Sitagliptin with metformin tablets (Janumet) in fixed-dose combinations of 50/500 mg, 50/850 mg and 50/1000 mg are available on the Pharmaceutical Benefits Scheme (PBS) as of 1 August 2009. The authority required (streamlined) listing is for the treatment of type 2 diabetes when:
- HbA1c is > 7% despite use of metformin, and when a combination of metformin and a sulfonylurea is contraindicated or not tolerated, or
- people are stabilised on a PBS-subsidised regimen of oral medicines for diabetes that includes metformin and sitaglitpin.
The fixed-dose combination tablets are not approved by the Therapeutic Goods Administration or subsidised on the PBS for use as initial drug therapy, or in combination with a sulfonylurea or a thiazolidinedione (glitazone) as part of triple oral therapy.
The authority-required listing for sitagliptin (Januvia) has been revised and is now streamlined to be consistent with the listing for Janumet.1
Starting or switching to the fixed-dose combination tablets
Sitagliptin with metformin fixed-dose combination tablets should be taken twice daily with meals.2 If necessary, increase the dose gradually so as to minimise gastrointestinal side effects with metformin.2
Individualise the starting or switching dose according to the patient's current regimen, level of glycaemic control and tolerability, while maintaining a daily dose of sitagliptin of 100 mg/day.2
The initial dose for patients who are inadequately controlled on metformin is sitagliptin 50 mg twice daily plus the previous dose of metformin.2
For patients who are already taking sitagliptin and metformin, a fixed-dose combination tablet may be prescribed at the dose of each medicine that was used separately.2
Advise patients who are switching to the combination tablets to return their separate medicines to a pharmacy for disposal.
Consider prescribing metformin and sitagliptin as separate medicines for some patients
Sitagliptin with metformin fixed-dose combination tablets provide metformin at a total daily dose of 1000 mg, 1700 mg or 2000 mg. However, some patients may be taking other doses of metformin, such as 1500 mg or 3000 mg daily.
For patients who are less flexible to changes in their current metformin regimen — for example, because of tolerability — it may be preferable to start or continue with sitagliptin and metformin as separate medicines. In doing so, side effects with either drug can also be identified and assessed more easily.
For more information on starting dual oral therapy with sitagliptin, see the NPS RADAR review on Dipeptidyl peptidase-4 inhibitors ('gliptins') for type 2 diabetes mellitus.
- Australian Government Department of Health and Ageing. March 2009 PBAC Outcomes \u2013 Positive Recommendations. http://www.health.gov.au/internet/main/publishing.nsf/Content/EE62734C748A1C12CA25759E0014357F/$File/PBACOutcomesMarch2009-Positiverecommendations.pdf (accessed 25 May 2009).
- Merck Sharp & Dohme (Aust.) Pty Ltd. Janumet product information. 20 April 2009.