Poly(2-hydroxyethyl methacrylate) film as a drug delivery system for pilocarpine

This work investigates pilocarpine trapped in a matrix diffusion-controlled drug delivery system using hydrophilic inserts of Poly(2-hydroxyethyl methacrylate) (pHEMA) to ensure an increased bioavailability of pilocarpine and prolong the length of time in which the medication remains in the eyes of the test subjects. The physical and chemical properties of pilocarpine were investigated to elucidate the mechanism of drug-polymer interaction and the effect on drug release behavior of controlled release polymeric devices. In vitro release studies indicated that pilocarpine continued to be released from the inserts for a 24 h period. The results of intraocular pressure tests performed on albino rabbits were consistent with the observed in vitro behavior. The pressure decrease was significant for a period longer than 48 h. It confirms that the inserts, as sustainable releasing devices, are promising carriers for ophthalmic drug delivery systems.

Pluronic F127-based ocular delivery system containing biodegradable polyisobutylcyanoacrylate nanocapsules of pilocarpine

The objectives of our study were to prepare a biodegradable polyisobutylcyanoacrylate (PIBCA) colloidal particulate system of pilocarpine, to incorporate it into a Pluronic F127(PF127)-based gel delivery system, and to evaluate its ability to prolong the release of pilocarpine. Polyisobutylcyanoacrylate nanocapsules (PIBCA-NC) of pilocarpine were prepared by interfacial polymerization. Physicochemical characterization of the colloidal dispersion of PIBCA-NC of pilocarpine was performed by measuring drug loading, particle size analysis, and scanning electron microscopy. Results indicated that approximately 13.5% of pilocarpine was loaded onto the PIBCA-NC, the nanocapsules ranged from 370 to 460 nm, the distribution was narrow, and there was no significant effect of stirring speed on particle size. The PIBCA-NC dispersion of 1% pilocarpine alone (I) and after incorporation into the Pluronic F127 gel delivery system (II) were compared against 1% pilocarpine incorporated into a PF127 gel containing 5% methylcellulose (PF127MC) alone (III) by measuring the miotic response in the albino rabbit eye. Statistical analysis indicated a rank-order for both the duration and intensity of miosis of II > III >> I, with all differences being significant (p < 0.05). Thus, it appears that II increases the contact time of pilocarpine with the absorbing tissue in the eye, thereby improving ocular bioavailability. The PIBCA-NC of pilocarpine dispersed in the PF127MC gel delivery system has considerable potential for achieving a prolonged delivery for such drugs as pilocarpine and other more hydrophobic drugs.

Effect of decreased retinal illumination on frequency doubling technology

PURPOSE

To investigate the effect of changes in retinal illumination on Frequency Doubling Technology (FDT).

METHODS

Five eyes, of 5 adults who were free from identifiable ocular pathology, were examined using the Snellen chart and the Pelli-Robson chart, conventional automated perimetry, and the full threshold N-30 program of FDT. Each test was performed with and without a 0.9, 1.5, or 2.4 log unit neutral-density (ND) filter placed before the eye. Furthermore, the influence of pupil diameter on FDT test results was compared after treatment with pilocarpine or cyclopentolate with the influence of ND filters.

RESULTS

All tests showed a decrease in sensitivity with decreasing retinal illumination. Frequency Doubling Technology showed an especially pronounced and significant decrease in sensitivity. The maximum mean threshold difference in FDT results with ND filter was 31.2 dB while that with the Humphrey Field Analyzer and the Pelli-Robson chart were 13.3 dB and 0.66 log contrast, respectively. The mydriatic state of the pupil increased the sensitivity of FDT and the miotic state decreased it to about the same extent as the the 0.9 ND filter.

CONCLUSION

The change in retinal illumination has more impact on FDT than on spatial contrast tests and conventional automated perimetry. It is important to take this into account in evaluating FDT results.

