COMBIGAN EYE DROPS

Mechanism of action of COMBIGAN
The combination of brimonidine and timolol in an ophthalmic solution reduces intraocular pressure (IOP) by reducing aqueous humour production and increasing uveoscleral outflow.
This product contains a combination of brimonidine tartrate and timolol maleate. Each of these components is used to decrease elevated intraocular pressure.
Brimonidine tartrate is a relatively selective alpha adrenergic receptor agonist. Brimonidine tartrate lowers IOP by reducing aqueous humour production and increasing uveoscleral outflow. Timolol maleate is a non-selective beta-adrenergic receptor blocking agent that combines reversibly with the beta-adrenergic receptor. The precise mechanism of action of timolol maleate in lowering intraocular pressure is not yet clearly established, although a fluorescein study and tonography studies indicate that its predominant action may be related to reduced aqueous humour formation.
The peak ocular hypotensive effect occurs at approximately two hours post-dosing for brimonidine tartrate and one to two hours for timolol maleate. The duration of effect is 12 hours or greater for brimonidine tartrate and 24 hours for timolol maleate.
 

I am taking at night Alphagan P and Xalatan and in the morning Combigan.

Alphagan P  peaks 2 hours after dosing losing steadily its effect during the following 2-3 hours.  That's why you can take Alphagan P every 8 hours 3 times a day if this is the only thng you are taking.

Xalatan peak effect is around 2-3 hours after dosing and may last 9+hours

So the post from Anonymous talking about the importance of when to  take the drops really open my eyes (no pun intended)  I was taking Alphagan P and Xalathan around 11 or midnight.  Definitely I need to take these much earlier since  the effect starts kicking 2-3 hours after dosing. 

The ideal would be to take Xalathan first at around 9 PM and then Alphagan P 2 hours later... but according to doctors you need to take Alphagan P first and then Xalathan 5 to 10 minutes later. Well some doctors say 30 minutes later.... Go figure????