosalicylic acid compounds such as mesalazine, a Queensland study shows.
Government expenditure on 5-aminosalicylic acid compounds increased by 173% from $33 million to $90.5 million between 2004 and 2015, an analysis of PBS figures shows.
The dispensed amount of 5-aminosalicylic acid compounds increased by 68% over the same period, when biologic agents such as adalimumab and infliximab for IBD becoming available in the PBS after 2007.
The authors of the analysis said the continued increase in use of 5-aminosalicylic acid compounds may reflect a true increase in rates of IBD, but also due to PBS criteria requiring patients to use these drugs first before being eligible for subsidised biologic treatment.
“Most patients with ulcerative colitis will commence on a 5-aminosalicylic acid compound, and the vast majority likely remain on this agent even if other medications are commenced,” they noted.
Most of the increase in dispensing of 5-aminosalicylic acid compounds was due to wider use of mesalazine, although there was no reason why sulfasalazine should not be used, they said.
“There may … be a perception that sulfasalazine is the inferior drug and a preference among prescribers may exist to either go directly to mesalazine, or to have a very low threshold for the switch. More education may be required among prescribers that sulfasalazine is not inferior if it is tolerated.
They said a genuine trial of sulfasalazine before changing to mesalazine should be strongly encouraged, and clinicians should consider using enteric coated formulations in those with dyspeptic symptoms.
Published in Digestive and Liver Disease, their analysis also showed that the listing of biologics for IBD on the PBS had resulted in a rapid rise in costs. Annual expenditure rose from about $1 million in 2008 to $163 million in 2015, with the most popular agents being adalimumab ($87 million), infliximab ($75 million) and vedolizumab ($2 million).
The higher use of adalimumab may reflect the convenience of its fortnightly subcutaneous injection dosing over the two-monthly intravenous infusions with infliximab, the study authors said.
The PBS listing of availability of biosimilars for IBD such as Inflectra may help contain the rising costs of treatment, especially as the patent for adlimumab expires in 2018, they suggested.
“The earlier and more widespread use of biologic agents may well produce cost savings in other areas of patient care, which should also be taken into consideration when assessing the cost of IBD treatment,” added the authors, which included Dr Neal Martin of the Department of Gastroenterology and Hepatology at Princess Alexandra Hospital, Brisbane,