Effects of topical 0.5% levobunolol alone or in association with 2% dorzolamide compared with a fixed combination of 0.5% timolol and 2% dorzolamide on intraocular pressure and heart rate in dogs without glaucoma

The goal of glaucoma management is to reduce intraocular pressure (IOP) and maintain it at a level compatible with the health of the optic nerve. New therapies are constantly being sought. Topical instillation of levobunolol 0.5%, alone or with dorzolamide 2%, has a hypotensive effect on the IOP in healthy dogs, and levobunolol combined with dorzolamide produces a stronger hypotensive effect than the combination of timolol and dorzolamide. All animals tolerate these topical medications well with no signs of discomfort, and no ocular side effects have been observed. Levobunolol, alone or in combination with dorzolamide, induces bradycardia, as does timolol with dorzolamide.

Vasodilatory mechanism of levobunolol on vascular smooth muscle cells

Topical application of levobunolol hydrochloride, a beta-adrenergic antagonist used for treatment of glaucoma, is reported to increase ocular blood flow. We studied the mechanism of levobunolol-induced vasodilation in arterial smooth muscle. The effects of levobunolol or other agents on isolated, pre-contracted rabbit ciliary artery were investigated using an isometric tension recording method. The effects of the same agents on intracellular free calcium ([Ca(2+)](i)) in cultured human aortic smooth muscle cells were also studied by fluorophotometry. Levobunolol relaxed ciliary artery rings that were pre-contracted with either high-K solution, 1microM histamine, 10microM phenylephrine, or 100nM endothelin-1. The relaxation induced by levobunolol was concentration-dependent over the range of 10microM to 0.3mM. Inhibition of endothelial nitric oxide synthase or denudation of the endothelium did not affect this relaxation. Histamine-induced contractions were inhibited by the histamine H(1) antagonist pyrilamine. Radioligand binding experiments showed that levobunolol did not bind to the H(1) receptor. Further, histamine induced transient contraction in Ca(2+)-free solution, and levobunolol inhibited this contraction by 74.6+/-11.0%. In cultured smooth muscle cells in the presence of extracellular Ca(2+), levobunolol significantly inhibited the histamine-induced elevation of [Ca(2+)](i). However, it did not inhibit the increase of [Ca(2+)](i) in histamine-stimulated cells incubated in Ca(2+)-free solution. These results indicate that levobunolol may relax rabbit ciliary artery by two different mechanisms. First, the relaxation could be due to the blockade of Ca(2+) entry through non-voltage-dependent Ca(2+) channels. Second, levobunolol may change the Ca(2+) sensitivity of vascular smooth muscle cells.

Effects of antiglaucoma drugs on calcium mobility in cultured corneal endothelial cells

The aim of this study was to estimate the effects of various antiglaucoma drugs including betaxolol, timolol, levobunolol, brimonidine, carteolol, dipivefrin, dorzolamide, brinzolamide, latanoprost, unoprostone, and pilocarpine on intracellular free Ca2+ ([Ca2+]i) mobility in cultured bovine corneal endothelial cells. Various antiglaucoma drugs were diluted from original concentrations to 1/ 100, 1/ 1,000, and 1/ 10,000. The [Ca2+] mobility was studied by spectrofluorophotometry after loading with the ester of fura-2 (fura-2/AM). It was found that timolol (58 microM and 5.8 microM), levobunolol (171 microM, 17.1 microM, and 1.71 microM), betaxolol (162 microM, 16.2 microM, and 1.62 microM), carteolol (680 microM and 68 microM), dipivefrin (28 microM and 2.8 microM), dorzolamide (616 microM and 61.6 microM), brinzolamide (260 microM), latanoprost (1.1 microM), unoprostone (28.2 microM, 2.82 microM, and 0.282 microM), and pilocarpine (408 micro and 40.8 microM) induced a significant increase in [Ca2+]i. Nevertheless, only brimonidine (68 microM and 6.8 microM) decreased [Ca2+]i concentration significantly. Benzalkonium chloride preservative did not affect [Ca2+]i after addition of 0.001, 0.0001 and 0.00001 mg/mL to cells. These results indicate that all antiglaucoma drugs may affect the physiologic function of corneal endothelial cells through change of [Ca2+]i mobility.

Binding affinities of ocular hypotensive beta-blockers levobetaxolol, levobunolol, and timolol at endogenous guinea pig beta-adrenoceptors

The current study determined the relative affinities and selectivities of numerous beta-adrenoceptor antagonists at the endogenous beta(1)- and beta(2)-adrenoceptors in guinea pig heart and lung, respectively, using [(3)H]-CGP12177. Specific binding of [(3)H]-CGP12177 comprised 80 +/- 0.2% (n = 11) and 94 +/- 0.2% (n = 16) of the total binding in washed heart and lung homogenates, respectively. Concentration-dependent displacement of [(3)H]-CGP12177 binding from beta-adrenoceptors in both preparations was observed with nine different beta-adrenoceptor antagonists. Levobetaxolol, betaxolol, CGP-20712A, levobunolol, and timolol yielded bi-phasic (two-site-fit) competition curves in the heart, while CGP-20712A, ICI-118551 and levobunolol produced bi-phasic curves in the lung preparation. The high-affinity component of [(3)H]-CGP12177 binding in the heart and lung reflected binding to beta(1)-receptors and beta(2)-receptors, respectively. The binding inhibition parameters (IC(50)s) for displacement of [(3)H]-CGP12177 from these predominantly high-affinity sites were: levobetaxolol (24.9 +/- 1.6 nM heart, 4810 +/- 367 nM lung), racemic betaxolol (37.9 +/- 8.7 mM heart; 8840 +/- 424 mM lung), CGP-20712A (4.6 +/- 0.9 nM heart; 171,000 +/- 109,000 nM lung), ICI-118551 (9230 +/- 3240 nM heart; 2.9 +/- 0.6 nM lung), levobunolol (42 +/- 15 nM heart, 0.3 +/- 0.2 nM lung), (l)-timolol (3.1 nM heart, 2.9 +/- 1.5 nM lung), ICI-215001 (5840 +/- 114 nM heart; 26100 +/- 3200 nM lung), BRL-37344 (83,300 +/- 2660 nM heart; 13,200 +/- 1250 lung). These data indicated that while levobetaxolol and betaxolol possessed a 193-233-fold selectivity for beta(1)-receptors, levobunolol exhibited a 140-fold beta(2)-receptor selectivity and (l)-timolol was essentially nonselective.