Bilateral angle closure glaucoma and visual loss precipitated by antidepressant and antianxiety agents in a patient with depression

A 71-year-old woman with depression had been treated with an antidepressant (maprotiline) and antianxiety agents (clotiazepam and alprazolam). She had previously complained of ocular pain and blurred vision. However, thorough ocular examination was not performed at those times. On examination, visual acuity was no light perception OD and hand motion OS. Intraocular pressures were 33 mm Hg OU. Moderately dilated pupils, atrophic irises, shallow anterior chambers and closed angles were seen in both eyes. Despite treatment, her visual acuity decreased to no light perception bilaterally. Psychiatrists and ophthalmologists should be aware that antidepressants and antianxiety agents can precipitate angle closure glaucoma in susceptible eyes.

The efficacy of topical prophylactic antiglaucoma therapy in primary closed angle glaucoma in dogs: a multicenter clinical trial

The ability of either 0.5% betaxolol (1 drop topically, bid; n=31) or a combination of 0.25% demecarium bromide and a topical corticosteroid (gentamicin/betamethasone) (DB/GB; 1 drop of each topically, sid; n=55) to prevent glaucoma in the fellow eye of dogs with unilateral, primary closed angle glaucoma (PCAG) was investigated in a multicenter, open-label, clinical trial. Untreated control dogs (n=20) developed glaucoma significantly sooner (median, eight mos; p less than 0.001) than dogs treated either with DB/GB (median, 31 mos) or betaxolol (median, 30.7 mos). Although DB/GB and betaxolol equally delayed or prevented the onset of glaucoma in the second eye, a less frequent dosing schedule for DB/GB suggests demecarium bromide in combination with a topical corticosteroid may be preferable to betaxolol in preventing PCAG in dogs.

Effect of intraocular acetylcholine and carbachol on the corneal endothelium. In vivo comparative study

The purpose of this study is to evaluate differences in corneal endothelial cell loss after intraocular use of two different miotics in subjects who have undergone extracapsular cataract extraction with posterior chamber intraocular lens implantation. The patients were divided into two groups: the first received 1 ml of 1% acetylcholine chloride and the second 0.5 ml of 0.01% carbachol as intraocular miotics. The endothelial count was done preoperatively and then 1 month after cataract extraction. There were no statistically significant differences in the mean cell loss between both groups. The authors believe that both miotics could be used in cataract surgery.

Effect of calcium channel blockers alone and in combination with antiglaucoma medications on intraocular pressure in the primate eye

PURPOSE

To determine the effect of representative members from six classes of calcium channel blockers on intraocular pressure in the primate eye. Other antiglaucoma medications were administered with verapamil to determine their combined effect on intraocular pressure.

METHODS

Six healthy cynomolgus monkeys were anesthetized, and baseline intraocular pressure was measured. Drug-containing solution (50 microL) was instilled in one eye and intraocular pressure was measured in both eyes 90 minutes later.

RESULTS

All classes of calcium channel blockers significantly lowered intraocular pressure in the treated eye. The percent reduction in intraocular pressure compared with the baseline pressure was 10% for verapamil (P < 0.002), 18% for nifedipine (P < 0.001), 15% for diltiazem (P < 0.001), 17% for flunarizine (P < 0.001), 19% for prenylamine (P < 0.001), and 6% for perhexiline (P < 0.01). In the fellow eye, a significant reduction in intraocular pressure was also seen with all calcium channel blockers except perhexiline, which suggested a crossover effect. In contrast, neither vehicle treated nor contralateral eyes showed a lowering of intraocular pressure when tested under the same conditions. In the treated eye, 0.5% timolol (P < 0.01) and 0.05% clonidine (P < 0.02) combined with 0.25% verapamil each appeared to produce an additive effect, with a significantly greater pressure-lowering effect than either agent alone. In addition, 0.005% pilocarpine (P < 0.001) and 0.00125% demecarium (P < 0.01) combined with 0.25% verapamil each appeared to produce a synergistic effect, with a significantly greater reduction in intraocular pressure than both agents combined.

