Preparation and evaluation of HPMC-based pirfenidone solution in vivo.

CONTEXT: Pirfenidone (PFD) has exhibited therapeutic potential in the treatment of cell proliferative disorders. The previously developed 0.5% water-based PFD eye drops by our team exhibited antiscarring effectiveness and ocular safety but with a limit of short half-life and poor bioavailability. OBJECTIVE: To increase bioavailability of the water-based PFD eye drops, we prepared a viscous solution by adding hydroxypropyl methylcellulose (HPMC, F4M), which acted as a viscosity-enhancer. Subsequently, we compared the HPMC-based PFD solution with the water-based PFD eye drops. MATERIALS AND METHODS: PFD solution with 1% HPMC (w/v) was prepared, and the viscosities at different shear rates were measured to investigate its rheology. PFD concentrations in the tear, aqueous humor, conjunctiva, cornea, and sclerae of New Zealand rabbits were detected at different time points with high-performance liquid chromatography (HPLC) following single instillation of the 0.5% PFD (w/v) water-based eye drops or HPMC-based solution. RESULTS: Compared with the 0.5% water-based PFD eye drops, the HPMC-based solution increased the PFD levels in tears and prolonged the residence time from 10 to more than 20 min (p < .01). Consequently, the concentrations of PFD in aqueous humor, conjunctiva, cornea, and sclera were elevated to varying degrees until 90 min after topical administration. CONCLUSIONS: The developed formulation possesses a same readily administration and simple preparation as the PFD eye drops; however, the HPMC-based solution exhibited the higher bioavailability.

Preparation of 0.05% FK506 suspension eyedrops and its pharmacokinetics after topical ocular administration.

PURPOSE: To investigate the stability of FK506 eye suspension and its pharmacokinetics in rabbit aqueous humor, as well as its distribution in eye tissues. METHODS: Sedimentation rate, flocculation value, redispersion time, rheological study, and accelerated experiment were determined for evaluating the stability of FK506 suspension. In a single-dose pharmacokinetic study, six rabbits were instilled a 25-microL drop of 0.05% FK506 suspension and aqueous humor samples were collected at different intervals after administration. In a multiple-dose pharmacokinetic study, a 25-microL drop of FK506 suspension was instilled into the right eye of six rabbits four times a day for 7 days. On the eighth day, aqueous humor samples were collected before the administration of the first, second, third dose, and at different checkpoints after the third dose. For tissue distribution study, six eyes per time points (18 rabbits in total) were treated with single dose of FK506 suspension, and the eyes were enucleated at 60, 100, and 240 min after treatment, then eye tissues were collected. The concentrations of FK506 in all samples were determined by LC-MS/MS. RESULTS: The preliminary results indicated that the stability of FK506 suspension was in accord with the standards of Chinese pharmacopoeia. The maximum concentrations of aqueous humor after single dose and multiple dose administrations were 31.40 +/- 9.32 ng/mL and 37.73 +/- 11.25 ng/mL, respectively. The concentration of FK506 in cornea at 60, 100, and 240 min after a single dose were 402.0 +/- 96.8 ng/g, 363.8 +/- 84.5 ng/g, and 220 +/- 62.3 ng/g, respectively. Determination of pharmacokinetic parameters of single-dose and multiple-dose administration, as well as the FK506 concentrations in eye tissues, showed that the FK506 formulation and the dosing regimen ensured the therapeutic concentration of FK506 for treating corneal allograft rejection. CONCLUSIONS: Based on the stability, single-dose and multiple-dose pharmacokinetics, and tissue distribution, FK506 suspension eyedrops may be a suitable candidate for clinical application in ophthalmology.

[Ocular penetration and pharmacokinetics of topical voriconazole in rabbit eyes].