Noninvasive assessment of aqueous humor turnover in the mouse eye

PURPOSE

To develop a noninvasive test for monitoring changes in aqueous humor turnover in the mouse eye.

METHODS

After topical instillation of fluorescein, the rate of decay of fluorescence from aqueous humor and cornea was monitored in Black Swiss, C57 Bl6, and DBA 2J mice with a microscope equipped with epifluorescence and a charge-coupled device (CCD) camera.

RESULTS

The rate of decay of fluorescence was identical in right and left eyes over an approximately 70-minute measurement period. The rate of decay was similar in normal mice aged 2 and 18 months. Pilocarpine and latanoprost, known to enhance aqueous humor outflow in humans, accelerated the decay of fluorescence. Levobunolol, known to inhibit aqueous humor inflow in humans, slowed decay. Dimethylamiloride, an inhibitor of the Na(+),H(+) exchanger that is known to act on cultured cells of both the ciliary epithelium and trabecular meshwork and to lower mouse intraocular pressure (IOP), enhanced decay. DBA 2J mice, in which secondary glaucoma develops, displayed a slower decay of fluorescence at 18 months of age than age-matched unaffected animals.

CONCLUSIONS

Monitoring decay of fluorescence provides a noninvasive index of aqueous humor dynamics in the mouse eye that facilitates study of ocular hypotensive drugs and mouse models of glaucoma. Coupled with knowledge of IOP, it permits semiquantitative conclusions about the relative roles of aqueous humor inflow and outflow in conditions with altered IOP. Based on this approach, dimethylamiloride appears to lower mouse IOP primarily by enhancing outflow of aqueous humor.

[The effect of three kinds of anti-glaucoma eyedrops on ocular blood flow]

OBJECTIVE

Surveying the changes of ocular blood flow by continuous anti-glaucoma eyedrops for one week.

METHODS

Thirty-two patients in glaucoma clinic were divided into three groups, one treated by 0.5% timolol, one by 0.5% levobunolol and the third by 0.1% dipivefrine, twice a day. Each patient got the retinal and choroidal angiography before and after the medication. We also made the intra- and inter-observer reproducibility test for verifying the credibility of the method used to determine the ocular blood flow. All the data were analyzed by Students't test.

RESULTS

The reproducibility test revealed this method creditable. Timolol and levobunolol could decrease the choroidal blood flow significantly, there was a trend to decrease the optic nerve blood flow after continues application of timolol eyedrops. Dipivefrine did not induce any significant change on ocular blood flow except the mild artery constriction.

CONCLUSION

The results suggest that it is necessary to be careful in choosing the anti-glaucoma eyedrops when ischemia plays an important role in glaucomatous damage.

Ultrastructural effects of topical beta-adrenergic antagonists and an alpha-adrenergic agonist on the rabbit cornea

In the present study the effects of beta-adrenergic antagonist and alpha-adrenergic agonist drugs on rabbit corneas were evaluated in vivo by using transmission electron microscopy. Twenty-four New Zealand albino rabbits were divided into six groups according to the drug applied. The rabbits to which only balanced salt solution (BSS) or BSS and benzalkonium chloride (BAC) were applied were taken as the control groups. The other four groups consisted of the rabbits to which Timoptic 0.5%, Betagan 0.5%, Betoptic 0.5% and Iopidine 1% were applied, respectively. All of drugs were instilled topically twice daily for 6 weeks. In the BSS group, all layers of the cornea were ultrastructurally normal. In the BSS and BAC group slight epithelial and endothelial changes were found. However, in the other groups, loss of microvilli, increase in glycogen particles, nuclear indentation, widening of the intercellular spaces and cytoplasmic vacuolization in epithelium were observed. No significant abnormality was found in the basal lamina, stroma and Descemet's membrane. Slight ultrastructural changes were noted in the endothelium such as vacuolization due to dilatation of the endoplasmic reticulum cisternae and focal cytoplasmic lytic areas. The results of this study indicate that various ultrastructural changes occur in groups treated with antiglaucomatous drug and that topical treatment with timolol and apraclonidine for 6 weeks is more toxic to the rabbit cornea than levobunolol and betaxolol.

Betaxolol, a beta(1)-adrenoceptor antagonist, reduces Na(+) influx into cortical synaptosomes by direct interaction with Na(+) channels: comparison with other beta-adrenoceptor antagonists

Betaxolol, a beta(1)-adrenoceptor antagonist used for the treatment of glaucoma, is known to be neuroprotective in paradigms of ischaemia/excitotoxicity. In this study, we examined whether betaxolol and other beta-adrenoceptor antagonists interact directly with neurotoxin binding to sites 1 and 2 of the voltage-sensitive sodium channel (Na(+) channel) in rat cerebrocortical synaptosomes. Betaxolol inhibited specific [(3)H]-batrachotoxinin-A 20-alpha-benzoate ([(3)H]-BTX-B) binding to neurotoxin site 2 in a concentration-dependent manner with an IC(50) value of 9.8 microM. Comparison of all the beta-adrenoceptor antagonists tested revealed a potency order of propranolol>betaxolol approximately levobetaxolol>levobunolol approximately carteolol>/=timolol>atenolol. None of the drugs caused a significant inhibition of [(3)H]-saxitoxin binding to neurotoxin receptor site 1, even at concentrations as high as 250 microM. Saturation experiments showed that betaxolol increased the K(D) of [(3)H]-BTX-B binding but had no effect on the B(max). The association kinetics of [(3)H]-BTX-B were unaffected by betaxolol, but the drug significantly accelerated the dissociation rate of the radioligand. These findings argue for a competitive, indirect, allosteric mode of inhibition of [(3)H]-BTX-B binding by betaxolol. Betaxolol inhibited veratridine-stimulated Na(+) influx in rat cortical synaptosomes with an IC(50) value of 28. 3 microM. Carteolol, levobunolol, timolol and atenolol were significantly less effective than betaxolol at reducing veratridine-evoked Na(+) influx. The ability of betaxolol to interact with neurotoxin site 2 of the Na(+) channel and inhibit Na(+) influx may have a role in its neuroprotective action in paradigms of excitotoxicity/ischaemia and in its therapeutic effect in glaucoma.

