The intraocular pressure lowering effect of timolol in gel-forming solution

Improved ocular absorption kinetics of timolol maleate loaded into a bioadhesive niosomal delivery system

BACKGROUND

Application of timolol maleate (TM) in a conventional dosage form (solution) into the eye results in almost 80% of the instilled dose being lost either through spillage or due to drainage into the nasolacrimal duct. Later results in systemic side-effects especially in patients suffering from heart diseases or bronchial asthma thus limiting the usefulness of TM for the control of glaucoma. Earlier we had reported on the development of a mucoadhesive coated niosomal system for TM (TM REV(bio)) containing 0.25% TM. Presently we establish and report the pharmacokinetic and pharmacodynamic superiority of the developed ocular formulation of TM.

METHODS

Aqueous humor concentration of TM in male albino rabbits, after instillation of one drop of TM solution (TMS) or TMREV(bio) was measured using the microdialysis method.

RESULTS

Peak concentration of drug in aqueous humor from TMREV(bio) (12.46 microg/ml achieved at 60 min) was almost 1.7 times that of the control drug solution (TMS, 0.25%; 7.2 microg/ml). An important observation was that the high drug concentrations achieved upon TMREV(bio) administration were maintained for up to 2 h. AUC for TMREV(bio) formulation was 2.34 times that of the TMS.

CONCLUSIONS

This study confirms a sustained and controlled effect of the developed formulation.

Barriers to glaucoma drug delivery

Topical medications remain the mainstay of glaucoma treatment. This review will aim to cover the pharmacokinetics of topically applied drops, the ocular barriers to drug delivery, and the role of ophthalmic drug formulation in enhancing drug delivery to the target tissue while minimizing side effects and increasing patient compliance. Recent advances in surgical techniques, therapeutic approaches, and material sciences have produced exciting new therapies for ocular diseases. The development of new vehicles and drug formulations that require less patient compliance is also discussed, as are the routes of drug delivery for neuroprotection.

Study of the extent of ocular absorption of acetazolamide from a developed niosomal formulation, by microdialysis sampling of aqueous humor

Acetazolamide, a carbonic anhydrase inhibitor is used orally (no topical formulation being available in the market) for the reduction of intraocular pressure (IOP) in patients suffering from glaucoma. Two major reasons responsible for the failure to develop a topically effective formulation of acetazolamide are its low solubility (0.7mg/ml) and its low permeability coefficient. It is generally recognized that topical acetazolamide formulation possessing efficacy similar to that achieved upon oral administration would be a significant advancement in the treatment of glaucoma. In order to enhance the bioavailability of acetazolamide by topical route and to improve the corneal permeability of the drug, the niosomes of acetazolamide were prepared (by reverse phase evaporation method) and coated with Carbopol for the latter's bioadhesive effect. The pharmacodynamic studies showed 33% fall in IOP with the developed formulation, and the effect was sustained for 6h after instillation. The effect compared well with a four times higher concentration of dorzolamide (Dorzox, a topical CAI available in the market. In the present study, the aqueous humor disposition of the drug from the developed bioadhesive coated niosomal formulation (ACZREVbio) is compared with the aqueous suspension of the drug (containing 1% (w/v) Tween 80 as a dispersing agent) at similar concentrations. The concentration of acetazolamide absorbed in the aqueous humor at various times from the control suspension and from ACZREVbio was determined by microdialysis in male albino rabbits. Microdialysis provides a complete concentration versus time profile and hence is an important advance to the regional sampling of tissues. The peak concentration of drug absorbed in the aqueous humor from the ACZREVbio formulation (14.94microg/ml) was almost two times of that obtained with the equivalent amount of acetazolamide control suspension (6.93microg). The results show a significant broadening of peak from 80 to 120min with the concentration of more than 13microg being maintained at these times, for the bioadhesive coated niosomal formulation (ACZREVbio). An important observation was the fact that a high drug concentration of 12.02microg reached immediately, i.e., 20min after instillation of ACZREVbio indicating a high penetration being achieved, while a meagre concentration of only 3.53microg is obtained at 60min after instillation of the control suspension. The aqueous humor disposition indicates peaks and troughs in drug concentration which may be related to the decrease in aqueous humor formation, such that the drug concentration/volume increased at these points.