CONCLUSIONS

Topical calcium channel blockers and combinations of verapamil with antiglaucoma medications may provide a useful alternative for reducing intraocular pressure in patients with ocular hypertension or primary open-angle glaucoma.

Increased partitioning of pilocarpine to the oily phase of submicron emulsion does not result in improved ocular bioavailability

Submicron emulsions containing pilocarpine as ion-pair with mono-dodecylphosphoric acid were prepared. Physical stability of these preparations was confirmed during 4 months of storage at 4 degrees C. Approximately 50% of the drug was found in the aqueous phase of emulsion separated using an ultrafiltration technique, while the rest was present in the oily phase and interphase. The miotic effect observed in rabbits after application of the ion-pair in aqueous solution or in submicron emulsion was the same; indicating that the drug distribution into the oily phase of the colloidal vehicle does not improve ocular bioavailability.

The additive intraocular pressure-lowering effect of latanoprost 0.005% daily once and pilocarpine 2% t.i.d. in patients with open-angle glaucoma or ocular hypertension. a 6-month, randomized, multicenter study. German Latanoprost Study Group

PURPOSE

To compare the additional intraocular pressure-lowering effect of latanoprost 0.005% administered once daily with that of pilocarpine 2% administered three times daily in patients with primary open-angle glaucoma or ocular hypertension currently on monotherapy with timolol 0.5% twice daily.

METHODS

In a 6-month, multicenter, randomized, open-label study 242 patients with POAG or OH whose IOP was not controlled with timolol 0.5% b.i.d. were enrolled. Eyes had not been treated with pilocarpine and latanoprost for at least 2 years. An analysis of covariance with diurnal IOP change from baseline to month 6 for study eyes was performed.

RESULTS

Four patients on latanoprost 0.005% and 35 on pilocarpine 2% did not complete the study (P<0.001). Two hundred and forty patients were included in the intent-to-treat analysis. For both treatments the diurnal IOP reduction after 6 months was statistically significant (P<0.001). IOP (mean+/-SD) was reduced from 23.3+/-2.8 to 17.8+/-2.8 (-5.6) mmHg in the latanoprost 0.005% group and from 23.0+/-3.2 to 18.5+/-2.4 (-4.8) mmHg in pilocarpine 2% t.i.d.-treated eyes. The mean difference of -0.8 mmHg (per protocol, PP) and -1.6 mmHg (intend-to-treat, ITT) was statistically significant (P<0.04, PP; P<0.001, ITT) in favor of latanoprost 0.005%. Two eyes treated with latanoprost showed an iris color change. Thirty-six patients in the latanoprost group and 106 in the pilocarpine 2% group reported ocular adverse events (P<0.001).

CONCLUSION

From the data we conclude that the additivity of latanoprost 0.005% is at least as effective as pilocarpine 2% t.i.d. in reducing IOP when added to eyes currently on monotherapy with timolol 0.5% b.i.d. Latanoprost was better tolerated than pilocarpine 2% eye drops in this study. The increase in iris pigmentation requires further investigation.

Ophthaproblem. Acute angle-closure glaucoma

Images

[Therapy of primary open-angle glaucoma by oftan-dipivefrin]

Choice of optimal hypotensive therapy with the minimal side effects remains a serious problem in therapy of glaucoma. The efficacy and safety of oftan-dipivefrin (Sante, Finland) and glaucon (Alcon, USA) are compared in a controlled balanced randomized open parallel study preceded by a period for discharge of the previous drugs. The period of discharge was 7 days, active treatment was administered for 8 weeks. Sixty patients aged 61-69 years were treated. Thirty-one patients were treated by oftan-dipivefrin (group 1) and 29 by glaucon (group 2). In parallel with this, a 1% pilocarpin solution was administered in both groups. The examinations carried out during all consultations included measurements of intraocular pressure before instillations every day at the same time, evaluation of visual acuity, tonography, and study of the central and peripheral visual fields. The time course of hypotensive effects of both drugs showed a sufficient decrease in intraocular pressure in both groups; the effect of oftan-dipivefrin was more pronounced, while glaucon caused the least number of side effects.