The acute effect of topical beta-adrenoreceptor blocking agents on retinal and optic nerve head circulation

PURPOSE

Topical beta-blockers are the most common treatment for ocular hypertension in glaucoma, but their ocular hemodynamic effects are not well known. We investigated the acute effects of betaxolol (beta-1 selective antagonist), levobunolol (non-selective antagonist with active polar metabolite), and timolol (non-selective antagonist) on retinal and superficial optic nerve head circulation.

METHODS

Intraocular pressure (IOP), heart rate, blood pressure, and retinal circulation were evaluated in 12 healthy subjects (6F/6M; mean age=24+/-2 years) before and two hours after instillation of each drug on separate occasions at least two weeks apart. Macular capillary blood velocity (MCBV), epipapillary blood velocities (EBV), arteriovenous passage (AVP) times, and arterial and venous diameters were measured by digital image analysis of scanning laser fluorescein angiograms.

RESULTS

All drugs significantly (p<0.05) reduced IOP. There was no significant effect on blood pressure or calculated ocular perfusion pressure. Only levobunolol significantly lowered heart rate (p<0.05). Each drug produced a significant (p<0.01) decrease in AVP time of approximately 25%. MCBV was significantly (p<0.01) increased by approximately 20% in all three conditions; each drug also produced significant (p<0.01) increases in EBV. Arterial and venous diameters remained unaffected.

CONCLUSION

All three drugs, despite different beta-adrenergic properties, increased blood velocities in retinal and epipapillary capillaries. These changes, occurring as they do in concert with decreased retinal arteriovenous passage time at constant retinal arterial and venous diameter, may indicate improved retinal perfusion after drug treatment. Improved circulation, if it indeed occurs, in tandem with reduced IOP, might explain in part the beneficial effect of beta-adrenoreceptor blocking agents in glaucomatous patients.

Short-term effects of topical levobunolol on the human retinal circulation

PURPOSE

The effect of topical levobunolol HCl 0.5% on the retinal circulation was studied on 15 normal volunteers aged 21-54 years (32 +/- 10 years).

METHODS

In a double-masked, randomised design, one eye of each subject received a drop of levobunolol HCl 0.5% (LEV) and the fellow eye received a drop of artificial tears (TEAR). Leucocyte velocity (VBFS) and density in the retinal macular microcirculation were measured by the blue-field simulation technique. Venous diameter (D), maximum erythrocyte velocity (Vmax) and volumetric blood flow rate (Q) were measured in a major temporal vein by laser Doppler velocimetry and monochromatic fundus photography.

RESULTS

The following average changes from baseline were observed 2 hours after treatment: heart rate, -4.6 +/- 8.3% (p = 0.04); intraocular pressure, -31.7 +/- 10.6% (p = 0.0001); and perfusion pressure, 15.4 +/- 14.4% (p = 0.02) in LEV eyes; no statistically significant changes in IOP and perfusion pressure were seen in TEAR eyes. When each eye was compared with its own baseline, there were no significant changes in VBFS, density, D, Vmax and Q in LEV eyes. In TEAR eyes, there were no significant changes in VBFS, density, Vmax and Q, but a significant change in D (-1.8 +/- 2.6%; p = 0.02) was observed. A significant average percentage increase in Q of 10.9 +/- 19.2% (paired t-test between the change after LEV and the change after TEAR, p = 0.044) was seen in LEV eyes when compared with TEAR eyes. Twelve of the 15 subjects demonstrated a relative increase in Q in the LEV eyes in comparison with the TEAR eyes, while 3 subjects showed the opposite.

CONCLUSION

A significant difference in the effect of levobunolol between the two eyes was detected, even though there was no statistically significant effect when each eye was compared with its baseline.

Effect of one week of levobunolol HCl 0.5% on the human retinal circulation

PURPOSE

To determine the effect of one week of topical treatment with levobunolol HCl 0.5% on the retinal circulation of normal subjects.

METHODS

Fifteen healthy volunteers with no history of ocular disease were included in this study. In a double-masked, randomized, cross-over design, one eye of each subject was treated, for one week, with one drop of either levobunolol or placebo, administered twice daily. Following a washout period of at least three weeks, the same eye received the alternate treatment for one week. Before the beginning of therapy and then two hours after the last drop, vessel diameter (D), maximum erythrocyte velocity (Vmax), and volumetric blood flow rate (Q) were determined in one major retinal vein of the treated eye, using bidirectional laser Doppler velocimetry and monochromatic fundus photography. Statistical analysis was performed using two-tailed, paired Student's t-test, linear regression, and correlation analysis.

RESULTS

The average percentage change from baseline in intraocular pressure was statistically significant following levobunolol (-15% +/- 13% (+/-1 SD), P < .001), but not following placebo (-3% +/- 11%, P > .05). No significant changes in average D, Vmax, or Q were observed after levobunolol treatment (-1% +/- 4%, 5% +/- 11%, 4% +/- 15%, respectively) or placebo treatment (-1% +/- 4%, -2% +/- 9%, -5% +/- 10%, respectively). The average difference between the changes in Q from baseline after levobunolol and placebo treatments (9% +/- 17%) achieved a significance level of P = 0.06. Furthermore, following levobunolol treatment, Q was 7% +/- 14% higher than following placebo treatment (P = 0.05).

CONCLUSIONS

A comparison of the effects of placebo and levobunolol treatments suggests that levobunolol has a variable effect on the retinal circulation with a tendency to show an overall slight increase in flow.

Inhibitory effect of drugs with a ketone group on reduction of acetohexamide catalyzed by carbonyl reductase from rabbit kidney

The reduction of acetohexamide catalyzed by carbonyl reductase from rabbit kidney was inhibited by befunolol, moperone, levobunolol, daunorubicin and loxoprofen, which have a ketone group within their chemical structures and are substrates for the enzyme. A significant correlation was observed between the common logarithm of Vmax/Km values of the enzyme for befunolol, moperone, levobunolol and daunorubicin and the percentage inhibition of the enzyme, confirming that these drugs are competitive substrates of the enzyme with respect to acetohexamide. However, the plot for loxoprofen, a nonsteroidal anti-inflammatory drug with a ketone group, was apparently distant from the regression line obtained. Although nonsteroidal anti-inflammatory drugs with a ketone group such as suprofen and fenbufen were not reduced by the enzyme, they strongly inhibited the reduction of acetohexamide catalyzed by the enzyme.

