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Couți N, Porfire A, Iovanov R, Crișan AG, Iurian S, Casian T, Tomuță I. Polyvinyl Alcohol, a Versatile Excipient for Pharmaceutical 3D Printing. Polymers (Basel) 2024; 16:517. [PMID: 38399895 PMCID: PMC10893462 DOI: 10.3390/polym16040517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 02/02/2024] [Accepted: 02/09/2024] [Indexed: 02/25/2024] Open
Abstract
Three-dimensional (3D) printing in the pharmaceutical field allows rapid manufacturing of a diverse range of pharmaceutical dosage forms, including personalized items. The application of this technology in dosage form manufacturing requires the judicious selection of excipients because the selected materials must be appropriate to the working principle of each technique. Most techniques rely on the use of polymers as the main material. Among the pharmaceutically approved polymers, polyvinyl alcohol (PVA) is one of the most used, especially for fused deposition modeling (FDM) technology. This review summarizes the physical and chemical properties of pharmaceutical-grade PVA and its applications in the manufacturing of dosage forms, with a particular focus on those fabricated through FDM. The work provides evidence on the diversity of dosage forms created using this polymer, highlighting how formulation and processing difficulties may be overcome to get the dosage forms with a suitable design and release profile.
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Affiliation(s)
| | - Alina Porfire
- Department of Pharmaceutical Technology and Biopharmacy, Faculty of Pharmacy, University of Medicine and Pharmacy “Iuliu Hatieganu”, 400012 Cluj-Napoca, Romania; (N.C.); (R.I.); (A.G.C.); (S.I.); (T.C.); (I.T.)
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Oucif A, Haddadine N, Zakia D, Bouslah N, Benaboura A, Beyaz K, Guedouar B, El-Shall MS. Poly (hydroxyethyl methacrylate-co-hydroxyethyl acrylate) soft contact lenses for acetazolamide release. Polym Bull (Berl) 2021. [DOI: 10.1007/s00289-021-03573-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Dumitriu S, Popa M, Vancea P, Costin D. Polycomponent Ophthalmic Inserts with Polysaccharide Support. J BIOACT COMPAT POL 2016. [DOI: 10.1177/088391158800300404] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Ophthalmic inserts, based on xanthane modified with pilocarpine, adrena line and hydrocortisone have been prepared. The drugs were fixed in the insert by ionic bonds and gel entrapment. The in vitro release rate of pilocarpine de pended on the degree of xanthane modification and on the drug content in the polymer matrix. Inserts show a high ophthalmic tolerance indicating the potential for treatment of glaucoma.
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Affiliation(s)
- Severian Dumitriu
- Polytechnic Institute of Jassy Department of Organic and Macromolecular Chemistry 23 August 11, R-6600, Jassy, Romania
| | - Marcel Popa
- Polytechnic Institute of Jassy Department of Organic and Macromolecular Chemistry 23 August 11, R-6600, Jassy, Romania
| | - Petre Vancea
- Institute of Medicine and Pharmacy Universitatii 15 R-6600, Jassy, Romania
| | - Danut Costin
- Institute of Medicine and Pharmacy Universitatii 15 R-6600, Jassy, Romania
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Saettone MF, Alderigi C, Giannaccini B, Galli-angeli D. Preparation and Evaluation of A Sustained-Release Ophthalmic Vehicle for Dapiprazole. Drug Dev Ind Pharm 2008. [DOI: 10.3109/03639048909052550] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Alvarez-Lorenzo C, Hiratani H, Gómez-Amoza JL, Martínez-Pacheco R, Souto C, Concheiro A. Soft contact lenses capable of sustained delivery of timolol. J Pharm Sci 2002; 91:2182-92. [PMID: 12226845 DOI: 10.1002/jps.10209] [Citation(s) in RCA: 174] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The aim of this work was to evaluate the influence of the composition and the application of an imprinting technique on the loading capability of weakly crosslinked hydroxyethyl methacrylate (HEMA) hydrogels, with a view to their use as reloadable soft contact lenses for administration of timolol. Hydrogels were prepared by dissolution of ethylene glycol dimethacrylate (EGDMA, 10 mM) in HEMA with or without methacrylic acid (MAA) or methyl methacrylate (MMA; 100-400 mM) and with or without timolol maleate (10 mg/mL), initiation of polymerization by addition of 2,2'-azo-bis(isobutyronitrile) (AIBN, 10 mM), injection in molds, and curing in an oven at 50-70 degrees C. Unreacted reagents were removed by boiling. The dry hydrogels were clear and fully polymerized with smooth, poreless surfaces and presented optimal mechanical properties. The hydrogels were then characterized by determination of their swelling and timolol release kinetics in 0.9% NaCl, phosphate buffer (pH 7.4) and artificial lacrimal fluid, and of the timolol loading capacity of both nonimprinted hydrogels and de-timololized imprinted hydrogels at various pHs. Both water uptake and timolol release exhibited Fickian kinetics, except in the case of hydrogels made with 400 mM MAA. Timolol diffusion into 0.9% NaCl from HEMA or HEMA/MMA was slow; release from HEMA/MAA into phosphate buffer or lacrimal fluid was faster and increased with the MAA content of the polymer. Timolol loading was significant for HEMA/MAA hydrogels (imprinted or not) at pH 5.5-7.5, and specially for imprinted hydrogels containing 100 mM MAA, which absorb 12 mg timolol/g dry hydrogel. The results indicate that the incorporation of MAA as comonomer increases the timolol loading capacity to therapeutically useful levels while retaining appropriate release characteristics.