OBJECTIVE: To investigate the penetration of topical 1% voriconazole into the cornea and aqueous humor in New Zealand white rabbits. METHODS: It was a experimental study. Forty-eight healthy rabbits were randomly divided into groups A (21 cases), B (21 cases) and C (6 cases). Blank samples from group C were used to determine the essential parameters for the validation of analytical procedures. A single 50 microl drop of 1% voriconazole was administered in group A (non-debrided cornea) and group B (debrided cornea). The aqueous humor and the cornea were obtained at 2, 5, 10, 15, 30, 60 and 90 min after application. All samples were analyzed by high-performance liquid chromatography (HPLC). The HPLC system consisted of Waters 1525 pump, Phenomenex Luna C18 (250.0 mm x 4.6 mm, 5.0 microm) column, Phenomenex C18 (4.0 mm x 3.0 mm, 5.0 microm) analytical steel column and a Waters Empower data workstation. The UV detector was set to 255.0 nm. Methanol-0.04 mol/L ammonium hydroxide (62:38, V/V) was used as mobile phase and the flow rate was 0.8 ml/min. External standard was used in this assay. The pharmacokinetic parameters were calculated with nonlinear least square method by the computer. RESULTS: Calibration curves were linear over the range 0.1-15.0 mg/L. The concentration at 0.1 mg/L was the lowest quantified limit. The recovery of voriconazole from aqueous humor samples ranged from 91.06% to 94.80%, and ranged from 79.84% to 83.20% in the cornea samples. After single dose application, the drug concentration in aqueous humor peaked at 10 min in both group A [ (5.172 +/- 1.012) mg/L] and group B [(6.118 +/- 1.123) mg/L], and the parameters t(1/2 ke) in groups A and B were 6.859 min and 13.176 min, respectively. However, peak drug levels were achieved immediately at 2 min in the cornea [group A: (9.958 +/- 3.481) microg/g and group B: (158.476 +/- 10.462) microg/g]. The parameter t(1/2 beta) in nondebrided cornea was 94.938 min and 46.367 min in debrided corneas. CONCLUSIONS: Topical voriconazole exhibits excellent penetration into the cornea, and effective high drug levels are achieved in both the cornea and aqueous humor after single dose application. It can be a prominent agent for the treatment of fungal keratitis in the future.

[The pharmacokinetics of FK506 and its nanoparticles in aqueous humor of rabbits].

OBJECTIVE: To investigate the pharmacokinetics of FK506 and its nanoparticles in aqueous humor of rabbits applied with eye drops or subconjunctiva injections. METHODS: 42 New Zealand albino rabbits were divided into 2 groups. (1) Nanoparticle solution containing 10 microg FK506 was injected into subconjunctiva or dropped on conjunctival sac of rabbits (68 eyes in 34 cases). (2) Eye drops containing 20 or 40 microg FK506 without nanoparticles were dropped on conjunctival sac of rabbits (16 eyes in 8 cases). Aqueous humor was collected at different times after local administration and FK506 concentrations were measured by ELISA. Ocular pharmacokinetic parameters of FK506 were calculated by 3p87 software. RESULTS: In the solution containing nanoparticle, the effective FK506 concentration in aqueous humor could be kept up to 16 h in eye drops group. The range of FK506 concentration was between (15.50 +/- 3.39) - (2.59 +/- 0.83) ng/ml. FK506 in aqueous humor can be maintained for 96 h by injecting into subconjunctiva and FK506 concentration were between (9.62 +/- 2.19) - (2.60 +/- 0.21) ng/ml from 6 - 96 h. T(max) and C(max) in eye drops were (1.25 +/- 0.50) h and (15.52 +/- 2.37) ng/ml respectively; while T(max) and C(max) in subconjunctiva injection were (64.00 +/- 13.86) h and (10.16 +/- 1.37) ng/ml respectively. Each AUC(0-->t) was (152.44 +/- 16.74) ng.ml(-1).h(-1) and (612.48 +/- 54.39) ng.ml(-1).h(-1) respectively; each Ka was 3.790 +/- 0.730 and 0.040 +/- 0.004 respectively; and each MRT was (8.20 +/- 1.28) h and (58.53 +/- 5.42) h respectively. In the eye drops containing 20 microg or 40 microg FK506 but without nanoparticles applied in conjunctival sac of rabbits, all effective FK506 concentrations in aqueous humor could not be kept over 4 h. T(max) was 1 h and C(max) was (18.93 +/- 6.95) ng/ml in 20 microg FK506, while in 40 microg FK506 T(max) was 2h and C(max) was (28.33 +/- 1.31) ng/ml. CONCLUSION: Solution with FK506 nanoparticle dropping onto the eye or injecting into subconjunctiva could be sustained in rabbit aqueous humor for a longer time than non-nanoparticle FK506 solution, while with injecting of nanoparticle FK506 solution it could be detected with a relative low but longer effective concentration.