The Effects of a Timolol Maleate Gel-Forming Solution on Normotensive Beagle Dogs

The effects of a timolol maleate gel-forming solution (TMGS) on intraocular pressure (IOP), blood pressure (BP), and pupil size (PS) were evaluated in normotensive dogs. TMGS was administered once daily to six normotensive beagle dogs. TMGS administration reduced IOP and PS. The hypotensive effect persisted for 24 hr after the administration. The mean reduction in IOP was 5.3 mm Hg (P<0.01). The changes in BP and PS were not significant. These results suggest that TMGS can potentially be used in the treatments of glaucoma and ocular hypertension in dogs.

The efficacy of timolol in gel-forming solution after morning or evening dosing in Asian glaucomatous patients

AIMS

The aim of this study was to determine the effectiveness of timolol gel-forming solution as a monotherapy and to compare the efficacy of timolol gel-forming solution morning instillation versus at night application in Asians with newly diagnosed open-angle glaucoma.

METHODS

A retrospective, comparative, parallel group study was conducted on 78 eligible patients diagnosed with open-angle glaucoma who received topical timolol gel-forming solution either on morning (AM dosing group; 39 patients) or evening (PM dosing group; 39 patients) as monotherapy treatment. Intraocular pressure was taken at baseline, 1, 3, 6, and 12 months post-treatment.

RESULTS

Mean baseline intraocular pressure (IOP) for timolol gel-forming solution in general was 22.7 +/- 6.6 mmHg with the mean IOP reduction of 5.7 +/- 5.3 mmHg (23.1% reduction). The mean IOP reduction of the AM dosing group was 7.5 +/- 5.2 mmHg (31.0% reduction) and 3.9 +/- 4.9 mmHg (15.1% reduction) in the PM dosing group (P = 0.0002). There was a statistically significant difference of IOP reductions between AM and PM dosing group at 1 month (P = 0.041), 3 months (P = 0.037) and 12 months (P = 0.015) post-treatment. Seventy-five percent (24) of good responders was in the AM group and 67.4% (31) of poor responders were patients in the PM group.

CONCLUSION

Timolol gel-forming solution is effective in reducing IOP in Asian eyes. Morning dosing was more effective in lowering the IOP compared to evening dosing.

Improved pharmacodynamics of timolol maleate from a mucoadhesive niosomal ophthalmic drug delivery system

In the present study chitosan (REVTMbio1) or Carbopol (REVTMbio2 and 3) coated niosomal timolol maleate (0.25%) formulations were prepared by reverse phase evaporation (REV) and compared to timolol solution (TMS; 0.25%) in terms of in vitro release and IOP lowering pharmacodynamic effect. The in vitro release phase of timolol (91% release in 2 h) was extended significantly by its incorporation into niosomes and further by the polymer coating (40-43% release upto 10 h). The developed formulations were evaluated for their pharmacodynamics in albino rabbits, by measuring intraocular pressure (IOP) using a non-contact pneumatonometer, and were compared to a marketed in situ gel forming solution of timolol (Timolet GFS, 0.5%; Sun Pharma). REVTMbio1 formulation showed a more sustained effect of upto 8h (vis a vis 6 h for carbopol-coated niosomes). TMS in comparison showed effect for only 2 h though the peak effect was slightly more (14%). Lowering of IOP in the contralateral eye (20-40% as compared to 100% in case of TMS), considerably reduces with REV and REVbio formulations indicating lesser systemic side effects. Moreover, the results of REVTMbio1formulation containing 0.25% of timolol maleate compared well with the 0.5% marketed gel formulation, indicating our formulation to be significantly better considering that similar effect is obtained at half the concentration. The later becomes especially important in context to the cardiovascular side effects associated with ocular timolol maleate therapy.

Comparison of the nocturnal effects of once-daily timolol and latanoprost on intraocular pressure

PURPOSE

To compare the nocturnal effects of once-daily timolol and latanoprost on intraocular pressure (IOP) in patients with ocular hypertension or early glaucomatous changes.

DESIGN

Prospective, open-label, experimental study with crossover design.

