Onabotulinum Toxin A for Migraine
Onabotulinum Toxin A (Botox) for Migraine: Botox is now used as a preventative treatment for chronic migraine sufferers. Chronic migraine is defined as headaches on at least fifteen days per month (of which at least eight days are with migraine).
How does it work?
BOTOX blocks the release of neuro-transmitters that are linked to causing pain. Neuro-transmitters are chemicals that carry nerve impulses. To prevent headache, Botox blocks these signals from reaching the central nervous system and causing the nerves to become highly sensitive. Botox is given by injection; divided across seven specific head/neck muscle areas. The number of injection sites start at 31, up to a maximum of 39. Half the injection sites should be on the left side of the head and half on the right. If there is a predominant pain location, further injections may be given (up to the maximum dosage).
The injections should be given by trained personnel in hospital or specialist centres. Always make sure that you see a doctor who is trained in administering botox for migraine, and not for cosmetic reasons. Training is now beginning across Ireland.
The recommended re-treatment schedule is every twelve weeks.
No efficacy has been shown for BOTOX in preventing headaches in patients with episodic migraine (headaches on less than fifteen days per month).
Safety and Side-Effects
In clinical trials for chronic migraine, 26% reported side-effects after the first treatment and this declined to 11% with a second treatment. 9% reported a worsening of headache.
In general, adverse reactions occur within the first few days following injection and are not permanent or long-lasting.
Serious and/or immediate hypersensitivity reactions have been rarely reported. However, these can include anaphylaxis (severe allergic reaction), serum sickness, urticaria (hives), soft tissue oedema (fluid retention) and dyspnoea (breathlessness).
Side effects related to spread of toxin distant from the site of administration have been reported, sometimes resulting in death, which in some cases was associated with dysphagia (difficulty swallowing), pneumonia and/or significant weakness. Patients treated with therapeutic doses may experience exaggerated muscle weakness.
As with any injection, injury can occur. An injection could result in localised infection, pain, inflammation, tenderness, swelling, bleeding, bruising, etc. BOTOX may cause asthenia (lack of strength), muscle weakness, somnolence (drowsiness), dizziness and visual disturbance, which could affect driving and the operation of machinery. If there is a reaction, further injections of BOTOX should be discontinued. Patients or caregivers should be advised to seek immediate medical care if swallowing, speech or respiratory disorders arise.
The safety and effectiveness of BOTOX in the treatment of chronic migraine has not been demonstrated in children (however, chronic migraine is rare in children).
BOTOX is contraindicated:
• In the presence of infection at the proposed injection site(s)
• In individuals with a known hypersensitivity to botulinum toxin type A or to any of the other ingredients used to form ‘Botox’
It is not advised:
• During pregnancy, unless clearly necessary
• During lactation as there is no information on whether BOTOX is excreted in human milk
Patients with underlying neurological disorders including swallowing difficulties are at increased risk of side effects. In this case, treatment should only be used if the benefit of treatment is considered to outweigh the risk.
Patients with neuromuscular disorders may be at an increased risk of more severe effects including acute dysphagia and respiratory compromise from typical doses of BOTOX. Patients with a history of dysphagia (difficulty swallowing) and aspiration (inhaling foreign bodies, such as stomach contents, into the airways) should be treated with extreme caution.
Caution should be used when BOTOX is used in the presence of inflammation at the proposed injection site(s) or when excessive weakness is present in the target muscle. Caution should also be exercised when BOTOX is used for treatment of patients with peripheral motor neuropathic diseases.
In the absence of studies, this medicinal product should not be mixed with other medicinal products.
Two clinical trials involving 1,384 adults were carried out over 60 weeks (five injection cycles).
Patients were eligible for the study if they had a history of migraine and experienced fifteen or more headache days of which at least 50% were migraine or probable migraine during a 28 day ‘baseline’ period.
Two thirds of the patients had previously been treated with at least one other headache prophylactic medication and nearly two thirds of the patients were overusing acute medications.
Patients were divided into two groups – Botox and Placebo.
At baseline, patients in the BOTOX treatment group had an average of 19.1 days with migraine. Patients in the placebo treated group had an average of 18.9 days with migraine. By week 24 BOTOX treated patients averaged 8.2 fewer migraine days. Placebo had 6.2 fewer.
47.1% of BOTOX treated patients (compared to 35.1% of placebo treated patients) achieved >50% reduction in the number of headache days at week 24. After week 56, nearly 70% of BOTOX treated patients experienced ≥50% reduction in migraine days.
Patients treated with BOTOX reported more significant improvements in their quality of life scores and a greater lessening of headache related disability compared with those on placebo.
Most adverse events reported in the trials were mild to moderate and resolved without further problems. The treatment was generally well tolerated and only 3.8% of the BOTOX group stopped treatment.