Effects of pilocarpine and other antiglaucoma drugs on cultured human Tenon's fibroblast cells

It has been found that long-term therapy with topical antiglaucoma drugs may decrease the success of glaucoma filtering surgery. In this study, various antiglaucoma drugs, including carteolol, betaxolol, levobunolol, pilocarpine, and timolol, were investigated for their proliferative effect on cultured human Tenon's fibroblast cells. It was found that the 3H-thymidine uptake of cultured fibroblast cells was inhibited by commercial antiglaucoma drugs, including carteolol of 0.1% concentration (13%), 0.01% (50%) and 0.001% (53%), betaxolol of 0.05% concentration (14%), 0.005% (42%) and 0.0005% (62%), levobunolol of 0.05% concentration (2%), 0.005% (32%) and 0.0005% (55%), and timolol of 0.025% concentration (4%), 0.0025% (47%) and 0.00025% (55%), whereas the 3H-thymidine uptake was increased by commercial pilocarpine eyedrop from 103% (0.2% of concentration), 170% (0.02% of concentration) to 171% (0.002% of concentration), when cells were treated with commercial drugs for 100 min. Meanwhile, the proliferations of cultured fibroblast cells were stimulated by simultaneously combining 0.2%, 0.02% and 0.002% concentrations of pilocarpine eyedrops with other antiglaucoma drugs, such as carteolol of 0.1% concentration (50%), 0.01% (113%) and 0.001% (138%), betaxolol of 0.05% concentration (24%), 0.005% (128%) and 0.0005% (142%), levobunolol of 0.05% concentration (32%), 0.005% (87%) and 0.0005% (119%), and timolol of 0.025% concentration (15%), 0.0025% (94%) and 0.00025% (118%). Following incubation with pure pilocarpine, the proliferation of Tenon's fibroblast cells was inhibited for 84% (0.2% concentration), 84% (0.02% concentration) and 90% (0.002% concentration). When fibroblast cells were treated with commercial pilocarpine eyedrops for 24 hours, the 3H-thymidine uptake was increased to 160% (0.02% concentration) and 172% (0.002% concentration). This result shows that the commercial pilocarpine may play a crucial role for the proliferation of cultured human Tenon's fibroblast cells.

The effect of levobunolol hydrochloride on the calcium and potassium channels in isolated ventricular myocytes of guinea pig

The effects of levobunolol hydrochlorid (Bun) on the type L calcium channel currents (ICA) and delayed rectifier potassium channel currents (IK) in isolated ventricular myocytes of guinea pig were studied by using patch clamp whole cell recording techniques. The results were showed that: 1) Bun caused a dose dependent decrease in ICA and a dose-dependent increase in IK of the ventricular myocytes. The threshold concentrations of Bun for ICA and IK were 10(-8) mol/L and 10(-7) mol/L respectively. The maximum effective concentration of Bun for bot ICA and IK was 3x10(-5) mol/L, and half-maximal concentration was 3x10(-6) mol/L; 2) IK was blocked by 2x100(-6) mol/L tetraethylammonium (TEA). A concentration of 3x10(-6) mol/L Bun showed a decreasing effect on the ICA as revealed by the current-voltage relationship curve, i.e., Bun caused an elevation of the curve;3) When ICA was blocked by 2x10(-6) mol/L Isoptin (Verapamil), at a concentration of 3x10(-6) mol/L Bun showed an increasing effect on IK and the effect could be blocked by TEA. The above-mentioned results indicated that Bun had an inhibitory effect on ICA and a fascilitatory effect on IK. The results suggested that the molecular mechanisms of antihypertensive, heart rate slowing the beta -receptor blocking effects of Bun might be due to decrease of ICA and increase of IK.

The effect of topical beta-adrenoceptor blocking agents on pulsatile ocular blood flow

Thirty-three ocular hypertensive patients (21 with primary open angle glaucoma and 12 glaucoma suspects) were randomly assigned to receive either timolol, levobunolol or betaxolol in one eye. Pulsatile ocular blood flow (POBF) was measured before treatment (baseline) and 2 hours after drop administration. After 1 week of regular twice-daily dosage, POBF was measured again both immediately before and 2 hours after drop instillation. All measurements were made by an investigator masked to treatment. POBF increased by 11% (p = 0.09) at week 0 after levobunolol administration, and by 22% (p = 0.20) at week 1 before drop administration compared with baseline. It dropped by 23% and 25% (p = 0.04 and 0.06, respectively) before and after betaxolol administration at week 1. Although POBF was reduced in the timolol group, this change was not significant. These results can not be explained uniformly by changes in intraocular pressure or blood pressure. The relevance of these measurements to visual function in glaucoma is not known.

The effect of topical beta-blocker medications on the proliferation and viability of human Tenon's capsule fibroblasts in tissue culture

Several recent publications have suggested that the long-term use of topical antiglaucoma medications may be detrimental to the outcome of trabeculectomy. In this study we investigated the effect of topical beta-blocker medications on the proliferation and viability of human Tenon's capsule fibroblasts in tissue culture to see if there was a direct mechanism of enhanced proliferation. None of the tested medications stimulated the proliferation of fibroblasts. They were shown to have an inhibitory effect on proliferation and were toxic to cells at higher concentrations. The relevance of these findings to wound healing following trabeculectomy is discussed.