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Affiliation(s)
- Carmen Alvarez-Lorenzo
- Departamento de Farmacia y Tecnología Farmacéutica, Facultad de Farmacia, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain.
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Kawakami S, Nishida K, Mukai T, Yamamura K, Nakamura J, Sakaeda T, Nakashima M, Sasaki H. Controlled release and ocular absorption of tilisolol utilizing ophthalmic insert-incorporated lipophilic prodrugs. J Control Release 2001; 76:255-63. [PMID: 11578740 DOI: 10.1016/s0168-3659(01)00441-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
To control ocular drug delivery, the O-butyryl ester prodrug of tilisolol (BUTL) and the O-palmitoyl ester prodrug of tilisolol (PalTL) were incorporated into an ophthalmic insert. The released TL from BUTL inserts and PalTL inserts in pH 7.4 phosphate-buffered saline until 5 h were approximately 25% and 3% of that from TL inserts, respectively. In addition, BUTL was also released from BUTL inserts. However, PalTL was not released from the PalTL insert. The release of drugs from TL inserts and BUTL inserts was little affected by the addition of bovine serum albumin (BSA) in pH 7.4 phosphate-buffered saline. In contrast, the release of drugs from PalTL inserts were enhanced by the addition of BSA. After application of TL, BUTL, and PalTL inserts to the rabbit eye, the aqueous humor concentration of TL was prolonged compared with TL instillation, and the plasma concentration of TL was much lower than that of TL instillation. The ratios of the area under the TL concentration-time curve (AUC) in the aqueous humor to AUC in the plasma (AUC(aqueous)/AUC(plasma)) after application of BUTL until 8 h were 3.1-fold and 3.8-fold higher than those of the TL insert and PalTL insert, respectively.
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Affiliation(s)
- S Kawakami
- School of Pharmaceutical Sciences, Nagasaki University, 1-14 Bunkyo-machi, 852-8521, Nagasaki, Japan.
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Shedden A, Laurence J, Tipping R. 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. Clin Ther 2001; 23:440-50. [PMID: 11318078 DOI: 10.1016/s0149-2918(01)80048-5] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
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.
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Affiliation(s)
- A Shedden
- Department of Ophthalmic Clinical Research, Merck Research Laboratories, West Point, Pennsylvania, USA
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Rosenlund EF. The intraocular pressure lowering effect of timolol in gel-forming solution. ACTA OPHTHALMOLOGICA SCANDINAVICA 1996; 74:160-2. [PMID: 8739682 DOI: 10.1111/j.1600-0420.1996.tb00062.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The effect on the intraocular pressure (IOP) of 0.5% timolol solution given twice daily was compared to 0.5% timolol in gel-forming solution given once daily. Patients (n = 223) having an IOP of above 22 mmHg were recruited from 16 eye specialist centres in Scandinavia and Finland. The patients were randomized to two treatment groups, timolol solution treatment and timolol in gel-forming solution treatment. Eyes with and without pseudoexfoliation were included. The patients were stratified regarding the presence or not of pseudoexfoliation, to ensure appropriate distribution of this condition. No difference in intraocular pressure reducing effect was registered for the two groups. The pressure reducing effect of the two modes of treatment was not affected by the presence or not of pseudoexfoliation. The study also included registration of local and systemic signs and symptoms possibly related to the study medications. Blurring of vision occurred more often in patients given 0.5% timolol in gel-forming solution compared to timolol solution. The heart rate decreased statistically significantly in patients given timolol solution, but not in patients given timolol in gel-forming solution. This study suggests that treatment with 0.5% timolol in gel-forming solution once a day may be equally as good as 0.5% timolol solution given twice a day in patients with glaucoma both with and without pseudoexfoliation.
