Comparative study on the combined effects of bunazosin and nipradilol or timolol on intraocular pressure in normotensive rabbits.
OBJECTIVE
To compare the ocular hypotensive effect of nipradilol and timolol in combination with bunazosin in rabbits.


METHODS
The intraocular pressure (IOP) in normal rabbits was measured using an applanation pneumatonograph. Nipradilol, timolol, and bunazosin were instilled, individually or in combination, into the inferior conjunctival sac.


RESULTS
Nipradilol (0.25%), timolol (0.5%), and bunazosin (0.01%) individually lowered IOP. The IOP-lowering effects of both nipradilol and timolol were significantly enhanced by the combined application of bunazosin (0.01%). In the presence of 5% timolol or 0.1% bunazosin, IOP was further lowered by the addition of nipradilol. The IOP-lowering effect of nipradilol was partly inhibited by pretreatment with c-PTIO (10 mM), a nitric oxide (NO)-trapping agent.


CONCLUSIONS
The present study demonstrated that the IOP-lowering effects of nipradilol are due to beta- and alpha1-blocking and NO-donating actions, and bunazosin has an additive effect on the IOP-lowering effect of nipradilol or timolol.
Orihashi
Masahiro
M
Department of Clinical Pharmacology, Graduate School of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Toyama, Japan.
Shima
Yuichiro
Y
Teika Pharmaceutical Company, Toyama, Japan.
Tsuneki
Hiroshi
H
Department of Clinical Pharmacology, Graduate School of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Toyama, Japan. htsuneki@ms.toyama-mpu.ac.jp.
Kimura
Ikuko
I
Department of Clinical Pharmacology, Graduate School of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Toyama, Japan.
D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage*; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D005500:Follow-Up Studies; D007429:Intraocular Pressure / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009883:Ophthalmic Solutions; D011412:Propanolamines / Q000008:administration & dosage*; D011799:Quinazolines / Q000008:administration & dosage*; D011817:Rabbits; D013999:Timolol / Q000008:administration & dosage*
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D009883:Ophthalmic Solutions; D011412:Propanolamines; D011799:Quinazolines; D013999:Timolol; C018176:bunazosin; C036089:nipradilol