Write the next sentence in the following story.

How to cope with a spinal headache
Consume caffeine to constrict the blood vessels in your head.
Caffeine is a central nervous system stimulant and causes constriction of the blood vessels within your head.
Since headache is often caused by the dilatation of blood vessels, caffeine helps constrict them and counteract this effect.
Caffeine can be taken both orally and intravenously. A recommended dose of caffeine is 500 mg once or twice daily.