A comparative permeation/release study of different testosterone gel formulations

The major indication for testosterone (T) treatment is male hypogonadism that is characterized by low serum T concentrations. Although a recently developed hydroalcoholic gel, Androgel®, containing 1% T addresses many of the problems associated with the more conventional formulations, the bioavailability of T is only 10% requiring 5 to 10 g of gel to be applied daily. The present study was performed to investigate the effect of isopropyl alcohol (IPA) content as a penetration enhancer based on its ability to prevent skin dryness and in turn to increase T permeation from hydroalcoholic gels. Five different hydroalcoholic gel formulations, containing 1% T and carbopol as the gel-forming polymer, were formulated by varying the amount of IPA. The release of T from each gel, including Androgel®, was studied in vitro on Franz diffusion cells using cellulose ester and Celgard® 2400 as synthetic membranes and hairless guinea pig skin as a natural membrane. The amount of drug released from the gels was analyzed using an HPLC-UV method. The results of release/permeation studies on guinea pig skin showed that all the gels were similar to Androgel®, indicating that the addition of IPA does not affect the release of T from hydroalcoholic gels. Although no statistical significant difference was seen, the release profiles of the gels showed a trend of increasing release of T with increasing concentration of IPA. Thus, IPA does have a potential to increase the bioavailability of T from hydroalcoholic gels.     

Ex vivo study of transdermal permeation of four diclofenac salts from different vehicles

The ex vivo permeation of diclofenac was studied using four different salts (sodium, potassium, diethylamine, and epolamine) dissolved in four different solvents (water, propylene glycol (PG), Transcutol, and oleic acid (OA)) as donor phases through a human skin membrane. The four salts show different solubility values and different behavior in the four solvents, which are also permeation enhancers and this fact further is connected to the permeation results. The same order of magnitude of fluxes through the membrane as those previously reported for acidic diclofenac released from buffer solutions of pH >7 were found, taking into account differences originated by different membranes and other parameters tested in the experiments. Saturation concentration for the four salts in different solvents, necessary to calculate permeation coefficients, was critically evaluated; a short discussion made it possible to explain that corrections in the solubility values must be considered, related to the complex behavior in solution of these salts. Statistical processing of the experimental data suggests that differences between the four salts in promoting absorption of the drug is unproven; while differences are evident between the solvents, water is the most effective enhancing vehicle. Aqueous formulations containing diclofenac salt with an organic base appear to be the best combination to promote permeation in topical applications.     

In vitro permeation of diclofenac sodium from novel microemulsion formulations through rabbit skin

In order to increase topical penetration of the nonsteroidal anti‐inflammatory drug, diclofenac sodium, new microemulsion formulations were prepared to increase drug solubility and in vitro penetration of the drug. The influence of dimethyl sulfoxide and propylene glycol were also investigated as enhancers on the in vitro penetration of diclofenac sodium using Franz diffusion cells using excised dorsal rabbit skin. Factorial randomized design was performed to analyze the results of in vitro permeation studies. Microemulsions prepared with isopropyl alcohol were superior to those prepared with propanol. Enhancers had different effects depending on the formulation. Propylene glycol was superior to dimethyl sulfoxide when incorporated into isopropyl alcohol microemulsion, whereas dimethyl sulfoxide was superior to propylene glycol in propanol microemulsions. There were no observable histopathological differences between the skin of the control group and the treated groups at the light microscope level due to swelling of the skin tissue. The present study shows that microemulsion formulations containing isopropyl alcohol as co‐surfactant and propylene glycol as enhancer represent a promising approach for a topical vehicle for diclofenac sodium. Drug Dev. Res. 65:17–25, 2005. © 2005 Wiley‐Liss, Inc.     

Skin permeation of different steroid hormones from polymeric coated liposomal formulations.

In this study, the effect of various polymers (polycarbophil, chitosan-EDTA, polymeric emulsifier and carrageenan) on the permeation, the chemical and microbial stability of 17-beta-estradiol, progesterone, cyproterone acetate (cpa) and finasteride incorporated in DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) liposomes has been investigated. The liposomes contained 1% (w/w) of the steroid hormones. Standard diffusion experiments were performed. Drug stability was monitored by analysing the steroid hormone content in the different formulations over a time period of 8 weeks and visually inspecting for microbial contamination. In addition, viscosity measurements were performed. The permeation rate could be improved by addition of polymeric agents depending on their type and drug. In all tested formulations, finasteride exhibited the highest diffusion. Both the chemical and the microbial stability of the hormones were significantly improved by the polymers in comparison to the pure liposomes after an observation period of 8 weeks. After that time microbial stability was still evident for all semisolid formulations. In contrast to this in the pure liposomes already after 2 weeks the steroid drugs showed complete insufficient chemical stability and microbial contamination. Additional rheological measurements indicated an influence of the polymers and drugs on the viscosity in all formulations. The elasticity predominated in nearly all polymeric formulations.     

