The role of hyaluronan as a drug carrier to enhance the bioavailability of extended release ophthalmic formulations. Hyaluronan-timolol ionic complexes as a model case.

The aim of this work was to obtain information concerning the properties of ophthalmic formulations based on hyaluronic-drug ionic complexes, to identify the factors that determine the onset, intensity and duration of the pharmacotherapeutic effect. Dispersions of a complex of 0.5% w/v of sodium hyaluronate (HyNa) loaded with 0.5% w/v of timolol maleate (TM) were obtained and presented a counterionic condensation higher than 75%. For comparison a similar complex obtained with hyaluronic acid (HyH) was also prepared. Although the viscosity of HyNa-TM was significantly higher than that of HyH-TM, in vitro release of TM from both complexes showed a similar extended drug release profile (20-31% over 5h) controlled by diffusion and ionic exchange. Ocular pharmacokinetic study performed in normotensive rabbits showed that HyNa-TM complex exhibited attractive bioavailability properties in the aqueous humor (AUC and Cmax significantly higher and later Tmax) compared to commercial TM eye-drops. Moreover, a more prolonged period of lowered intra-ocular pressure (10h) and a more intense hypotensive activity was observed after instillation of a drop of HyNa-TM as compared to the eye-drops. Such behavior was related to the longer pre-corneal residence times (400%) observed with HyNa-TM complex. No significant changes in rabbit transcorneal permeation were detected upon complexation. These results demonstrate that the ability of HyNa to modulate TM release, together with its mucoadhesiveness related to the viscosity, affected both the pharmacokinetic and pharmacodynamic parameters. The HyNa-TM complex is a potentially useful carrier for ocular drug delivery, which could improve the TM efficacy and reduce the frequency of administration to improve patient compliance.

RP-HPLC method development for the simultaneous determination of timolol maleate and human serum albumin in albumin nanoparticles.

An isocratic high-performance liquid chromatographic method was developed and validated for the simultaneous determination of human serum albumin (HSA) and timolol in albumin nanoparticles. This method involved a reversed-phase-C18 column thermostated at 25 °C, UV detection at 276 nm, flow rate of 1.0 ml/min and a mobile phase compounded by 0.05% (v/v) trifluoroacetic acid in water/0.05% (v/v) trifluoroacetic acid in an acetonitrile (40:60, v/v) solution. The elution times for albumin and timolol were 1.84 ± 0.05 min and 2.67 ± 0.04 min, respectively. Calibration curves were linear from 0.2 to 100 mg/ml for HSA and 0.01 to 1 mg/ml for timolol. Limits of quantification were 0.2 mg/ml for HSA and 0.01 mg/ml for timolol. The values of accuracy and precision of intra- and inter-day variation studies were within acceptable limits, according to the US Food and Drug Administration Guidance for Industry. The described method has proved to be useful to give accurate measurements of human serum albumin and timolol from albumin nanoparticles to determine the percentage of encapsulation and the process yield.

Novel bioadhesive hyaluronan-itaconic acid crosslinked films for ocular therapy.

New hyaluronic acid (HA)-itaconic acid (IT) films have been previously synthesized and used as potential topical drug delivery systems (DDS) for ocular administration. In this study we explored homogeneous and heterogeneous crosslinking reactions of HA using glutaraldehyde (GTA) and polyethylene glycol diglycidyl ether (PEGDE) in the presence of IT, a naturally occurring compound that is non-toxic and readily biodegradable. We have studied the morphology, mechanical properties and in vitro biocompatibility between these new materials and ocular surface cells (human corneal epithelial cell line) and evaluated the biopharmaceutical performance of the designed formulations. Although all the synthesized materials exhibited good mechanical properties, the PEGDE modified films exhibited the best biocompatibility, with in vivo assays showing good adhesive performance and minimal irritation. PEGDE films were also tested for their effects in the treatment of intraocular pressure (IOP) in rabbits using timolol maleate (TM) as the model drug. These results may be useful for further design of novel bioadhesive matrix containing drugs by topical application in ophthalmology.

Chemometric determination of amiloride hydrochloride, atenolol, hydrochlorothiazide and timolol maleate in synthetic mixtures and pharmaceutical formulations.

Different chemometric methods such as classical least squares (CLS), principal components regression (PCR) and partial least squares with one dependent variable (PLS-1) applied on UV spectral data (0 D) and on their first derivatives (1 D) were evaluated for the simultaneous quantification of samples containing mixtures of amiloride hydrochloride, atenolol, hydrochlorothiazide and timolol maleate. Their performances were compared by means of ANOVA tests, which evidenced that 0 D-PCR, 0D-PLS-1, 1D-PCR, 1D-PLS-1, were reproducible and gave statistically similar results, while 0 D-CLS and 1D-CLS displayed higher variances than the former and failed to comply with the Levene's variance homogeneity test at different stages of the method comparison and validation process. The four statistically equivalent procedures were successfully applied to the analysis of synthetic samples with two to four analytes and to commercial tablet preparations containing amiloride hydrochloride and hydrochlorothiazide alone or in association with atenolol or timolol maleate.

