Process and formulation variables of pregabalin microspheres prepared by w/o/o double emulsion solvent diffusion method and their clinical application by animal modeling studies.

Pregabalin is an anticonvulsant drug used for neuropathic pain and as an adjunct therapy for partial seizures with or without secondary generalization in adults. In conventional therapy recommended dose for pregabalin is 75 mg twice daily or 50 mg three times a day, with maximum dosage of 600 mg/d. To achieve maximum therapeutic effect with a low risk of adverse effects and to reduce often drug dosing, modified release preparations; such as microspheres might be helpful. However, most of the microencapsulation techniques have been used for lipophilic drugs, since hydrophilic drugs like pregabalin, showed low-loading efficiency and rapid dissolution of compounds into the aqueous continous phase. The purpose of this study was to improve loading efficiency of a water-soluble drug and modulate release profiles, and to test the efficiency of the prepared microspheres with the help of animal modeling studies. Pregabalin is a water soluble drug, and it was encapsulated within anionic acrylic resin (Eudragit S 100) microspheres by water in oil in oil (w/o/o) double emulsion solvent diffusion method. Dichloromethane and corn oil were chosen primary and secondary oil phases, respectively. The presence of internal water phase was necessary to form stable emulsion droplets and it accelerated the hardening of microspheres. Tween 80 and Span 80 were used as surfactants to stabilize the water and corn oil phases, respectively. The optimum concentration of Tween 80 was 0.25% (v/v) and Span 80 was 0.02% (v/v). The volume of the continous phase was affected the size of the microspheres. As the volume of the continous phase increased, the size of microspheres decreased. All microsphere formulations were evaluated with the help of in vitro characterization parameters. Microsphere formulations (P1-P5) exhibited entrapment efficiency ranged between 57.00 ± 0.72 and 69.70 ± 0.49%; yield ranged between 80.95 ± 1.21 and 93.05 ± 1.42%; and mean particle size were between 136.09 ± 2.57 and 279.09 ± 1.97 µm. Pregabalin microspheres having better results among all formulations (Table 3) were chosen for further studies such as differential scanning calorimetry, Fourier transform infrared analysis and dissolution studies. In the last step, the best pregabalin microsphere formulation (P3) was chosen for in vivo animal studies. The pregabalin-loaded microspheres (P3) and conventional pregabalin capsules were applied orally in rats for three days, resulted in clinical improvement of cold allodynia, an indicator of peripheral neuropathy. This result when evaluated together with the serum pregabalin levels and in vitro release studies suggests that the pregabalin microspheres prepared with w/o/o double emulsion solvent diffusion method can be an alternative form for neuropathic pain therapy. Conclusively, a drug delivery system successfully developed that showed modified release up to 10 h and could be potentially useful to overcome the frequent dosing problems associated with pregabalin conventional dosage form.

Formulation and evaluation of diclofenac potassium fast-disintegrating tablets and their clinical application in migraine patients.

The aim of this study was to prepare fast-disintegrating tablets (FDTs) of diclofenac potassium with sufficient integrity as well as a pleasant taste, using two different fillers and binders: Tablettose 70(®) and Di-Pac(®). Tablets were made with direct compression method. Tablet properties such as porosity, hardness, and disintegration time were determined. Diclofenac potassium determinations were carried out using a validated spectrophotometric method for the analysis of drug. Furthermore, in vivo experiments were carried out to compare the analgesic effect and the time to relieve migraine headache between the commercial tablets and FDTs of diclofenac potassium against placebo. Results showed that FDTs of diclofenac potassium with durable structure and desirable taste can be prepared using both fillers and binders but tablets prepared with Di-Pac had a better taste so the tablet formulation containing Di-Pac was chosen for in vivo experiments. Placebo controlled in vivo trial demonstrated that 50 mg diclofenac potassium, administered as a single dose of FDTs or commercial tablets, was effective in relieving the pain and both of them were superior to placebo.

Penetration of topically applied diclofenac and ketorolac into the aqueous humour and subretinal fluid: randomized clinical trial.

OBJECTIVE: To determine the level of intraocular penetration of diclofenac sodium and ketorolac tromethamine into the aqueous humour and subretinal fluid. DESIGN: Prospective randomized clinical trial. PARTICIPANTS: Twenty eyes scheduled for retinal detachment surgery and 17 eyes scheduled for cataract surgery. METHODS: Patients with retinal detachment were randomly assigned to receive either topical ketorolac (n = 11) or topical diclofenac (n = 9). Subretinal fluid samples were collected 30-60 minutes after the administration of the last dose. In addition, 17 patients with cataract were randomly assigned to receive topical ketorolac (n = 9) or topical diclofenac (n = 8). The aqueous humour samples were collected 30 minutes after the administration of the last dose. Drug concentrations were determined by high-performance liquid chromatography fluorescence. RESULTS: The mean diclofenac concentration in the subretinal fluid was 42.31 (SD 24.89) ng/µL. Ketorolac was undetectable in the subretinal fluid in all patients who received it because ketorolac tromethamine levels were under the limit of detection. In the aqueous humour, mean diclofenac concentration was 4.98 (SD 4.56) ng/µL, and mean ketorolac concentration was 20.17 (SD 12.21) ng/µL. Topical administration of diclofenac sodium yielded 8.4 times greater drug concentration in the subretinal fluid than in the aqueous humour. Aqueous humour concentrations of ketorolac were higher than those of diclofenac (p = 0.019). CONCLUSIONS: The concentration in the subretinal fluid of topically applied diclofenac was higher than that of ketorolac; and topical ketorolac penetrated into the aqueous humour better than diclofenac did. This suggests that diclofenac can be used more effectively in events related to posterior segment and ketorolac in anterior segment events.