Effects of antiglaucoma medications on bovine trabecular meshwork cells in vitro

Using an in vitro culture system, we investigated the effects of five antiglaucoma drugs on growth and morphologic characteristics of bovine trabecular meshwork cells. Epinephrine hydrochloride (55-550 microM) and pilocarpine hydrochloride (0.8-16 mM), when added to the cultures for 3 days, inhibited trabecular cell growth in a dose-dependent manner. The lowest concentration at which the inhibitory effect was observed was 109 microM and 0.8 mM, respectively, for epinephrine and pilocarpine. Dipivefrin hydrochloride (26-260 microM), timolol maleate (116-1160 microM), and levobunolol hydrochloride (150-1500 microM) were also added to the cells for 3 days. These drugs caused a reduction in cell density, respectively, at concentrations higher than 103, 460, and 616 microM. Cell elongation was seen in cultures treated with epinephrine and dipivefrin, whereas levobunolol and timolol induced the cells to adopt a rounded appearance. Cells that had been exposed to pilocarpine were enlarged with numerous vacuoles. By scanning electron microscopic techniques, epinephrine, timolol, and levobunolol were found to retard the phagocytosis of latex beads by trabecular meshwork cells. Immunostaining with the use of antibodies to vimentin and actin revealed disorganization and condensation of cytoskeletal fibers in trabecular meshwork cells after treatment with epinephrine and dipivefrin. Little change was seen with comparable concentrations of a preservative, benzalkonium chloride, and a vehicle, Liquifilm tears. These results showed that antiglaucoma drugs, depending on their concentrations, may profoundly influence the growth and activity of trabecular meshwork cells.

Effects of timolol, betaxolol, and levobunolol on human tenon's fibroblasts in tissue culture

Evidence has been found suggesting that long-term therapy with topical antiglaucoma medications may decrease the success of glaucoma filtering surgery. To investigate this question further, the antiproliferative effects of the preservative benzalkonium chloride and three pure and commercially available beta-adrenergic antagonist preparations (timolol, betaxolol, and levobunolol) were studied on tissue cultures of human Tenon's capsule fibroblasts. Each drug preparation was tested on three different cell lines. Fibroblast growth was measured with tritiated thymidine uptake and hexosaminidase assays. Trypan blue uptake was used to assess cell viability microscopically. The commercially available preparations containing benzalkonium chloride and those of betaxolol and levobunolol without the preservative had similar inhibitory doses for 50% of cells. The timolol preparation without preservative was significantly less toxic than its commercially available one. The three tested beta-adrenergic blockers did not stimulate fibroblast proliferation directly in this in vitro model. Even when the cultures were washed free of the drugs, growth continued to be suppressed, suggesting that the inhibition was not reversible. An increase in fibroblasts and inflammatory cells after long-term antiglaucoma medical therapy thus may be caused not by a direct stimulation of cell proliferation but by chronic inflammation from the irritating effects of antiglaucoma medications and/or their preservatives.

[Results of the clinical study of a new adrenergic beta blocker levobunolol hydrochloride in healthy subjects and in patients with glaucoma]

Effects of a single instillation of levobunolol, a new nonselective beta-adrenoblocker, in normal subjects and patients with various forms of glaucoma were under study, as were the effects of prolonged administration of this drug in patients with open-angle glaucoma. Short-term observations have revealed a hypotensive effect in all the examinees, the highest in patients with open-angle glaucoma (30.2%). Levobunolol did not influence the diameter of the pupil and accommodation, nor did it essentially change the cardiovascular activity. Prolonged administration of the drug resulted in a stable reduction of intraocular pressure by 20-30% in 70% of patients with open-angle glaucoma. Tonographic studies have shown that the drug reduced the intraocular fluid production and in case of a prolonged administration a trend to an elevation of the coefficient of the easiness of fluid discharge is observed.

Location of penetration and metabolic barriers to levobunolol in the corneal epithelium of the pigmented rabbit

The objective of this study was to determine which of the five or six corneal epithelial layers was rate-limiting in the corneal penetration and metabolism of levobunolol in the pigmented rabbit. Corneal penetration and metabolism were evaluated using the isolated cornea in the modified Ussing chamber. Levobunolol and its metabolite, dihydrolevobunolol, were assayed by reversed phase high-performance liquid chromatography using spectrophotometric detection. EDTA (0.1 and 0.5%) and benzalkonium chloride (0.005-0.05%) were used to disrupt the integrity of the corneal epithelial layers. EDTA, which loosened the tight junctions between the superficial corneal epithelial cells, reduced both the transcorneal flux and metabolism of levobunolol. In contrast, benzalkonium chloride, which disrupted the integrity of the outermost corneal epithelial layers, enhanced the transcorneal levobunolol flux while reducing its extent of metabolism. The extent of enhancement in transcorneal flux afforded by 0.025% benzalkonium chloride was comparable to that seen in the deepithelized cornea. Within 5 min of contact by the corneal epithelium with this preservative, the ratio of dihydrolevobunolol concentration on the endothelial to the epithelial side was reduced by two-thirds. Although direct confirmation is required, the above findings are consistent with the hypothesis that the rate-limiting layer to corneal penetration of levobunolol resides in the outermost two to three layers of the corneal epithelium, whereas the metabolic barrier resides in deeper lying regions.

Cardiovascular effects of levobunolol eyedrops in healthy subjects

The cardiovascular side effects of the abrupt cessation of treatment with 0.5% levobunolol hydrochloride eyedrops in 10 healthy subjects (5 women and 5 men) aged 18 to 30 years were investigated in a double-blind randomized crossover study. The subjects received either levobunolol eyedrops or placebo drops for 7 days, then, after a 14-day washout period, they received the alternative drops for 7 days. The heart rate and blood pressure at rest, the maximal heart rate and blood pressure on treadmill exercise stress testing and duration of exercise were recorded before treatment began, at the end of treatment and 14 days after withdrawal of the drops. The mean resting heart rate was significantly lower during treatment with levobunolol than with placebo (p less than 0.05). The mean exercise duration was significantly longer during treatment with levobunolol (p less than 0.05); to our knowledge, we are the first to report this finding. There were no significant differences in mean arterial pressure, double product (product of heart rate and systolic blood pressure) or maximal heart rate between the groups at any measurement.

Effect of a beta-blocker on altered body position: induced ocular hypertension

The intraocular pressures (IOP) were measured in both eyes of 25 healthy volunteers in various body positions. One eye was pretreated with levobunolol 0.5% or placebo applied in a masked, randomised fashion, while the other served as control. IOP changes in response to levobunolol and to changes in position were significant (p less than 0.0001). However, pressure rises relative to position were not significantly different in eyes treated with drug vs placebo. Levobunolol did not alter relative changes in IOP from changes in body position. However, the overall lowering effect may offer some protection to patients with glaucoma.

