Aside from the fact that aqueous production decreases at night (and Timolol decreases aqueous formation) what are other reasons why Timolol is less effective at night?
A number of studies indicate that the rate of aqueous flow during sleep is much lower than during waking hours, and that drugs affecting aqueous flow can have different effects at different times of day. Timolol, which has a substantial effect when tested during the day, has been found to have no measurable effect at night. This has been attributed to the existence of a baseline rate of flow that cannot be further suppressed by any drug, or to the absence of timolol-blocking activity in the sleeping eye.The magnitude of the normal decrease in aqueous humor production that occurs naturally each night was twice as much as that achieved by timolol during the daytime. This explains why nocturnal reduction in aqueous flow beyond the normal decrease at night could not be achieved and why nocturnal IOP was not affected by timolol.
Check this link too
http://archopht.jamanetwork.com/article.aspx?articleid=1149523
Timolol, in the concentrations of 0.25% and 0.50%, is an antiglaucoma medication that helps reduce aqueous secretion by 20-50%, thereby reducing the IOP by 20-30%.
And during the night hours, the parasympathetic nervous system activity is increased, and the secretion seems to be increased consequentially. This secretion increase brings about a concurrent increase in the IOP. This increased IOP cannot be countered by timolol as the secretion is way rapid as compared to the day hours.
If increasing the intake (food), the pressure decreases as the diabetic disease
Duration of action of B-blockers including Timolol is 12 hours and also taken into account that IOP spikes take a place early in the morning Timolol is prescribed twice a day - at 8 or 9 ap and 8 or 9 pm respectively
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