Plateau iris syndrome: changes in angle opening associated with dark, light, and pilocarpine administration

PURPOSE

To report changes in angle configuration associated with dark, light, and pilocarpine administration in plateau iris syndrome.

METHOD

In 10 eyes of 10 patients with plateau iris syndrome and persistent narrow angles after patent peripheral Nd:YAG laser iridotomy, ultrasound biomicroscopy was used to image variations in angle opening, iris thickness, and trabecular-ciliary process distance. Measurements were taken in the dark, in full room light, and after administration of pilocarpine 2%.

RESULTS

Average angle opening distance increased in the light compared with the dark (113+/-34 microm vs. 22+/-34 microm, P = .0001) and increased further after pilocarpine administration (171+/-52 microm vs. 113+/-34 microm, P = .0034). Average iris thickness decreased in the light compared with the dark (338+/-34 microm vs. 436+/-58 microm, P = .0009) and decreased further after pilocarpine administration (253+/-48 microm vs. 338+/-34 microm, P = .0002). Average trabecular meshwork-ciliary process distance measurements were smaller than normal and did not change significantly in the light compared with the dark (481+/-42 microm vs. 464+/-44 microm, P = .4001) or after pilocarpine administration compared with light (451+/-67 microm vs. 481+/-42 microm, P = .1304).

CONCLUSIONS

In plateau iris syndrome, anteriorly located ciliary processes support the peripheral iris. Changes in angle opening in dark and light are solely related to changes in iris thickness. Pilocarpine produces iris thinning and is an effective method of opening the angle. Ultrasound biomicroscopy can be used to perform a darkroom provocative test, which provides information on whether the angle anatomically closes in the dark.

[Influence of postoperative topical application of miotics after cataract extraction on intraocular pressure and the blood-aqueous barrier]

BACKGROUND

In the present study we evaluated the influence of topical miotics on intraocular pressure and the blood-aqueous barrier after uncomplicated phacoemulsification and PC-IOL implantation.

PATIENTS AND METHODS

Fifty-two eyes were randomized into 2 groups: with miotics (n = 28) and without miotics (n = 24). The IOP was measured before, 6 h, 1 and 2 days after surgery. Measurement of aqueous flare was performed before and on days 1 and 2 after surgery. Patients with glaucoma, PEX or previous intraocular surgery were excluded.

RESULTS

In the group without miotics the IOP was 17.9 mm Hg (+/- 3.34) 6 h postoperatively; in the second group it was 15.5 mm Hg (+/- 3.25); P = 0.04. On the first postoperative day the IOP measured in the group without miotics was 15.3 mm Hg (+/- 2.70) and with miotics 13.0 mm Hg (+/- 2. 28); P = 0.007. On the second day in the group without miotics the IOP was 13.9 mm Hg (+/- 3.05) and with miotics 12.60 mm Hg (+/- 2. 19); P = 0.53. The changes in aqueous flare on the first and second day after surgery showed no significant influence of miotics on the blood-aqueous barrier (P > 0.05).

CONCLUSIONS

Immediate postoperative application of topical miotics led to a small yet significant reduction of the IOP during the first 24 h after surgery. Our data suggest that there is no need for pharmacological reduction of the IOP after uncomplicated cataract surgery.

Evaluation of pilocarpine loaded gelatin particles for topical ophthalmic use

Gelatin particles containing pilocarpine HCl were prepared using a desolvation method. The influence of the gelatin type and the preparation pH on particle properties was studied. The drug entrapment amounted 44 to 57%, zetapotential was slightly negative. Particle size varied from 312 nm to 500 nm depending on preparation pH. Franz diffusion cell experiments showed a release approaching zero-order kinetics and a sustained release compared to an aqueous pilocarpine HCl solution.