Topically applied levobunolol does not cause changes in the corneal endothelium

The corneal endothelium was examined in ten patients suffering from ocular hypertension before, during and after four months of topical levobunolol treatment. The untreated fellow eye served as a control. The number of endothelial cells, determined with a McIntyre eyepiece and an Eisner's contact lens, was not affected by levobunolol therapy. In addition, the morphology of the cell did not appear to be affected by the drug.

[Local anesthetic effect and subjective tolerance of 0.5% levobunolol in normal eyes]

In a randomized, prospective, parallel double-blind clinical trial with positive and negative placebo control, the corneal sensitivity of 30 subjects with normal eyes was measured using the Cochet & Bonnet esthesiometer prior to and 1, 3, 6, 10, 15, and 30 minutes after topical application of levobunolol 0.5% (Vistagan 0.5% Liquifilm, Pharm-Allergan Vertrieb GmbH, Karlsruhe; 20 eyes). Proxymetacain 0.5% (proparacaine 0.5%, Ursapharm, Saarbrücken; 10 eyes) served as a positive, NaCl 0.9% as a negative control substance (placebo). Indomethacin 1% (Chibro-Amuno 3, Chibret Pharmazeutische GmbH, Munich; 10 eyes) was tested as a further control substance. The subjects assessed the subjective tolerance of the test substances on a 4-point scale. Levobunolol 0.5% caused a statistically significant reduction in corneal sensitivity, attaining its maximum effect in the first minute after application and lasting on average for 6 minutes. The reduction was greater than that caused by timolol 0.5% and approximately one-half of that caused by betaxolol 0.5%. Proxymetacain 0.5% reduced corneal sensitivity to below the upper limit of the Cochet & Bonnet esthesiometer (200 mg) for up to 10 minutes. After 30 minutes, corneal sensitivity reverted to its initial value in all subjects. NaCl 0.9% eye drops did not decrease corneal sensitivity. After one minute an increase in corneal sensitivity (exercise effect) was observed which was significant as compared to the initial value as of the 15th minute after application. Indomethacin 1% likewise failed to reduce corneal sensitivity. In subjects with normal eyes, levobunolol 0.5% causes only a slight reduction in sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

[Preservative-free timolol eye drops--surface-anesthetic effect and local compatibility]

0.5% timolol without preservative reduces corneal sensitivity for a shorter period of time than timolol with preservative. The subjective tolerance of unpreserved timolol is much better than that of preserved timolol. The latter and 0.5% levobunolol are significantly more poorly tolerated than buffer solution. The smaller the anesthetic side effects, the better the subjective tolerance of the beta-blockers.

Comparison of a noncardioselective beta-adrenoceptor blocker and a cardioselective blocker in reducing aqueous flow in humans

In a double-masked crossover study, the dose-response relationship for aqueous flow was determined for four concentrations of betaxolol hydrochloride and levobunolol hydrochloride in 19 normal subjects. One eye of each subject received every concentration of both drugs. Each concentration was administered once daily for 1 week. The fellow eye received a placebo. Aqueous flow was measured for several hours on the last day of administration of each concentration beginning immediately after drug administration. For levobunolol, the mean decrease in aqueous flow compared with baseline was 8% after 1 week's treatment with 0.017% levobunolol, 15% after treatment with 0.05%, 20% after treatment with 0.167%, and 32% after treatment with 0.5%. For betaxolol, the mean decrease in aqueous flow compared with baseline was 3% after 1 week's treatment with 0.017% betaxolol, 12% after treatment with 0.05%, 18% after treatment with 0.167%, and 17% after treatment with 0.5%. Levobunolol-treated eyes but not betaxolol-treated eyes showed a significant drug effect 1 week after discontinuing the drug therapy. The relative potency of the noncardioselective drug was greater than that of the beta 1-cardioselective drug, but the difference in potency was much less than would be expected solely based on their relative affinity for beta 2-receptors in other species and tissues.

The effect of timolol, betaxolol and levobunolol on the surface of rabbit cornea

Pigmented rabbits were treated with timolol maleate, betaxolol hydrochloride or levobunolol hydrochloride eye drops twice a day for six months. Animals of the same age group and breed were used as controls. There were no differences observed in corneal epithelium with light and transmission electron microscopy. With scanning electron microscopy, in the timolol and betaxolol treated animals the picture of the corneal surface was similar to that of normal rabbit corneas after exposure to air. In scanning electron micrographs of the levobunolol treated animals, the corneal surface resembled the corneas of normal rabbits treated with artificial tears.

Pharmacodynamic comparison of L-bunolol with propranolol, metoprolol, and placebo

Twelve healthy volunteers received single oral doses of propranolol (80 mg), metoprolol (100 mg), L-bunolol (2 mg), and placebo in a four-way crossover study. Blood pressure, ventricular rate, and echocardiographically determined ejection fraction, ejection time, and mean rate of circumferential fiber shortening (mVcf) were measured before dosing and at multiple time points during 10 hours after each dose, with subjects maintained in the supine position. Reductions in systolic and diastolic blood pressure following administration of each of the beta blockers were greater than those observed with placebo, but differences among the four treatments were not significant. Heart rate reductions with the beta blockers differed significantly from placebo (P less than .001), but differences among the three beta blockers were not significant. Differences among the four treatments in mVcf decrement did not attain significance at the 5% level (.05 less than P less than .1), and there were no significant differences in ejection-time prolongation or ejection-fraction reduction. Thus, reduced blood pressure, heart rate slowing, and reduced cardiac contractility may be associated with placebo treatment and may indicate the need for placebo controls in studies of the cardiovascular effects of beta blockers. Despite differing secondary pharmacologic properties, the three beta blockers reduced heart rate to a similar extent. Other effects of the beta blockers on blood pressure and cardiac contractility could not be consistently distinguished from those associated with placebo.

Ocular and cardiac beta-antagonism by timolol prodrugs, timolol and levobunolol

Topically applied O-butyryl timolol, O-pivaloyl timolol and levobunolol (0.25 micrograms) antagonized isoproterenol-induced ocular hypotension for 8 hrs whereas timolol (0.25 micrograms) was shorter acting (4 hrs). Timolol (25 micrograms) produced greater antagonism of isoproterenol-induced tachycardia than did O-butyryl and O-pivaloyl timolol (25 micrograms). These results suggest that, at similar doses, O-butyryl and O-pivaloyl timolol produce high concentrations of timolol in ocular tissues and undergo redistribution more slowly into the systemic circulation than does topical timolol. Under certain circumstances, prodrugs may provide a mechanism for increasing selectivity and extending the duration of action in the target organ as well as decreasing systemic effects.