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Sasaki H, Yamamura K, Nishida K, Nakamura J, Ichikawa M. Delivery of drugs to the eye by topical application. Prog Retin Eye Res 1996. [DOI: 10.1016/1350-9462(96)00014-6] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Evaluation of pilocarpine-loaded albumin particles as controlled drug delivery systems for the eye. II. Co-administration with bioadhesive and viscous polymers. J Control Release 1995. [DOI: 10.1016/0168-3659(94)00059-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Drug release from an ophthalmic insert of a beta-blocker as an ocular drug delivery system. J Control Release 1993. [DOI: 10.1016/0168-3659(93)90216-r] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Saettone M, Torracca M, Pagano A, Giannaccini B, Rodriguez L, Cini M. Controlled release of pilocarpine from coated polymeric ophthalmic inserts prepared by extrusion. Int J Pharm 1992. [DOI: 10.1016/0378-5173(92)90193-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Järvinen T, Suhonen P, Naumanen H, Urtti A, Peura P. Determination of physicochemical properties, stability in aqueous solutions and serum hydrolysis of pilocarpic acid diesters. J Pharm Biomed Anal 1991; 9:737-45. [PMID: 1821151 DOI: 10.1016/0731-7085(91)80215-u] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
New alkyl and aralkyl pilocarpic acid diesters, prodrugs of pilocarpine, were synthesized with the aim of improving the bioavailability of pilocarpine by increasing its corneal permeability. These esters were several orders of magnitude more lipophilic than pilocarpine as determined by their apparent partition coefficients between 1-octanol and phosphate buffer (pH 7.40) (log P). Good correlation between log P and HPLC capacity factors of the compounds was observed. All the compounds are stable in acidic aqueous solution; in serum, however, pilocarpic acid diesters are hydrolysed enzymatically to pilocarpic acid monoester, which undergoes spontaneous cyclization to active pilocarpine and inactive isopilocarpine. The half-lives of the diesters in serum varied from 6-232 min. In addition to the direct effects of the R2, R1 moiety had a remarkable effect on the rate of enzyme-catalysed hydrolysis taking place in moiety R2. The formed pilocarpine was analysed with a new HPLC method which allowed good resolution of pilocarpine, isopilocarpine, pilocarpic acid and isopilocarpic acid. Rates for pilocarpine formation were both determined by experiment and calculated using the STELLA simulation programme with known degradation rate constants of pilocarpic acid diesters and monoesters. Since the simulations were in good agreement with the experimental results, it is concluded that STELLA simulation programme is useful in predicting pilocarpine formation.
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Affiliation(s)
- T Järvinen
- Department of Pharmaceutical Chemistry, University of Kuopio, Finland
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Dumortier G, Zuber M, Chast F, Sandouk P, Chaumeil J. Systemic absorption of morphine after ocular administration: evaluation of morphine salt insert in vitro and in vivo. Int J Pharm 1990. [DOI: 10.1016/0378-5173(90)90058-c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Cheeks L, Green K, Stone RP, Riedhammer T. Comparative effects of pilocarpine in different vehicles on pupil diameter in albino rabbits and squirrel monkeys. Curr Eye Res 1989; 8:1251-8. [PMID: 2627795 DOI: 10.3109/02713688909013904] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Several commercial pilocarpine preparations have been compared for their efficacy of drug delivery as evaluated by changes in pupil diameter, and return to base-line pupil size, in rabbits and squirrel monkeys. Adsorbocarpine, Isoptocarpine, Pilocar, all at 2%, and Pilopine HS gel, 4%, were used. In albino rabbits the order of efficacy, as judged by area under the curve, or maximal pupil diameter change, was Pilopine greater than Isoptocarpine = Adsorbocarpine greater than Pilocar = saline (prepared in this laboratory). In general, greater areas under the curve were associated with greater changes in pupil diameter. Pupil diameter had returned to normal by a maximum of 5 hours after drop instillation. In squirrel monkeys, the maximum pupillary change was statistically (P greater than 0.05) the same for all preparations, as was the percentage change in pupil diameter at 6 hours since pupils were still somewhat constricted at this time after drop instillation. The differences in area under the curve were minor. The greater response in primates compared to rabbits may be due to differences in pigment, intraocular kinetics and a far more active ciliary muscle in primates. Also studied were newly developed, non-surfactant containing, preservative-free polymer- and microparticle-based vehicles. Some of the vehicles, based on cyanoacrylate, modified hyaluronate, anionic copolymers, polyvinyl-pyrrolidone, cross-linked gelatin and microparticles showed greater pupillary changes and areas under the curve in rabbits compared to saline vehicle. When compared to commercial preparations in the monkey eye cyanoacrylate block copolymer and modified hyaluronate showed an increase in efficacy. Polyvinylpyrrolidone, anionic copolymer and cross-linked gelatin were equal to the commercial preparations.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L Cheeks
- Department of Ophthalmology, Medical College of Georgia, Augusta
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Abstract
The bioavailability of drugs from conventional ophthalmic formulations is low. To optimize the therapy, sustained release ophthalmic dosage forms are warranted. Hydrogels such as sodium-carboxymethyl cellulose, hydroxypropylmethyl cellulose, Carbopol-940, Carbopol-941 and Lutrol-FC-127 increase the duration of action of various drugs. Gels containing pilocarpine were prepared and evaluated by measuring the intensity and duration of miotic response in albino rabbits. Carbopol-940 gels, being the best of those used, were studied further for the effect of its concentration and of additives (benzalkonium chloride, phenylmercuric nitrate, chlorbutol and disodium edetate), autoclaving at 121 degrees C for 30 min and irradiation with gamma rays (2.5 Mrad), on the end product.