Studies on the effect of pilocarpine incorporation into a submicron emulsion on the stability of the drug and the vehicle

In order to obtain a novel ocular formulation with a potential for prolonging pilocarpine activity, the drug (2.0%) was incorporated into a submicron emulsion containing soya-bean oil and lecithin as emulgator. The effect of drug incorporation into the emulsion on its physical stability and on the other hand, the potential of the vehicle to reduce drug degradation at pH higher than 5.0 was studied. The pH was adjusted to 6.5 or 5.0 and the physicochemical stability of the formulations was observed. The mean diameter of oily particles in the resulting emulsions measured by a laser diffractometer was 0.6-0.7 micron and this was larger than in a drug-free emulsion where a 0.33 micron value was measured. The formulations were physically stable for 6 months at 4 degrees C, but progressing chemical degradation of pilocarpine was noted at pH 6.5. At that pH nearly 8% of pilocarpine was degraded to isopilocarpine and pilocarpic acid, both in the emulsion and in the solution. Thus, it may be concluded that pilocarpine in submicron emulsion is not protected against degradation. The presence of pilocarpine changes the physical stability of the vehicle since the formulation was easily destabilized during autoclaving or at room temperature. In the presence of higher concentration of lecithin (2.4%) or co-emulgators (poloxamer 2.0% or Tween 80 0.5%) the mean droplet size in the emulsions was the same as in a drug-free system. However the emulsions containing poloxamer were not stable during storage. Viscosity of pilocarpine emulsions can be increased by addition of methylcellulose or sodium carmellose (1.0%), but an intensive creaming occurs in these systems. Pilocarpine base is less suitable for emulsion preparation than hydrochloride salt, and emulsions prepared at pH 5.0 show the most satisfying stability.

Clinical use of a topical carbonic anhydrase inhibitor in patients affected by chronic simple glaucoma

The aim of this study is to evaluate the ocular hypotensive efficacy of a topical carbonic anhydrase inhibitor (dorzolamide) in primary open-angle glaucoma patients, administered alone or in association with beta-blockers or with beta-blockers and miotics, in a one-year follow-up.

Effects of dipivefrin and pilocarpine on pupil diameter, automated perimetry and LogMAR acuity

BACKGROUND

A study was carried out to ascertain, in ophthalmologically normal subjects, the short-term effects of dipivefrin hydrochloride 0.1% on visual performance and make comparisons with pilocarpine.

METHODS

Twelve normal volunteers aged 20-26 years attended on three occasions. One eye, randomly selected, received one drop of either pilocarpine 2%, dipivefrin or saline 0.9%. High- and low-contrast LogMAR acuity at 6 m and pupil diameter (measured by infra-red pupillometry) were recorded at baseline (T0) and at intervals up to 90 min following instillation of drops. Program 30-2 of the Humphrey Visual Field Analyzer (HFA) was run at T0 and at 60 min after treatment instillation (T60). Saline was always instilled at visit 1, to allow for learning effects. On visits 2 and 3 either pilocarpine or dipivefrin was randomly instilled into the treated eye.

RESULTS

Pilocarpine significantly worsened the field global indices mean deviation (P < 0.001) and pattern standard deviation (P < 0.01) compared with T0. There was no significant change with dipivefrin. A significant (P = 0.01) pupil dilation from 5.44 mm (SD 0.79) at T0 to 6.19 mm (SD 1.09) at T90 occurred with dipivefrin. Pilocarpine caused significant miosis. No significant changes in LogMAR values were found with dipivefrin. Pilocarpine significantly (P < 0.01) increased LogMAR values (i.e. reduced acuity) compared with dipivefrin. At T30 the mean increase in LogMAR was 0.76 (SD 0.30) for high and 0.83 (SD 0.11) for low contrast. By T90 recovery of acuity was virtually complete.