METHODS

Eighteen patients with ocular hypertension or early glaucomatous changes (aged 41 to 79 years) each received topical treatments with timolol (0.5% Timoptic-XE), latanoprost (0.005% Xalatan), and no IOP-lowering medication, for at least 4 weeks. Timolol was given once in the morning upon awakening and latanoprost once in the evening at bedtime. At the end of each treatment period, the patient was housed in a sleep laboratory for 24 hours and IOP was measured every 2 hours using a pneumatonometer. Measurements were taken sitting and supine during the 16-hour diurnal/wake period and only supine during the 8-hour nocturnal/sleep period. Mean diurnal and nocturnal IOP levels were compared among the treatments with timolol, latanoprost, and no medication.

RESULTS

In the diurnal period, the mean IOP under the timolol or the latanoprost treatment was significantly less than the mean IOP under no medication in both the sitting and the supine positions. There was no statistical difference between the timolol and latanoprost treatments. In the nocturnal period, supine IOP with timolol treatment was not different from the supine IOP with no medication but was significantly higher than supine IOP with the latanoprost treatment.

CONCLUSION

Although both once-daily timolol and latanoprost were effective in lowering IOP during the diurnal period, only latanoprost reduced IOP during the nocturnal period.

Comparison of aqueous and gellan ophthalmic timolol with placebo on the 24-hour heart rate response in patients on treatment for glaucoma

PURPOSE

Topical beta-blocker treatment is routine therapy in the management of patients with glaucoma. Therapy results in systemic absorption, however, the degree of reduction of resting and peak heart rate has not been quantified.

DESIGN

This trial evaluated the effect of placebo, 0.5% aqueous timolol (timolol solution) and a 0.5% timolol suspension that forms a gel on application to the conjunctiva (timolol gellan) on the 24-hour heart rate in patients currently being treated for glaucoma to quantify the reduction in mean heart rate.

METHODS

Forty-three Caucasian patients with primary open-angle glaucoma or ocular hypertension with a mean (+/-SD) age of 63 (+/-8) years were randomized and crossed over in a double-masked manner to 14 days of treatment with placebo (morning and evening in both eyes), timolol solution (morning and evening in both eyes), or timolol gellan (morning in both eyes with placebo in the evening). On the 13th day of each period, heart rate was recorded continuously during a typical, ambulant 24-hour period.

RESULTS

Both timolol solution and timolol gellan reduced the mean 24-hour heart rate compared with placebo (P < or = .001), and this reduction was most pronounced during the daytime (-7.5% change in mean heart rate, -5.7 beats/min). Timolol gellan showed a numerically but not significantly smaller reduction in 24-hour heart rate, compared with timolol solution. During the night, the mean 12-hour heart rate on placebo and timolol gellan were both significantly less than on timolol solution; the difference between solution and gellan treatments was statistically significant (P = .01).

CONCLUSIONS

Both timolol solution and timolol gellan decrease the mean 24-hour heart rate compared with placebo. This response was most pronounced during the active daytime period. These data quantify the modest bradycardia associated with ophthalmic beta-blocker therapy in a typical patient population on therapy for glaucoma. Although exercise performance was not assessed in this trial, reductions of this magnitude should not have substantial clinical consequences.

Ocular hypotensive efficacy and safety of once daily carteolol alginate

BACKGROUND/AIM

Carteolol is a beta adrenoceptor antagonist used topically to reduce intraocular pressure, typically twice daily. In an effort to provide a once daily dosing regimen, carteolol was formulated with 1% alginic acid. The objective of this study was to evaluate the efficacy and safety of carteolol alginate solution in comparison with standard carteolol solution.

METHODS

This was a double masked, parallel group, multicentre study. Patients with ocular hypertension or open angle glaucoma (n=235) were randomly assigned to receive either carteolol alginate once daily [corrected] or standard carteolol solution, twice daily. The masking was maintained through the use of a vehicle in the evening for the alginate group. Patients were evaluated at baseline, 15, 60, and 120 days.

RESULTS

At 0900 (presumed trough) on day 60, mean reductions in intraocular pressure (IOP) from baseline were 6.09 (SD 2.97) and 6.09 (3.18) mm Hg for the standard carteolol and alginate, respectively. At 1100 (presumed peak), mean reductions were 6.51 (2.53) and 6.47 (2.76) mm Hg, respectively. Results were similar at other times (day 15 and day 120). The most common side effect was transient stinging on instillation of drops, which did not differ significantly between groups. There were no differences of note in other ocular or systemic signs or symptoms.

