Patients managed with onabotulinumtoxinA (Botox) for their chronic migraine can experience a wear-off in effect before the next scheduled treatment, an international study has found.

The retrospective chart review of 112 patients from treatment centres in six countries including Australia found overall headache days significantly increased in weeks 12 and 13 after injection compared to weeks 5-8 which were considered to represent maximal effect.

Similarly, moderate to severe headache days also increased by week 13 and days with use of acute headache medication also increased in weeks 12 and 13.

Half (51%) of the group experienced a ≥30% wear-off of response to treatment in weeks 12/13 but 25% of the group experienced an early wear-off in effect by weeks 10/11.

The study found factors such as gender, age, headache duration, headache days per month before OnabotA treatment, OnabotA dose or cycle number, the treating headache centre, or concomitant use of oral migraine prophylaxis did not appear to influence wear-off.

“The present data demonstrate that, at least within the first 4 treatment cycles, 13 weeks intervals are not sufficient to maintain a continuing response to OnabotA treatment in many patients, and that an important number of patients show wear‐off even earlier, starting at 10 weeks,” the researchers wrote in Headache.

“This wear‐off phenomenon may negatively affect quality of life of chronic migraine patients under OnabotA treatment,” the study authors concluded.

They noted that the findings were consistent with those of a number of other studies and further research was needed to find strategies to counteract OnabotA wear‐off during a treatment cycle.

Australian investigator on the study Dr Catherine Stark from the Austin Hospital told the limbic the findings confirmed clinical observations that a reasonable proportion of patients do start to experience wear-off around week 11.

“The original trials all looked at a 12-week interval in between dosing but a lot of the headache centres internationally will do three-monthly injections which ends up being about 13 weeks.”

“Certainly in the patients who are getting 13 or more weeks between treatments, there is a much higher chance that they are going to start wearing off towards the end.”

“In Australia our PBS guidelines are that it can be given no more frequently than every 12 weeks because that’s what was in the original trials. It would be great if we were able to give the Botox a little more frequently – so at the 10 or 11 week mark if patients are wearing off – but in our Australian system we can’t do that.”

She said there were quite a lot of patients who will just pay for an extra vial of Botox to cover the gap.

“It’s not subsidised so it’s a really expensive treatment for them …but from a cost point of view there are some patients who will go to a local cosmetic practitioner and just get a few injections in their forehead where they think it is likely to help.”

Dr Stark said while the study didn’t find any less wear-off in the higher dose groups, there was evidence from the cervical dystonia literature that increasing the dose leads to a longer duration of effect.

She said other options for patients were to have another oral prophylactic going in the background which could be boosted to cover the gap or the use of regular anti inflammatories around the time they are going to be wearing off.

Other patients typically settle for managing their lives around the week or two when they know they experience treatment effect wear-off, she said.