Comparative bioavailability of two different diclofenac formulations in healthy volunteers

The aim of the study was to assess the bioequivalence of two different diclofenac (CAS 15307-86-5) formulations (diclofenac free acid suspension as test formulation and diclofenac resinate suspension, Cataflam, as reference formulation) in 24 healthy volunteers. After an overnight fast, the volunteers received a single oral dose (50 mg) of each formulation, following an open, randomized, two-period crossover design, with a fourteen-day washout interval between doses. Serum samples were obtained over a 24-h interval post-dosing, and were analysed for their diclofenac content by HPLC-UV. No adverse effect was reported for any of the formulations administered. Geometric mean test/reference individual ratios were: 92.8% for AUC(0-24 h), 93.2% for AUC(0-infinity), 117.2% for Cmax, 131.0% for Ke and 76.2% for T1/2. The variability of Cmax parameter expressed as CV was greater than 25%. Since the 90% CI for AUC(0-24 h) mean ratio were within the 80-125% interval proposed by the Food and Drug Administration, it can be concluded that diclofenac free acid formulation is bioequivalent to diclofenac resinate formulation for the extent of absorption. Since the European Community Agency accepts a 90% CI for Cmax of 70-143%, it can be concluded that diclofenac free acid formulation is bioequivalent to diclofenac resinate formulation for both the rate and the extent of absorption after single dose administration.     

Stir bar sorptive extraction of diclofenac from liquid formulations: a proof of concept study

A new stir bar sorptive extraction (SBSE) technique coupled with HPLC-UV method for quantification of diclofenac in pharmaceutical formulations has been developed and validated as a proof of concept study. Commercially available polydimethylsiloxane stir bars (Twister™) were used for method development and SBSE extraction (pH, phase ratio, stirring speed, temperature, ionic strength and time) and liquid desorption (solvents, desorption method, stirring time etc) procedures were optimised. The method was validated as per ICH guidelines and was successfully applied for the estimation of diclofenac from three liquid formulations viz. Voltarol^® Optha single dose eye drops, Voltarol^® Ophtha multidose eye drops and Voltarol^® ampoules. The developed method was found to be linear (r = 0.9999) over 100–2000 ng/ml concentration range with acceptable accuracy and precision (tested over three QC concentrations). The SBSE extraction recovery of the diclofenac was found to be 70% and the LOD and LOQ of the validated method were found to be 16.06 and 48.68 ng/ml, respectively. Furthermore, a forced degradation study of a diclofenac formulation leading to the formation of structurally similar cyclic impurity (indolinone) was carried out. The developed extraction method showed comparable results to that of the reference method, i.e. method was capable of selectively extracting the indolinone and diclofenac from the liquid matrix. Data on inter and intra stir bar accuracy and precision further confirmed robustness of the method, supporting the multiple re-use of the stir bars.     

Evaluation of skin permeation and anti-inflammatory and analgesic effects of new naproxen microemulsion formulations

The aim of this study was to evaluate the potential application of microemulsions as a transdermal drug delivery for naproxen (Np). The pseudo-ternary phase diagrams were developed for microemulsions composed of isopropyl myristate, Span 80, Labrafil M, Labrasol, and Cremophor EL, ethanol and isopropyl alcohol and 0.5 N sodium hydroxide. The final concentration of Np in microemulsion systems was 10% (w/w). The microemulsions were characterised by conductivity, droplet size, viscosity and pH. Moreover, in vitro permeability studies were performed using diffusion cells from rat skin. The permeation rates of Np from microemulsions (M1_Np and M2_Np) were higher than the commercial (C) gel formulation. The paw oedema test was performed in rats to evaluate the anti-inflammatory activity of Np. The volume increase in paw oedema after 6 hr was 0.71 ± 0.46% with M2_Np, whereas M1_Np and C exhibited 6.48 ± 2.71% and 14.97 ± 3.15% increases in oedema, respectively. Additionally, a significant analgesic effect was detected in the hot plate and tail-flick tests for all test microemulsion and C formulations when compared with the control. Histopathological examination of the treated skin was performed to investigate changes in skin morphology. In conclusion, the microemulsion formulations, especially the M2_Np formulation, may be used as an effective alternative for the transdermal delivery of Np.     

