Sumatriptan
Subcutaneous sumatriptan is the most effective medication for the symptomatic relief of cluster headache. In a placebo-controlled study, 6mg of injectable sumatriptan was significantly more effective than placebo, with 74% of patients having complete relief by 15 minutes compared with 26% of placebotreated patients.⁵ In long-term, open-label studies, sumatriptan is effective in 76% to 100% of all attacks within 15 minutes even after repetitive daily use for several months.⁶ Interestingly, sumatriptan appears to be 8% less effective in chronic cluster headache than episodic cluster headache. Sumatriptan is contraindicated in patients with uncontrolled hypertension, past history of myocardial infarction or stroke.As almost all cluster patients have a strong history of cigarette smoking, the physician must closely monitor cardiovascular (CV) risk factors in these patients.

Sumatriptan nasal spray (20mg) has been shown to be more effective than placebo in the acute treatment of cluster attacks. In over 80 patients tested, intranasal sumatriptan reduced cluster headache pain from very severe, severe, or moderate to mild or no pain at 30 minutes in 58% of sumatriptan users, compared with 30% of patients given placebo on the first attack treated, while the rates were 50% (sumatriptan) compared with 33% (placebo) after the second treated attack. ⁷ Sumatriptan nasal spray appears to be efficacious for cluster headache but less effective than subcutaneous injection. Sumatriptan nasal spray should be considered as a cluster headache abortive in patients who cannot tolerate injections or when, situationally (e.g. an office setting), injections would be considered socially unacceptable.

In many instances cluster headache patients may need to use sumatriptan more than once a day for days to weeks at a time. Hering ⁸  noted that the use of daily injectable sumatriptan in four cluster patients led to a marked increase in the frequency of cluster attacks three to four weeks after initiating treatment. In three patients the character of the cluster headache changed while two patients experienced prolongation of their cluster headache period. Withdrawal of sumatriptan reduced the frequency of headaches. Even though daily sumatriptan may be benefiting a cluster headache patient the goal should be to have them cluster free on preventive medication not using abortives to achieve cluster-free status.

Oxygen
Oxygen inhalation is an excellent abortive therapy for cluster headache.Typical dosing is 100% oxygen given via a non-rebreather face mask at seven liters to 10 liters per minute for 20 minutes. Past studies indicate that about 70% of cluster patients respond to oxygen therapy.9 In some patients oxygen is completely effective at aborting an attack if taken when the pain is at maximal intensity, while in others the attack is only delayed for minutes to hours rather than completely alleviated. It is not uncommon for a cluster patient to be headache-free while on oxygen but immediately redevelop pain when the oxygen is removed. Oxygen is overall a very attractive therapy as it is completely safe and can be used multiple times during the day, unlike sumatriptan or ergots, for example, which if used too frequently could cause cardiac ischemia. Large oxygen tanks are prescribed for cluster patients’ homes while portable tanks can be taken to the workplace. There may be a gender discrepancy in response to oxygen. Rozen et al.¹⁰ reported that only 59% of female cluster patients at their academic center responded to oxygen while 87% of men responded to oxygen. A recent study showed that individuals who do not respond to typical oxygen dosing may respond at higher flow rates up to 15 liters per minute.¹¹ A small, open-label study of hyperbaric oxygen (2atm) delivered over 30 minutes demonstrated efficacy in six of seven cluster patients within five to 13 minutes, with these patients reporting complete or partial interruption of the cluster period.¹²

Transitional Therapy
Transitional cluster therapy is a short-term preventive treatment that bridges the time between cluster diagnosis and the time when the true traditional maintenance preventive agent becomes efficacious. Transitional preventives are started at the same time the traditional preventive is begun. The transitional preventive should provide the cluster patient with almost immediate pain relief and allow the patient to be headache-free or near headache-free while the traditional preventive medication dose is being tapered up to an effective level.When the transitional agent is tapered off the maintenance preventive will have kicked in, thus the patient will have no gap in headache preventive coverage (see Table 2).

Corticosteroids
A short course of corticosteroids is the best known transitional therapy for cluster headache. Typically, within 24 to 48 hours of administration, patients become cluster-free and by the time the steroid taper has ended the patients’ main preventive agent has started to become effective. Prednisone or dexamethasone are the most typically used corticosteroids in cluster. A typical taper would be 80mg of prednisone for the first two days followed by 60mg for two days, 40mg for two days, 20mg for two days, 10mg for two days then ceasing to use the agent. There is no set manner in which to dose corticosteroids in cluster headache.