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Affiliation(s)
- S G Deshpande
- Department of Chemical Technology, University of Bombay, India
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Kassem M, Attia M, Habib F, Mohamed A. Activity of ophthalmic gels of betamethasone and phenylephrine hydrochloride in the rabbit's eye. Int J Pharm 1986. [DOI: 10.1016/0378-5173(86)90097-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Lee VH, Robinson JR. Topical ocular drug delivery: recent developments and future challenges. JOURNAL OF OCULAR PHARMACOLOGY 1986; 2:67-108. [PMID: 3332284 DOI: 10.1089/jop.1986.2.67] [Citation(s) in RCA: 358] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Existing ocular drug delivery systems are fairly primitive and inefficient, but the stage is set for the rational design of newer and significantly improved systems. The focus of this review is on recent developments in topical ocular drug delivery systems relative to their success in overcoming the constraints imposed by the eye and to the improvements that have yet to be made. In addition, this review attempts to place in perspective the importance of pharmacokinetic modeling, ocular drug pharmacokinetic and bioavailability studies, and choice of animal models in the design and evaluation of these delivery systems. Five future challenges are perceived to confront the field. These are: (a) The extent to which the protective mechanisms of the eye can be safely altered to facilitate drug absorption, (b) Delivery of drugs to the posterior portion of the eye from topical dosing, (c) Topical delivery of macromolecular drugs including those derived from biotechnology, (d) Improved technology which will permit non-invasive monitoring of ocular drug movement, and (e) Predictive animal models in all phases of ocular drug evaluation.
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Affiliation(s)
- V H Lee
- University of Southern California, School of Pharmacy, Los Angeles
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Vidmar V, Pepeljnjak S, Jalsenjak I. The in vivo evaluation of poly(lactic acid) microcapsules of pilocarpine hydrochloride. J Microencapsul 1985; 2:289-92. [PMID: 3880490 DOI: 10.3109/02652048509033840] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Poly(lactic acid) microcapsules of pilocarpine hydrochloride were prepared and evaluated by measuring a miotic effect in rabbits. The microcapsule suspension showed prolongation of miosis and an improved bioavailability when compared with a standard eye dosage form.
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Affiliation(s)
- V Vidmar
- Faculty of Pharmacy and Biochemistry, University of Zagreb, Croatia, Yugoslavia
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Urtti A, Juslin M, Miinalainen O. Pilocarpine release from hydroxypropyl-cellulose-polyvinylpyrrolidone matrices. Int J Pharm 1985. [DOI: 10.1016/0378-5173(85)90090-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Lee VH, Urrea PT, Smith RE, Schanzlin DJ. Ocular drug bioavailability from topically applied liposomes. Surv Ophthalmol 1985; 29:335-48. [PMID: 3992472 DOI: 10.1016/0039-6257(85)90109-2] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
During the past decade liposomes have been investigated extensively for their ability to improve drug utilization by the body, first in the area of chemotherapeutics and most recently in the area of ophthalmology. Liposomes are vesicle-like structures with a concentric series of alternating compartments of aqueous spaces and phospholipid bilayers. To date, liposomes have been found to both promote and reduce ocular drug absorption, indicating that a definite need exists for further studies to evaluate the interplay of drug, liposomes, and the corneal surface in determining the effectiveness of liposomes as vehicles for topically applied ophthalmic drugs. The purpose of this review is to place in perspective the role of liposomes in topical ocular drug delivery. As background material, the factors influencing ocular drug bioavailability and the features of liposomes pertinent to their effectiveness as drug carriers are reviewed.
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