BackgroundBotulinum toxins are considered first-line therapy for treatment of cervical dystonia (CD) and must be injected on a repeat basis. Understanding the duration of clinical benefit of botulinum toxins and its impact on health care utilization are thus important in the contemporary environment. However, there is currently no overall consensus on the duration of effect of onabotulinumtoxinA in the treatment of CD. We performed a systematic review and meta-analysis to identify the duration of effect of onabotulinumtoxinA in CD and investigate factors that may influence it.MethodsA systematic literature search identified prospective or retrospective studies reporting duration of effect of onabotulinumtoxinA for the treatment of CD. Inclusion criteria included peer-reviewed, non-review, English-language articles published between January 1980 and January 2013. A formal meta-analysis using Comprehensive Meta-Analysis Version 2 was conducted to identify the duration of effect of onabotulinumtoxinA in the treatment of CD; both fixed and random effects models were performed. Subgroup analyses were performed to identify factors that influenced the duration of effect of onabotulinumtoxinA.ResultsA total of 18 studies (including >1,900 patients) met the inclusion criteria and were used for the meta-analysis. The mean duration of effect of onabotulinumtoxinA in CD was found to be 93.2 days (95% CI 91.8-94.6 days) for the fixed effects model and 95.2 days (95% CI 88.9-101.4 days) for the random effects model. A meta-regression found that dose of onabotulinumtoxinA and country of origin influenced the duration of effect of onabotulinumtoxinA, whereas quality score of the article and study type did not. In particular, doses ≥180 Units were associated with longer durations of effect than doses <180 Units (107-109 days vs. 86-88 days, respectively; p < 0.01). Limitations included pooling studies that used discrete definitions of duration and had different designs and study quality.ConclusionsBased on the published literature, the mean duration of effect of onabotulinumtoxinA in CD was 93-95 days (13.2-13.5 weeks). This suggests that, in general, patients with CD treated with onabotulinumtoxinA should require ~4 treatments per year.

CONCLUSIONS: GA was found to reduce relapses and clinical progression compared with placebo, and clinical progression in comparison with interferons. Serious adverse events were comparable with interferons. Qualitative and quantitative methods demonstrated that the benefits of GA outweigh the risks but the results differ substantially depending on the quantitative risk-benefit model used. OBJECTIVES:Cervical dystonia is a disabling, painful condition involving involuntary movement and posturing of the head and neck. Botulinum toxin injections are the standard of care in the symptomatic management of this condition, but need to be re-administered regularly to maintain a stable improvement. The duration of clinical effect and thus, frequency of need for reinjection may be dependent on the product used and can impact annualized drug and health care utilization costs. METHODS: A literature search was undertaken to identify prospective or retrospective studies reporting duration of effect of onabotulinumtoxinA (BOTOX®). A formal meta-analysis was conducted using Comprehensive Meta-Analysis Version 2. Both a fixed effects and random effects model were performed. The quality of each identified journal article was evaluated using the Cho & Bero Quality scoring instrument by two separate investigators. Differences in scores were resolved through conference. Subgroup analyses were performed on several moderating variables including study quality and dose of onabotulinumtoxinA. RESULTS: Of the identified potential journal articles, 13 studies met the inclusion criteria and were used for the meta-analysis. The duration of effect of onabotulinumtoxinA in cervical dystonia was found to be 13.7 weeks (95% CI 13.4 -13.9 weeks) for the fixed effects model and 13.5 weeks (95% CI 12.7 -14.3 weeks) for the random effects model. A meta-regression found that the higher the quality score, the shorter the duration of effect. Another meta-regression found that doses of onabotulinum-toxinA greater than 200U generally resulted in a longer duration of effect than doses below 200U. CONCLUSIONS: Based on the published literature, the duration of effect of onabotulinumtoxinA was 13-14 weeks. This suggests that, in general, patients with cervical dystonia treated with onabotulinumtoxinA should require approximately 4 treatments per year. A dose-effect for duration was also identified.