CONCLUSIONS

In normals dipivefrin causes mydriasis but does not affect the central visual field global indices (as assessed by STATPAC), or high- and low-contrast LogMAR acuity. Pilocarpine adversely affects the visual field and both measures of acuity. Knowledge of these effects is of value in glaucoma therapy and when monitoring the progression of visual loss.

Intraocular pressure-lowering effects of latanoprost monotherapy versus latanoprost or pilocarpine in combination with timolol: a randomized, observer-masked multicenter study in patients with open-angle glaucoma. Italian Latanoprost Study Group

PURPOSE

To compare intraocular pressure (IOP) after adding either latanoprost or pilocarpine to timolol treatment or switching to latanoprost monotherapy in glaucomatous eyes in which IOP was inadequately controlled with timolol.

METHODS

This 6-month randomized study comprised 148 patients with primary open-angle or pseudoexfoliation glaucoma, which was inadequately controlled with topical beta-adrenergic antagonists. After a 2- to 4-week run-in period with timolol 0.5% twice daily, patients were assigned in randomized fashion to three study groups: one group received add-on therapy of latanoprost 0.005% once daily, the second group received add-on therapy of pilocarpine 2% three times daily, and the third group switched to latanoprost 0.005% once daily. Mean diurnal IOP was measured at baseline and after 3 and 6 months of treatment.

RESULTS

At 6 months, 128 patients had completed the study. Diurnal IOP was significantly reduced from baseline in all groups. Adding latanoprost to timolol treatment reduced diurnal IOP by 6.1+/-0.3 mmHg (-28%), adding pilocarpine to timolol treatment reduced diurnal IOP by 4.2+/-0.3 mmHg (-19%), and switching from timolol to latanoprost monotherapy reduced diurnal IOP by 5.5+/-0.3 mmHg (-25%).

CONCLUSION

A significantly greater reduction in diurnal IOP was achieved after addition of latanoprost than after addition of pilocarpine in patients in whom IOP was not adequately controlled with timolol alone. Further, the results of this study indicate that a switch to latanoprost monotherapy can be attempted before combination treatment is initiated.

[An orthogonal model of operative adjustment control of intraocular pressure parameters]

This paper presents the algorithm developed by the authors for operative adjustment of parameters of an orthogonal model of intraocular pressure control.

Effect of intracameral administration of carbachol on the postoperative increase in intraocular pressure in dogs undergoing cataract extraction

OBJECTIVE

To determine whether intracameral injection of carbachol at the completion of phacoemulsification in dogs would prevent the increase in intraocular pressure (i.o.p) that can develop during the first 24 hours after surgery.

DESIGN

Randomized controlled trial.

ANIMALS

32 adult dogs undergoing elective unilateral or bilateral phacoemulsification.

PROCEDURE

Dogs were randomly assigned to 1 of 4 groups with 8 dogs/group: phacoemulsification and intracameral administration of 0.5 ml of 0.01% carbachol at the end of surgery; phacoemulsification, intraocular lens implantation, and intracameral administration of 0.5 ml of 0.01% carbachol; phacoemulsification and intracameral administration of 0.5 ml of balanced salt solution; and phacoemulsification, intraocular lens implantation, and intracameral administration of 0.5 ml of balanced salt solution. Intraocular pressure was measured at 3 and 6 hours and the morning after surgery. Aqueous flare was also measured 6 hours and the morning after surgery.

RESULTS

None of the dogs treated with carbachol developed postoperative ocular hypertension (i.e., IOP > 27 mm of Hg), whereas 12 of 16 control dogs had ocular hypertension 3 hours after surgery. Intraocular pressure 3 hours after surgery was not significantly associated with phacoemulsification time or phacoemulsification power or with whether the dog received an intraocular lens implant. Severity of aqueous flare was similar for treated and control dogs.

CLINICAL IMPLICATIONS

Results suggested that intracameral administration of 0.01% carbachol at the end of surgery was a safe and efficacious method of preventing the postoperative increase in IOP associated with phacoemulsification in dogs.