A 36-year old man presents to the neurologist because for the past 2 years the patient has been experiencing excruciatingly painful headaches around his right eye socket that last approximately 30 minutes. He reports that the headaches tend to occur daily for several weeks and are followed by a period of remission. When he gets these headaches, the patient notes that his right eye starts tearing up and that he gets a runny nose.
Which of the following is the mechanism of action of the most common medication used for relief of this type of headache when it occurs?
- A) 5HT1A/1B agonist
- B) 5HT1A antagonist
- C) 5HT3 antagonist
- D) D2 agonist
- E) GABAA agonist
A) 5HT1A/1B agonist
The patient is describing cluster headaches which are characterized by attacks of severe unilateral pain accompanied by ipsilateral cranial autonomic symptoms and/or restlessness or agitation. Cluster headaches are typically sharp or stabbing in quality and are typicalyl of short duration (15 min up to 3 hours). They commonly occur in the periorbital or temporal regions and are associated lacrimation and rhinorrhea. Abortive treatments (treatments given to the patient while the headache is occurring or about to occur) include oxygen and triptans (particularly sumatriptan and zolmitriptan). Sumitriptan is a 5HT1A/1B agonist. Alternative treatments include intranasal lidocaine, oral ergotamine, and octreotide.
Answer choice B: 5HT1A antagonists are a diverse class of medications that include antipsychotics and antidepressants as well as other uses.
Answer choice C: 5HT3 antagonists are antiemetics used in the treatment of nausea and vomiting with the exception of alosetron and cilansetron, which are used in the treatment of irritable bowel syndrome.
Answer choice D: D2 agonists are used in Parkinson’s disease and to a lesser extent in the treatment of depression, hyperprolactinemia, and restless legs syndrome.
Answer choice E: GABAA agonists typically produce sedative effects and may also cause other effects such as anxiolytic, anticonvulsant, and muscle relaxant effects.
Key Learning Point
Acute therapy for cluster headache includes oxygen and triptans which are 5HT1A/1B agonists.