Ocular levobunolol. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy

Levobunolol is a potent non-selective beta-adrenoceptor blocking agent used for the topical treatment of increased intraocular pressure in patients with chronic open angle glaucoma or ocular hypertension. In comparative studies of up to 2 years' duration levobunolol 0.5 to 1% reduced intraocular pressures by about 30% and adequately controlled intraocular hypertension in 50 to 85% of those treated. These results were significantly superior to those produced by placebo and comparable to the responses achieved with ocular timolol in double-blind controlled trials. Levobunolol has been well tolerated, producing only minor changes in objective and subjective ophthalmic and systemic parameters. Adverse reactions resulted in approximately 5% of patients withdrawing from treatment with levobunolol which was equivalent to that observed with timolol. Thus, ocular levobunolol is a well-tolerated and effective therapy for the management of raised intraocular pressure, and is a suitable alternative to ocular timolol in patients with chronic open angle glaucoma or ocular hypertension.

Dihydrolevobunolol is a potent ocular beta-adrenoceptor antagonist

The ocular beta-adrenoceptor antagonist activity of dihydrolevobunolol (DHLB), the major ocular and systemic metabolite of levobunolol was investigated by determining its ability to block isoproterenol-induced ocular hypotension in normotensive rabbits. Topically-applied 0.001% and 0.01% DHLB virtually abolished the response to isoproterenol, indicating a beta-blocking potency similar to that of timolol. Thus, the ocular metabolism of levobunolol leads to the formation of a highly potent beta-adrenoceptor antagonist that may contribute to its clinical efficacy.

The effect of levobunolol on aqueous humor dynamics

We evaluated the acute effects of installation of 0.5% levobunolol on aqueous humor dynamics in a double-masked study in 18 patients with ocular hypertension. Aqueous flow was measured by fluorophotometry and total outflow facility by tonography. Aqueous flow decreased approximately 29% in the eyes treated with levobunolol. Total outflow facility and episcleral venous pressure measurements were similar in levobunolol-treated eyes and contralateral eyes treated with vehicle. A 36% decrease in intraocular pressure was observed in the levobunolol-treated eyes and a slight intraocular pressure reduction was seen in the vehicle-treated eyes. The results of this study indicate that, similar to timolol, levobunolol lowers intraocular pressure primarily by decreasing aqueous humour production.

[Effect of commercial beta blockers and their combination with artificial tears on the duration of tear film stability]

The influences of 8 different beta-blockers on the tear film stability-measured on the breakup time (BUT) of normal and healthy volunteers-was compared. All beta-blockers led to BUT reduction, however, the lowest influence was observed with levobunolol. The duration of this effect was compared with that of levobunolol, timolol and metipranolol. While the minor BUT alterations induced by levobunolol recovered after 30 min and were completely restored after 1 h, those of the two other beta-blockers lasted for over 2 h. The combination of timolol 0.5% with different artificial tears containing mainly polyvinyl alcohol (PVA) 1.4%, methylcellulose and polyacrylic acid initially led also to BUT reduction. The best results were obtained with PVA 1.4%.

[Immediate effect of a topical beta-blocker on breakup time]

The comparison of different beta-blocking agents and their influences on the breakup time (BUT) reveals that levobunolol reduces the BUT in the same way as physiologic saline solutions, while other beta-blockers lead to an enormous reduction of BUT.

Influence of beta-adrenoceptor antagonists on spontaneous rate and on force of contraction of isolated rabbit atria

The influence of beta-adrenoceptor antagonists on the spontaneous rate and on force of contraction of the myocardium was studied independently on spontaneously beating right and electrically driven isolated left atria of rabbit. On spontaneous rate, practolol had sympathomimetic effect only, N-isopropylmethoxamine (IMA), had both sympathomimetic as well as depressant effects, whereas alprenolol, procinolol, bunolol and H 35/25 had depressant effects only in higher concentrations. The order of potency was procinolol greater than bunolol greater than alprenolol greater than H 35/25 greater than and IMA. On the contractions of isolated left atria, all beta-adrenoceptor antagonists produced concentration-dependent depressant effect. In relation to procinolol, these agents were 5-125 times less potent for depressing the contractions of left atria by 15% and the order of beta-potency was procinolol greater than alprenolol greater than bunolol = H 35/25 greater than IMA greater than and practolol. The present results indicate that the depressant effects of beta-adrenoceptor antagonists on spontaneous rate of right atria and on contraction of isolated left atria are not related to each other.

l-Bunolol and propranolol: oral and intravenous beta-adrenoceptor blocking activity in rats compared to dogs and humans

To determine the pharmacological significance of reported differences between species in l-bunolol metabolism, oral and intravenous beta-adrenoceptor blocking activity against an isoproterenol-induced tachycardia was compared in dogs, rats, and humans. Propranolol was similarly studied in rats and dogs. Species differences in intravenous potency were minimal for both compounds in contrast to oral dose studies. Oral to intravenous ratios of doses causing a comparable degree of beta-adrenoceptor blockade after l-bunolol were: rat, 212; dog 4; and human, 5. For propranolol, the oral to intravenous dose ratios were 210 and 32 for the rat and dog, respectively. These pharmacological findings show major differences in the rat compared to dogs and humans and may be explained in part by differences in the urinary excretion patterns of l-bunolol in the various species.

Metabolism of l-bunolol

The metabolism of l-bunolol, a new beta-blocking drug, was studied in man after single oral 3-mg doses of 3H-labeled compound. Absorption from the gut was rapid and virtually complete. Peak levels of bunolol and of dihydrobunolol, an active metabolite, were observed at 1 hr. Excretion of the administered radioactivity was mainly into the urine (78% in 4 days), with only 3% appearing in the feces. Bunolol, bunolol glucuronide, bunolol sulfate, dihydrobunolol, and dihydrobunolol glucuronide were identified and quantified in the plasma. These compounds represented 82% of the radioactivity in plasma at 30 min and 55% at 24 hr. Plasma half-lives (+/-S.D.) were estimated to be 6.1 +/- 0.3 hr for bunolol, 9.1 +/- 1.9 hr for bunolol glucuronide, 17.4 +/- 2.5 hr for bunolol sulfate, 7.1 +/- 0.5 hr for dihydrobunolol, and 7.7 +/- 0.8 hr for dihydrobunolol glucuronide.

