Patient-centred evaluation of a reduced dose of botulinum toxin A in the management of myofascial pain

In our previous service evaluation, we reported improvement in patients’ pain scores for masseteric pain and spasm, following injection of 50 units of botulinum toxin A (BtA), measured using visual analogue scales (VAS). We have recently introduced a lower dose BtA protocol, for appropriately selected patients, aimed to evaluate whether this is also effective at relieving symptoms of masseteric pain and spasm. The rationale was to reduce side-effects and costs.

VAS scores were measured before and after treatment for 48 patients who received treatment with the original BtA protocol (“Protocol A” - the historical cohort who received 50 units) and for 46 patients who receieved a modified BtA protocol (“Protocol B” - the current cohort who received 25 units).

Patients in both treatment groups reported severe symptoms prior to treatment. Patients who received protocol B reported, on average, a 5 unit improvement in VAS following treatment (95 % confidence interval 4.3 to 5.7 improvement in VAS). There was no evidence that protocol B was less effective, despite the lower dose.

We recommend a reduced dose of BtA, of 25 units, for injection for appropriately selected patients with masseteric pain and spasm. A lower dose of BtA reduces wastage, particularly for single muscles injection and may reduce the incidence of unwanted side-effects. Reducing the standard dose of BtA will reduce costs for healthcare providers and may therefore facilitate funding for provision of intramuscular injection of BtA, where justified.