CONCLUSION

The new alginate formulation of carteolol 2% given once daily was as effective as standard carteolol 2% given twice daily with no meaningful differences regarding safety.

Management of glaucoma in pregnancy and lactation

A 30-year-old pregnant woman with glaucoma is presented. The management of her case is used as a basis for a discussion of the use of glaucoma medications, including newer formulations, during pregnancy and lactation.

Efficacy and tolerability of timolol maleate ophthalmic gel-forming solution versus timolol ophthalmic solution in adults with open-angle glaucoma or ocular hypertension: a six-month, double-masked, multicenter study

BACKGROUND

Timolol has been formulated in a highly purified gellan gum to improve its duration of action. The efficacy of this formulation in short-term studies using once-daily dosing has been reported.

OBJECTIVE

The purpose of this study was to evaluate the efficacy and tolerability of 0.5% timolol maleate ophthalmic gel-forming solution (timolol GS) given once daily versus 0.5% timolol solution given twice daily in a long-term trial.

METHODS

This was a multicenter, double-masked, 6-month trial. After a washout of ocular hypotensive medication, 286 patients with open-angle glaucoma or ocular hypertension were randomly assigned in a 2:1 ratio to receive 0.5% timolol GS in both eyes once daily or 0.5% timolol solution in both eyes twice daily. All patients received a morning (9 AM) and evening (9 PM) dose. For patients in the timolol GS group, the evening dose consisted of a vehicle only, whereas for patients in the timolol solution group, both doses consisted of active drug. Intraocular pressure (IOP) was measured at trough (before morning instillation) and peak (2 hours after instillation) at follow-up examinations at weeks 2, 4, 8, 12, and 24. Adverse events were monitored using patient reports.

RESULTS

Of the 286 patients randomized, 191 received timolol GS and 95 received timolol solution. Ninety-three percent of patients (265/286) completed the study. At the end of the treatment interval (week 24), the mean decrease in IOP at trough ranged from 5.6 to 5.9 mm Hg in the timolol GS group and from 6.3 to 6.6 mm Hg in the timolol solution group. Similar efficacy was observed at 11 AM (peak). At week 24, the difference in mean IOP between treatments was -0.61 mm Hg (95% CI -1.44 to 0.22) at trough and -0.79 mm Hg (95% CI -1.77 to 0.20) at peak, indicating no significant difference between the 2 timolol formulations. The number of reports of blurred vision and tearing was significantly higher in the timolol GS group than in the timolol solution group (P = 0.04), whereas burning/stinging was reported more frequently in the timolol solution group than in the timolol GS group (P = 0.04). At week 12, the decrease in mean heart rate at trough (hour 0) was significantly less for patients in the timolol GS group than for those in the timolol solution group (-1.1 vs -4.2 bpm; P = 0.024). At week 24 (hour 0), the decrease in mean heart rate was less for patients treated with timolol GS by 2.5 bpm (P = 0.051). The heart rate data at peak (hour 2) was similar to that observed at trough at week 12 (-2.7 vs -5.7 bpm; P = 0.006) and week 24 (-3.1 vs -4.7 bpm; P = 0.063). The mean change in blood pressure was not significantly different between treatments. There were no clinically significant differences between the groups in visual acuity, biomicroscopy and ophthalmoscopy results, or visual fields.

CONCLUSIONS

Timolol 0.5% GS administered once daily was shown to be as effective in lowering IOP as the equivalent concentration of timolol 0.5% solution administered twice daily in patients with ocular hypertension or open-angle glaucoma.

Long-term intraocular pressure-lowering efficacy and safety of timolol maleate gel-forming solution 0.5% compared with Timoptic XE 0.5% in a 12-month study

PURPOSE

To evaluate the long-term intraocular pressure-lowering efficacy and safety of timolol maleate gel-forming solution 0.5% (Timolol GFS 0.5%, Alcon Research Ltd, Fort Worth, Texas) compared with Timoptic XE 0.5% (Merck, Inc, West Point, Pennsylvania) in patients with open-angle glaucoma or ocular hypertension.

METHODS

Two hundred forty-one patients with open-angle glaucoma or ocular hypertension, who had intraocular pressure between 22 and 36 mm Hg in at least one eye, were randomly assigned in a 2:1 ratio to receive either Timolol GFS 0.5% once daily or Timoptic XE 0.5% once daily, in a 12-month randomized, multicenter, double-masked, prospective study. The primary efficacy variable was mean trough intraocular pressure measured at 8:00 AM, approximately 24 hours after dosing.