[Effects of pretreatment with carteolol on metabolic changes induced by coronary artery ligation in dog left ventricular wall (author's transl)]

Effects of coronary artery ligation on myocardial glycogenolysis were studied in the endo- and epicardial layers of the left ventricular wall in dogs pretreated with 10 or 100 microgram/kg (i.v.) of carteolol, a potent beta-adrenergic blocking agent. Coronary artery ligation was performed by ligating one of the small branches of the left anterior descending coronary artery. In control (saline-pretreated) dogs, an increase in phosphorylase alpha activity and an increase in breakdown of glycogen were observed in both endo- and epicardial layers after coronary artery ligation. In the presence of 10 or 100 microgram/kg of carteolol, however, increases in phosphorylase alpha activity and increase in breakdown of glycogen were not observed in either the endo or epicardial layers. These results indicate that pretreatment of the dog with carteolol inhibits the increase in glycogenolysis caused by coronary artery ligation. Nevertheless, carteolol did not completely inhibit the coronary artery ligation-induced increase in glucose-6-phosphate and lactate levels, and the coronary artery ligation-induced decrease in phosphocreatine level, particularly in the endocardial layers.

Effect of a new beta-adrenergic blocker, l-bunolol, on blood pressure and on the renin-aldosterone system

The antihypertensive effect of a new beta-adrenergic receptor blocker, l-bunolol, was evaluated in 11 hospitalized hypertensive patients of whom four belonged to the high-renin, five to the normal-renin, and two to the low-renin subgroup. There was a significant decrease in blood pressure in most patients, often to normal. Moreover, plasma renin levels were nearly always markedly suppressed, and this suppression preceded the fall in blood pressure. While most high and normal renin patients responded, the numbers of patients within each subgroup were too small to correlate the blood pressure responses with changes in renin levels. There was a significant induced decrease in aldosterone excretion, which usually paralleled the renin suppression. Pulse rate was also consistently reduced during treatment. No weight gain was observed, except in one patient who developed overt congestive cardiac failure. No other side effects were recorded. Ii is concluded that l-bunolol is another beta-blocking drug with significant antihypertensive action. It was found to be effective in cases that were resistant to propranolo. It is well tolerated and safe to use, provided that early evidence of fluid retention is sought for and treated immediately.

A comparative study of the effects of OPC-1085 and propranolol on isolated guinea pig atrium

Effects of a newly synthesized beta-blocker, 5-(3-tert-butylamino-2-hydroxy) propoxy-3,4-dihydrocarbostyril (OPC-1085) were compared with those of propranolol. OPC-1085 had a potency about 3 times greater than that of propranolol in blocking the positive inotropic and chronotropic effects of isoprenaline on the isolated guinea pig atrium. At a concentration of over 3 X 10(-5) M OPC-1085 produced negative inotropic and chronotropic effects. However, these effects were about 10 times weaker than those of propranolol. Suppressing effects on the rate of rise and on the maximum driving frequency of action potentials were also more than 10 times less than those of propranolol. There was almost no change in the action potential of vagus nerve after a 10 min treatment with OPC-1085 (10(-5) M), while the action potential was reduced to 60-70% with propranolol (10(-5) M).

[A comparison of the effects of the beta-adrenergic blockers, carteolol (OPC-1085), propranolol and alprenolol on isolated rat cardiac muscles (author's transl)]

The effects of carteolol, propranolol and alprenolol were studied by using spontaneously contracting atria, atrial muscle and papillary muscle prepared from rat hearts. Propranolol, alprenolol and carteolol caused decreases in atrial rate and in contractile tension of electrically driven cardiac muscles in concentrations of 10(-6) to 10(-5) g/ml, 10(-6) to 10(-5) g/ml and 10(-4) g/ml, respectively. These compounds, also, effectively prevented electrically-induced atrial arrhythmias in these concentrations. Contractile tension of the cardiac muscles was increased by carteolol in concentrations of 10(-7) to 10(-6) g/ml. The refractory period of the cardiac muscles was prolonged in the presence of alprenolol (10(-7) to 10(-6) g/ml) or carteolol (10(-6) to 10(-5) g/ml). The refractory period of the papillary muscle was increased by 10(-7) to 10(-6) g/ml of propranolol. The maximum driven frequency (MDF) of the atrial muscle was reduced by 5X10(-8) to 10(-7) g/ml of carteolol or by 5X10(-8) g/ml of alprenolol, and MDF of the papillary muscle by 5X10(-7) g/ml of propranolol. In extremely high concentrations, these compounds significantly reduced MDF of the cardiac muscle. These results suggest that the antiarrhythmic action of alprenolol and carteolol is more predominant in atria than in ventricles, whereas the reverse is true for propranolol.

Levo-bunolol and propranolol: further evaluation of oral beta-blocking activity in conscious dogs

The oral beta-adrenoceptor blocking activity of bunolol, propanolol, and their levo-isomers was compared against isoproterenol- and treadmill exercise-induced tachycardias in normal conscious dogs. Relative potencies against isoproterenol were (ascending order): propranolol=1, levo-propranolol=2, bunolol=40, and levo-bunolol=102. Large oral doses of levo-bunolol and propranolol suppressed exercise tachycardia by only 18% (range 10 to 22%). Compared to the isoproterenol response, the tachycardia associated with severe exercise in the healthy trained dog was largely resistant to beta-receptor blockade showing factors other than beta-receptor stimulation to be involved. Differences in duration of beta-blockade were observed at equiactive doses of levo-bunolol and propranolol. The isoproterenol response had returned to greater than 50% of control by 12 hr after propranolol but was less than 10% of control at 12 hr after levo-bunolol. The time to 50% recovery of the exercise tachycardia was 24 hr after levo-bunolol and 6 to 9 hr after propranolol. The results show oral levo-bunolol to be considerably more potent and to have a longer duration of action than propranolol in inhibiting both isoproterenol and exercise-induced tachycardias in conscious dogs.