Ergotamine works by stimulating receptors called serotonin (or 5HT) receptors that are found in the brain. A natural substance called serotonin normally acts on these receptors, causing blood vessels in the brain to narrow. Ergotamine mimics this action of serotonin by directly stimulating the serotonin receptors in the brain. This narrows the blood vessels and so relieves the pain of migraine headaches.
Ergotamine also acts on other types of receptors found on the walls of blood vessels, called alpha receptors. This also causes the blood vessels to narrow.
Cyclizine is an anti-nausea medicine which acts on the vomiting center of the brain, which is responsible for causing nausea and the vomiting reflex. Cyclizine stops this area of the brain from receiving the messages that make it cause these reactions. It is included in this medicine to treat the nausea and vomiting associated with migraine.
Caffeine is also included in this medicine to help enhance the effect of ergotamine.