RESULTS

The Timolol GFS 0.5% group produced significant trough intraocular pressure reductions from a baseline of 4.5 to 5.2 mm Hg (P =.0001), compared with reductions of 4.1 to 5. 3 mm Hg (P =.0001) in the Timoptic XE 0.5% group. The difference in mean intraocular pressure between the two treatments was 0.9 mm Hg or less, and the upper 95% confidence limit between groups was 0.92 mm Hg or less at all time points, demonstrating both clinical and statistical equivalence. A similar percentage of patients in the Timolol GFS 0.5% group (71%) and Timoptic XE group (72%) had clinically relevant reductions in intraocular pressure. There was no significant difference in the safety profiles of the two treatments.

CONCLUSION

Both treatments were clinically effective in lowering intraocular pressure and maintaining the reductions over long-term use. Timolol GFS 0.5% is a safe and effective therapy for open-angle glaucoma or ocular hypertension and is both clinically and statistically equivalent to Timoptic XE 0.5% in reducing intraocular pressure.

Timolol lowers intraocular pressure but does not inhibit the development of experimental myopia in chick

Reports of intraocular pressure (IOP) being higher in myopes than emmetropes and of myopes being over-represented in glaucoma statistics, are consistent with a role of IOP in the excessive eye growth typically associated with myopia. We tested the hypothesis, based on these observations, that ocular hypotensive drugs would slow myopia progression using the chick as an animal model and timolol as an example of such a drug. To induce myopia, chicks (n = 56) were fitted with either monocular translucent diffusers or -15 D spectacle lenses from day 8. The drug treatment protocol comprised topical applications of 0.4% benoxinate, a local anaesthetic (to improve drug absorption), followed either by 0.5% timolol or distilled water (control), either daily (1000 hr) or twice daily (1000, 1600 hr). Refractive errors and ocular dimensions were measured on days 12 and 17. We also verified the ocular hypotensive effect of timolol in both normal (n = 8) and myopic (n = 12 diffusers; n = 12-15 D lenses) chicks. Here, we took baseline IOP measurements, instilled timolol and then monitored IOP over a further 5-9 hr. We found no difference in the amount of myopia produced in the timolol and control groups at either measurement time point (e.g. day 17, once per day application, diffusers: -26.9 +/- 3.3 D vs -22.7 +/- 9.1 D; lenses: -14.9 +/- 3.8 D vs -14.9 +/- 3.6 D). This was in spite of the fact that timolol did lower IOP in both normal and myopic chicks (27 and 18% reduction, respectively) While timolol does have an ocular hypotensive effect in the chick, it does not inhibit the development of myopia in this animal model.

Efficacy and tolerability of 0.5% timolol maleate ophthalmic gel-forming solution QD compared with 0.5% levobunolol hydrochloride BID in patients with open-angle glaucoma or ocular hypertension

We compared the efficacy of timolol maleate ophthalmic gel-forming solution 0.5% QD with that of levobunolol hydrochloride 0.5% BID, as measured by change in intraocular pressure (IOP), effect on heart rate, and ocular tolerability. The study had a positive-controlled, double-masked, randomized, multicenter, 12-week, two-period (6 weeks each), crossover design. One hundred fifty-two patients with open-angle glaucoma or ocular hypertension were randomized to receive either timolol maleate gel-forming solution QD or levobunolol BID for 6 weeks, followed by a crossover to the alternate treatment. IOP and heart rate were measured at morning trough and peak during weeks 3, 6, 9, and 12. Timolol maleate gel-forming solution QD was comparable to levobunolol BID in reducing IOP at peak and trough. Although the effects on peak heart rate were similar between the two medications, the effect on trough heart rate of timolol maleate gel-forming solution QD was significantly less than that of levobunolol BID (P = 0.001). The incidence of ocular burning and stinging was comparable between the two treatments. Patients experienced significantly more blurred vision when using timolol maleate gel-forming solution than when using levobunolol (P = 0.013). Overall, more patients experienced at least one adverse event when using timolol maleate gel-forming solution. Timolol maleate gel-forming solution QD is as efficacious in reducing IOP as levobunolol BID.