The purpose of this study was to evaluate the drop characteristics of newer
glaucoma medicines compared to timolol solution and timolol gel forming so
lution (Timoptic-XE(TM), Merck).
We evaluated latanoprost 0.005% (2.5 mi bottle), brimonidine 0.2%, apraclon
idine 0.5%, dorzolamide 2%, timolol solution 0.5% (5 and 10 mi bottles), an
d timolol gel forming solution 0.5% (5 mi bottle) in 14 patients with prima
ry open-angle glaucoma or ocular hypertension. Each patient placed 10 drops
onto an analytical scale (one drop every 10 seconds) for all ten preparati
ons. Patients then attempted to instill 10 drops of a tear replacement solu
tion into their ocular cul-de-sac. Medication bottles were weighed before a
nd after patients dispensed from the bottle and then after the bottle was e
mptied. Weights were converted to volume using the density of the medicine.
A statistical difference existed between groups for mean drop volume with l
atanoprost having the smallest drop volume (.0273 +/- .004 mi) (P<0.005). A
ll manufacturers filled correctly or overfilled their bottles with product
and had <10% of medicine wasted. Patients instilled 77.9% of the tear solut
ion correctly. When dosed according to labeling, latanoprost had the lowest
cost of therapy at $0.87 daily compared to the other newly released medica
tions (range $1.05 to $1.40). Latanoprost was more expensive, however, than
timolol maleate solution or gel (range $0.45 to $0.54 per day).
Latanoprost therapy is less expensive per day than dorzolamide, brimonidine
or apraclonidine, but more expensive than timolol maleate. Cost per day co
uld be further reduced by limiting medicine wastage upon instillation, howe
ver.