Penetration of topically applied ciprofloxacin and ofloxacin into the aqueous humor and vitreous.

PURPOSE: To determine the intraocular penetration of topical drops of 2 antibiotics, ciprofloxacin 0.3% and ofloxacin 0.3%, into the aqueous humor and vitreous and to relate these levels to the miminum inhibitory concentration (MIC(90)) for organisms associated with ocular bacterial infections. SETTING: Department of Ophthalmology, Ankara Hospital, and Department of Pharmacology, Faculty of Medicine, Hacettepe University, Ankara, Turkey. METHODS: This prospective randomized clinical trial comprised 18 patients having cataract surgery, all with an intact corneal epithelium. The patients were randomly assigned to receive topical ciprofloxacin 0.3% (n = 10) or topical ofloxacin 0.3% (n = 8) 1 drop every 15 minutes 5 times and every 30 minutes 3 times before surgery. Aqueous and vitreous samples (if vitreous loss occurred during the cataract surgery) were collected 30 minutes after the administration of the last dose. Drug concentrations were determined by high-performance liquid chromatography (HPLC) fluorescence. RESULTS: All patients had detectable drug concentrations in the aqueous humor and vitreous measurable by HPLC. The mean aqueous humor concentration of ciprofloxacin was 1.13 microg/mL +/- 1.90 (SD) and the mean vitreous concentration, 0.23 +/- 0.06 microg/mL. Topical administration of ciprofloxacin yielded 4.9 times more drug concentration in the anterior chamber than in the vitreous. The mean aqueous concentration of ofloxacin was 2.06 +/- 1.06 microg/mL and the mean vitreous concentration, 0.46 +/- 0.10 microg/mL. Topical administration of ofloxacin yielded 4.7 times more drug concentration in the anterior chamber than in the vitreous. Aqueous humor concentrations of ofloxacin and ciprofloxacin were not statistically significantly different (P =.353). Intravitreal concentrations of ofloxacin were statistically significantly higher than those of ciprofloxacin (P =.001). CONCLUSIONS: Topical ofloxacin 0.3% penetrated better than topical ciprofloxacin 0.3% into the anterior chamber and vitreous in noninflamed eyes. Both drugs were above the MIC(90) for most ocular pathogens in the anterior chamber. The mean concentration in the vitreous of topically applied ofloxacin 0.3% was statistically significantly higher than that of ciprofloxacin 0.3%, but it was not sufficiently above the MIC(90) for most ocular pathogens in terms of empirical endopthalmitis therapy.

Effects of terfenadine and diphenhydramine on the CYP2D6 activity in healthy volunteers.

The aim of this study was to investigate the effects of two antihistaminic drugs, terfenadine and diphenhydramine on CYP2D6 activity by using debrisoquine as a model substrate. The study was carried out as an in vivo single-dose study in 12 young, healthy men. All volunteers had previously been identified as debrisoquine-extensive metabolizers. The volunteers took increasing single oral doses of one of the two antihistaminic drugs in randomized order, at weekly intervals, followed 1 h later by debrisoquine test. Terfenadine and diphenhydramine were given in the doses of 60 and 120 mg; 100 and 150 mg, respectively. The 8-hr urinary concentrations of debrisoquine and 4-hydroxydebrisoquine were determined by high-performance liquid chromatography (HPLC). With increasing doses of terfenadine and diphenhydramine, there was no statistically significant increase in the debrisoquine metabolic ratios (P > 0.05, Page's test for trend). The difference between the median debrisoquine metabolic ratios before and after treatments with terfenadine or diphenhydramine were not statistically significant (Wilcoxon's test). This investigation indicates that single-dose administration of diphenhydramine or terfenadine has no effect on the CYP2D6-mediated hydroxylation of debrisoquine in healthy volunteers.

Determination of betaxolol in human aqueous humour by high-performance liquid chromatography with fluorescence detection.

A reversed-phase high-performance liquid chromatographic method is described for the determination of betaxolol in human aqueous humour. Betaxolol and the internal standard metoprolol were extracted with cyclohexane and separated on a reversed-phase column (Luna C(18), 250 x 4.6 mm, 5 microm) with a mobile phase containing acetonitrile-phosphate buffer (40:60, v/v) at a flow-rate of 0.8 ml/min. The column effluent was monitored with a fluorescence detector at 227 nm (excitation) and 301 nm (emission). The retention times for metoprolol and betaxolol were 3.55 and 5.63 min, respectively. The recovery from aqueous humour was found to be 71.6% for betaxolol at 1.25 microg/ml. The within-day and day-to-day accuracy values were in the range of 96.17-105.2% for betaxolol at 0.1, 4 and 12 microg/ml (n=6), within-day and day-to-day precision values were less than 10% for betaxolol at the concentrations given above. The detection limit corresponding to the signal-to-noise ratio of 3:1 was 15 ng/ml. The presented method was suitable for measuring betaxolol levels in human aqueous humour samples obtained from patients after topical administration.