Bioavailability study of two different verapamil formulations.

Relative bioavailability and bioequivalence of two oral verapamil preparations were investigated (dosage 80 mg, film-coated tablets as reference, dragées as test formulation). The clinical study was performed in a 2-period-cross-over design with 16 male healthy volunteers (mean age 28.8 +/- 3 years). The active metabolite norverapamil was included in the investigation. To assess bioequivalence several pharmacokinetic characteristics (i.e. AUC(o-oo), Cmax, tmax) were taken into account. Shortest 90% confidence intervals were calculated based on parametric (ANOVA, ANOVAlog) and non-parametric (Wilcoxon, Mann-Whitney) statistical tests. A positive decision for bioequivalence was accepted if the confidence intervals did not exceed the limits of 80-120% for AUC and 70-130% for Cmax. A mean relative bioavailability of 127% for the test preparation was found. Thus, bioavailability of the dragées is marked higher than bioavailability of the film-coated tablets.     

Clinical trial on the efficacy and safety of different diclofenac formulations: Multiple-unit formulations compared to enteric coated tablets in patients with activated osteoarthritis

—This double-blind, randomised, multicentre study investigated the efficacy and safety of two different dosages of a diclofenac sodium dual release capsule (150 mg or 75 mg once daily) in comparison to a standard treatment with enteric coated tablets (50 mg t.i.d.) and placebo in patients with activated osteoarthritis. Pain relief as the main efficacy variable was measured through 24 hours by means of a Visual Analogue Scale at baseline and on five assessment days during the 12 weeks of treatment. Efficacy was observed in all treatment groups with a statistically significant difference between the verum groups and placebo. The overall safety and tolerability of the active treatments was good. For the 75 mg group, a lower incidence of liver and biliary system-related side effects was reported. Considering efficacy, safety, and compliance aspects, the once daily administration of diclofenac sodium 75 mg dual release capsule is the appropriate dosage regimen for mid- and long-term treatment of osteoarthritis.     

In vitro permeation profile of a local anaesthetic compound from topical formulations with different rheological behaviour--verified by in vivo efficacy data.

The object of this study was to develop a topical cream of suitable consistency, i.e. with a high apparent yield stress, without affecting the in vitro permeation profile and the subsequent in vivo efficacy of the formulation. Different formulations of a model compound were manufactured, an oil-in-water (o/w) emulsion, a cream consisting of the o/w emulsion thickened with various concentrations of neutralised Carbopol934P gel, and a semisolid water-in-oil (w/o) emulsion. Rheological measurements were performed giving the apparent yield stress of the formulations. The in vitro permeation rate of the compound was measured, using static diffusion cells with both guinea pig and human skin as membrane. The o/w emulsion without polymer was used as reference. The in vivo efficacy of the formulations was investigated on guinea pigs by the pinprick method. The apparent yield stress of the w/o emulsion was in the same range as that of the most viscous o/w cream while the o/w emulsion behaved as a Newtonian liquid. Furthermore, the yielding property of the w/o emulsion was not as temperature-sensitive as that of the o/w cream. The permeation rate of the compound from the two emulsions, o/w and w/o, was similar at 6% (w/w), while the o/w cream resulted in a significantly lower permeation rate at the same concentration. The two emulsions produced sufficient and comparable in vivo efficacy, while the o/w cream was less efficient. In conclusion, a reversed-phase emulsion may be used to produce the appropriate apparent yield stress, without affecting the in vivo efficacy of the formulation. The viscosity of a w/o emulsion depends on the amount of the aqueous phase and the degree of dispersity. Thus, the transport of the active compound is not prevented by the excipients present in the formulation, as is the case for the o/w cream.     

Intranasal bioavailability of insulin powder formulations: effect of permeation enhancer-to-protein ratio.

