47,48 Gabapentin is typically a well-tolerated medication but more common AEs include somnolence and fatigue, dizziness, weight gain, peripheral edema, and ataxia. In a small open-label study of baclofen 10 mg 3 times daily, 6 of 9 subjects went into remission within 1 week and an additional 1 subject had improvement followed by remission at week 2.49 Although adverse events were not reported by subjects in this study, more PI3K inhibitor common AEs to baclofen include drowsiness, dizziness, ataxia, and muscle weakness. Clonidine, given as a 5 mg to

7.5 mg transdermal patch (that delivers the drug at a rate of 0.2-0.3 mg daily for 1 week), has been studied in 2 small open-label studies.50,51 In the first, which included 8 ECH and 5 CCH patients, there were significant reductions in mean attack frequency, pain intensity, and attack duration.50 However, a second study including 16 ECH patients failed to confirm these positive results.51 Tiredness and reduction in blood pressure were AEs noted in these studies. An open-label study of

botulinum toxin type A as add-on therapy in 3 ECH and 9 CCH patients had mixed results.52 Fifty units injected ipsilateral to the headache resulted in headache remission in 1 CCH patient, improvement in attack frequency and severity in an additional 2 CCH patients, improvement in a continuous baseline headache with no change LY294002 ic50 in superimposed cluster attacks in an additional 1 CCH patient, and no

benefit in the remaining 8 patients. More common AEs to botulinum toxin therapy include weakness of injected muscles and pain at injection sites. Corticosteroids are often prescribed concurrent with initiation of maintenance prophylaxis in order to quickly obtain cluster control. Oral and intravenous corticosteroids may both provide benefit. Varying doses of oral prednisone, ranging from 10 mg/day to 80 mg/day, were evaluated in a study of 9 episodic and 10 chronic cluster patients.53 Peak prednisone dose was given for 3 to 10 days and tapered over 10 to 30 days. Complete relief from CH was seen in 11 patients, 3 had 50-99% relief, 3 had 25-50% relief, and 2 patients had no benefit. The ECH and CCH patients had similar responses. Investigators Chloroambucil observed that prednisone doses of 40 mg or higher were needed for benefit. Headache recurrence was common during the prednisone taper. Other studies of oral prednisone have had similar results.54,55 Intravenous corticosteroids, sometimes followed by oral steroids, may also provide benefit for transitional cluster therapy.56,57 A single high dose of intravenous methylprednisolone (30 mg/kg body weight over 3 hours) delivered on the eighth day of an active cluster period provided 10 of 13 treated patients with 2 or more days of attack cessation.56 The mean interval between steroid treatment and attack recurrence was 3.8 days. Three patients had complete cluster remission.