OBJECTIVES: There are two forms of injectable IV diclofenac available (Dyloject bolus and Voltarol infusion). We conducted a cost minimization analysis to determine the total cost of each treatment strategy. METHODS: A decision-analytic model was developed to estimate total treatment costs of IV bolus versus IV infusion diclofenac. The modeled population was patients who post-operatively would require injectable NSAIDs to control their pain. The model timeframe was for the duration that a patient required post-operative pain management with injectable medication. The model inputs included the actual/estimated cost of medicines, the cost of the IV administration process (staff time and consumables), and the cost of treating adverse events (staff time, medicines and consumables). The unit costs and resources are based on UK data. The results are expressed as Pounds Sterling and as average cost per patient. One-way sensitivity analyses were also conducted on key parameters. RESULTS: The total cost of treating post-operative pain was less with IV bolus diclofenac (Dyloject) than with IV infusion diclofenac (Voltarol). Diclofenac IV bolus cost a mean £27.84 per patient overall versus diclofenac IV infusion mean cost of £78.61 per patient. The difference in overall cost is attributable to the cost of NSAIDs (IV bolus £12.19 versus £1.69 IV Infusion), the cost of administering the NSAID (IV bolus £9.72 versus £49.73 IV Infusion) and the cost of consumables (IV bolus £1.40 versus £16.72 IV infusion). The difference in the costs of rescue medication (IV bolus £2.48 versus £6.14 IV infusion) and of treating adverse events (IV bolus £2.061 versus £4.33 IV infusion) was less. One-way sensitivity analyses show the results are sensitive to the cost of staff time and consumables. CONCLUSION: Diclofenac IV bolus (Dyloject) is cost saving relative to diclofenac IV infusion (Voltarol) in the treatment of post-operative pain.