The intranasal administration of powder formulations containing insulin and the permeation enhancer sodium tauro-24,25-dihydrofusidate (STDHF) were investigated in the sheep model. Both the hypoglycemic response and the serum insulin levels increased as the mole ratio of STDHF to insulin was increased from 0 to 16.8. In vitro dissolution rates of the powders and the rapid tmax (approximately 5 min) observed after intranasal administration suggest that the absorption of insulin is not dissolution limited. The bioavailabilities (F) of the powder formulations ranged from 2.9 to 37.8%. In comparison, the F values for a solution formulation with a STDHF:insulin ratio of 8.4 administered as either drops or spray were 15.7 and 37.4%, respectively. The permeation enhancer STDHF increases mucosal permeability and reduces the average molecular weight of the insulin species.     

Potential management of resistant microbial infections with a novel non-antibiotic: the anti-inflammatory drug diclofenac sodium

Diclofenac sodium (Dc), an anti-inflammatory agent, has remarkable inhibitory action both against drug-sensitive and drug-resistant clinical isolates of various Gram-positive and Gram-negative bacteria. The aim of this study was to determine the ability of Dc to protect mice from a virulent Salmonella infection. Dc injected at 1.5 microg/g and 3.0 microg/g mouse body weight significantly protected animals from the lethality of Salmonella infection. As was the case for the in vitro interaction, Dc in combination with streptomycin was even more effective. The non-antibiotic drug Dc has potential for the management of problematic antibiotic-resistant bacterial infections.     

Transbuccal permeation, anti-inflammatory activity and clinical efficacy of piroxicam formulated in different gels

In attempts to avoid the systemic side effects of piroxicam (PC) (e.g. gastrotoxicity), several buccal gel formulations containing PC were prepared and their effects on the characteristics of the drug permeation through rabbit buccal mucosa in-vitro were evaluated using a Franz-type diffusion cell. The general rank order of the total flux of 0.5% PC from gels was found to be: hydroxypropylmethylcellulose (HPMC, 2.5%) > hydroxypropylcellulose (HPC, 2.5%) >or= sodium alginate (Na alg., 7%) > methylcellulose (MC, 3%) > hydroxyethylcellulose (HEC, 1.5%) > carbopol 934 (Carb. 934, 1%) >or= sodium carboxymethylcellulose (NaCMC, 2%) > pluronic F-127 (PF-127, 20%) > polyvinyl alcohol (PVA, 10%). The effect of various penetration enhancers 1% sodium lauryl sulphate (NaLS), 3% sodium deoxycholate (NaDC), 3% sodium tauroglycocholate (NaTGC) on the rate of permeation across the excised buccal mucosa (of 0.5% PC in gels prepared using 3% MC, 2.5% HPMC or 7% Na alg. base) and histology of the buccal epithelium was also investigated. Pharmacodynamic evaluation of the anti-inflammatory activity of PC in these gel formulations (containing 3% NaDC as an enhancer) was carried out using the kaolin-induced rat paw oedema method. The results obtained indicated that PC administered in 7% Na alg. or 2.5% HPMC gel bases was significantly more effective than the 3% MC gel and oral drug solution in suppressing oedema formation in rats. Comparative clinical studies were conducted in patients with post-operative dental pain and oedema following maxillofacial operations. The results revealed that 7% Na alg. and 2.5% HPMC gel formulations applied to the buccal mucosa were slightly better than or equally effective to the orally administered commercial product (Feldene Flash) tablet) in reducing pain level, swelling and tenderness within a period of 4 days. These findings suggest that PC (0.5%) administered in the buccal gel may present a potential therapeutical use as a strong anti-inflammatory and analgesic agent.     

Reconstruction of an in vitro cornea and its use for drug permeation studies from different formulations containing pilocarpine hydrochloride.

The aim of the present contribution was to develop a functional three-dimensional tissue construct to study ocular permeation of pilocarpine hydrochloride from different formulations. The in vitro model was compared to excised bovine cornea. Modified Franz cells were used to study the transcorneal permeability. Analysis was performed by reversed-phase high-performance liquid chromatography. Comparisons of the permeation rates through excised bovine cornea and the in vitro model show the same rank order for the different formulations. The permeation coefficient, K(P), obtained with the cornea construct, is about 2-4-fold higher than that from excised bovine cornea. It is possible to reconstruct bovine cornea as an organotypic culture and also to use this construct as a substitute for excised bovine cornea in drug permeation studies in vitro.     

