Background In February 2008, in order to reduce the number of clostridium difficile infections, we changed the antibiotic guidelines at our trust.

The aim of the change was to restrict the use of amoxicillin/clavulanic acid, cephalosporins and quinolones In their place we promoted the use of co-trimoxazole This change led to a dramatic reduction in cases of clostridium difficile infection Unfortunately since 2008 there have been a number of problems with the supply of IV co-trimoxazole In particular there was a period of six months in June–December 2011 where IV co-trimoxazole was completely unavailable.;

Purpose To examine the effects of the supply problem on use of IV co-trimoxazole and alternative agents.

Materials and methods Antibiotic use was calculated from the pharmacy computer system and converted into DDDs using the WHO-defined ATC code system. Three time periods were compared: period 1 pre-supply problems (January to June 2011), period 2 during the supply problems (July to December 2011) and period 3 post-supply problems (January to June 2012).

Results Comparing periods 1 and 2: IV co-trimoxazole use fell from 2037 to 518 DDDs (a 75% reduction). Piperacillin/tazobactam increased by 38% from 6375 to 8821 DDDs and meropenem increased by 106% from 2207 to 4561 DDDs. From period 2 to 3: piperacillin/tazobactam use only fell by 6% and meropenem use by 4.5%

Conclusions Guidelines that rely heavily on co-trimoxazole face major disruption when there are supply problems. This led to an increase in use of broad spectrum antibiotics which remained high even when supplies of co-trimoxazole returned to normal.

No conflict of interest.