[Physiologic significance of the interaction between timolol and free amino acids in eye structures]. / Fyziologický význam interakcie timololu s volnými amínokyselinami v struktúrach oka.

The authors analyze the interaction of timolol maleate (Timoptol, Léciva Prague) with free amino acids with regard to the effect on intraocular pressure. The different colour reaction of an amino acid mixture with Timoptol, the decline of radioactivity of Na[I125] tyrosine with Timoptol and the formation of 8 radioactive fractions after addition of Timoptol to Na[I125] indicate: a) the specificity of interaction of each amino acid with Timoptol; b) suggest that between Timoptol and free amino acids a firm covalent bond develops with the concurrent development of a new biologically active metabolite. Evidence of the presence of a new metabolite is important from the aspect of understanding and more accurate definition of the action of Timoptol in tissue structures of the eye and thus also for possible effective treatment of glaucoma.

Singlet molecular oxygen generation and quenching by the antiglaucoma ophthalmic drugs, Timolol and Pindolol.

The dye sensitized photooxidation in water (pH 6), of the pharmaceutical topical antiglaucoma drugs, Timolol and Pindolol, which act as beta-adrenergic receptor antagonists, were studied by means of static and time-resolved spectroscopic methods and polarographic determinations. O2(1delta(g))-mediated photooxidation of Timolol and Pindolol takes place with quantum efficiencies of 0.035 and 0.16, respectively, which raises concern about the possible daylight-mediated photodamaging of the drugs, in the presence of sensitizing agents. Pindolol behaves kinetically as a typical indole derivative, for which the intermediacy of a polar complex is proposed. Solvent effects on the kinetics of photooxidation suggests that the same mechanism could operate for the case of Timolol. Upon direct ultraviolet-light irradiation Timolol and Pindolol generate O2(1delta(g)), with quantum yields of 0.027 and 0.11 respectively. The former comprises three desirable properties for an external-use ocular drug: a reduced efficiency of O2(1delta(g)) photooxidation, a relatively high power as O2(1delta(g)) physical deactivator and a relatively low propensity to O2(1delta(g)) generation upon direct light irradiation.

Stability of pilocarpine ophthalmic solutions.

The stability of pilocarpine and pilocarpine-timolol eyedrop preparations available on the Argentine market was studied. A high-performance liquid chromatographic method that allows the estimation of pilocarpine in the presence of degradation products was used for the study according to the preestablished design. It was found that pilocarpine solutions are stable, while pilocarpine in association with timolol shows significant degradation.

Profilaxia eficaz da hipertensäo pós YAG-laser para capsulotomia posterior / Efficient probhylaxy of ocular hypertension after YAG laser capsulotomy

Objetivou-se testar a eficácia da acetozolamida timoral e opraclonidine na prevençäo da eventual hipertensäo pós-YAG Laser para capsulotomia posterior, em pacientes näo glaucomatosos. Vinte e três pacientes (24 olhos) incluídos foram divididos em dois grupos 8 A e B. Näo houve diferença significativa (p>0.1) entre os grupos para sexo, média de idade, média de pressäo ocular (Po) inicial (A=11,5ñ4mmHg e B=13ñ4,4mmHg), assim como média de energia total do Laser (quantidade de energia de cada disparo multiplicada pelo número de disparos) utilizada em cada paciente (A=94,7ñ65,3mj e B=82,3ñ68,3mj). O grupo A recebeu 500mg de acetazolamida via oral (VO)1 hora antes do Laser, mais uma gota de timolol 05 (por cento) 1 horaa antes e outra logo após. Ao grupo B acrescentou-se 1 gota de apraclodine 1 (por cento) 1 hora anttes e outra logo após. FOram realizadas aferiçöes 1 hora antes, 2, 3, 24 horas e uma semana depois. Nenhum dos grupos apresentou aumento médio maior do que 1mmHg, em nehuma das aferiçöes, e a diferença entre eles näo foi significativa (p>0,1). A energia total do Laser usada em cada paciente näo mostrou correlaçäo com a o (r=192 e p=3687,no horário de aparente maior correlaçäo (24h). Os autores concluem pela eficácia do método. Ponderam, entretanto, sobre a segurança em se adotar uma rotina menos agressiva, baseados nos próprios resultados e na literatura pesquisada. Sugerem 125 a 250mg de acetazolamida VO 1 hora antes, acrescentando-se somente uma droga tópica.