Comparison of dorzolamide and timolol as suppressors of aqueous humor flow in humans.
OBJECTIVE
To measure the effectiveness of topical 2% dorzolamide hydrochloride (Trusopt, Merck & Co Inc, Whitehouse Station, NJ) as a suppressor of aqueous humor flow in the human eye as compared with the effectiveness of 0.5% timolol maleate (Timoptic, Merck & Co Inc) and to measure the additivity of the 2 drugs.


METHODS
A randomized, double-masked, placebo-controlled study of 40 human subjects was carried out in 2 academic centers (Mayo Clinic, Rochester, Minn, and University of Uppsala, Uppsala, Sweden). The rate of aqueous flow was measured from 8 AM to 4 PM by means of fluorophotometry after administration of doses of each drug singly and both drugs together.


RESULTS
Dorzolamide reduced aqueous flow from 3.07 +/- 0.63 microL/min (mean +/- SD) to 2.53 +/- 0.60 microL/min, a reduction of 18% (P < .001). Timolol reduced aqueous flow from the same beginning rate to 1.64 +/- 0.35 microL/min, a reduction of 47% (P < .001). The inhibitory effect of timolol was 2.6 times the inhibitory effect of dorzolamide (P < .001). The 2 drugs were almost completely additive, and together reduced the flow to 1.37 +/- 0.33 microL/min, a reduction of 55%. Consistent effects were observed on intraocular pressure.


CONCLUSIONS
Timolol is more effective than dorzolamide as a suppressor of aqueous humor flow in the normal human eye. Timolol and dorzolamide are additive in their effects, both on aqueous flow and intraocular pressure.
Wayman
L
L
Mayo Medical School, Rochester, Minn., USA.
Larsson
L I
LI
Maus
T
T
Alm
A
A
Brubaker
R
R
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage*; D000328:Adult; D001082:Aqueous Humor / Q000187:drug effects* / Q000378:metabolism; D002257:Carbonic Anhydrase Inhibitors / Q000008:administration & dosage*; D004311:Double-Blind Method; D004338:Drug Combinations; D004357:Drug Synergism; D005260:Female; D015590:Fluorophotometry; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D009883:Ophthalmic Solutions; D013449:Sulfonamides / Q000008:administration & dosage*; D013876:Thiophenes / Q000008:administration & dosage*; D013999:Timolol / Q000008:administration & dosage*
D000319:Adrenergic beta-Antagonists; D002257:Carbonic Anhydrase Inhibitors; D004338:Drug Combinations; D009883:Ophthalmic Solutions; D013449:Sulfonamides; D013876:Thiophenes; D013999:Timolol; C062765:dorzolamide