The treatment of depression with different formulations of venlafaxine: a comparative analysis

Venlafaxine is the first of a group of antidepressants that show dual reuptake inhibition of serotonin and noradrenaline (SNRIs). Originally marketed in an immediate release (IR) formulation a microencapsulated, extended release (XR) formulation is now available. Significant differences exist between these two formulations with respect to pharmacokinetic parameters which have an impact on clinical use. The XR has lower maximum plasma concentrations (Cmax) and achieves these at a later time (higher Tmax). The longer apparent elimination half-life of the drug after single XR doses suggests that it is suitable for once daily dosing compared with the twice daily dosing regimen required by the IR formulation. With respect to antidepressant efficacy the XR formulation is equivalent to other marketed antidepressants and to the IR formulation. Consistent with its pharmacokinetic properties the use of the XR formulation is associated with less nausea and dizziness at the initiation of therapy. While in clinical usage XR might be expected to increase compliance with medication and to reduce discontinuation syndromes there are few comparative studies for which this has been evaluated. The XR formulation of venlafaxine is no worse than the IR form with respect to tolerability and offers some benefits to patients in terms of ease of use. On the other hand there does not appear to be any increase in the efficacy of the active agent.     

Hydrate modifications of the non-steroidal anti-inflammatory drug diclofenac sodium: Solid-state characterisation of a trihydrate form

Diclofenac sodium is a non-steroidal anti-inflammatory drug widely used in painful and inflammatory diseases. It can exist in different hydrate phases. By exposure to different conditions of temperature and relative humidity can be isolated a trihydrate form never described in literature. The methods of preparation of the trihydrate form (named DSH3) were described and its physico-chemical properties were investigated. Data from FTIR spectroscopy, X-ray powder diffraction and thermal analysis were used for identification and characterisation of DSH3 in comparison with the anhydrous form (DS, the commercial form) and the hydrate form DSH (obtained by exposure of DS to relative humidity even below 60% and already described and characterised in a previous article of the same authors). Intrinsic dissolution studies were performed to compare the pharmaceutical properties of DS and DSH with DSH3, since this form was accidentally found on the Italian market as active pharmaceutical ingredient (API). This work stresses the importance of assessing the correct crystalline form also in API of well-established use to guarantee quality, safety and efficacy of the final dosage form. Furthermore, this study suggests that isomorphic hydrate forms with a different dislocation of water within the crystal structures can exist.     

Biomarker assessment of toxicity with miniaturised bioassays: diclofenac as a case study

The development of suitable biomarker-based microbioassays with model species with ecological relevance would help increase the cost-efficiency of routine environmental monitoring and chemical toxicity testing. The anti-inflammatory drug diclofenac has been widely reported in the environment but ecotoxicological data are scarce. The aim of this work is to assess the acute and chronic sublethal toxicity of diclofenac in relevant taxa of aquatic and riparian ecosystems (the fish Danio rerio and the fern Polystichum setiferum). Reliable biomarkers of cell viability (mitochondrial activity), plant physiology (chlorophyll), growth (DNA content) or oxidative damage (lipid peroxidation) were assessed as sensitive endpoints of toxicity. DNA quantification shows that diclofenac induces acute lethal phytotoxicity at 24 and 48 h (LOECs 30 and 0.3 μg l⁻¹, respectively). Hormetic effects in mitochondrial activity in spores of Polystichum setiferum mask lethality, and adverse effects are only observed at 48 h (LOEC 0.3 μg l⁻¹). In chronic exposure (1 week) LOEC for DNA is 0.03 μg l⁻¹. Mitochondrial activity shows a strong hormetic stimulation of the surviving spore population (LOEC 0.3 μg l⁻¹). Little changes are observed in chlorophyll autofluorescence (LOEC 0.3 μg l⁻¹). A very short exposure (90 min) of zebrafish embryos induces a reduction of lipid peroxidation at 0.03 μg l⁻¹. Environmental concentrations of diclofenac can be deleterious for the development of significant populations of sensitive individuals in aquatic and riparian ecosystems.     

Increased absorption rate of diclofenac from fast acting formulations containing its potassium salt.

Diclofenac (CAS 15307-86-5) is a non-steroidal anti-inflammatory drug largely used, mainly to relief pain of various origin. Diclofenac is present on the market as free acid, as sodium salt (CAS 15307-79-6) and as potassium salt (CAS 15307-81-0). The last salification form has shown a prompter absorption rate and a faster onset of analgesic activity than the acid form and sodium salt. This paper extensively reviews three trials carried out on healthy volunteers, where potassium salt of diclofenac present in three fast-acting formulations, namely sachets (Trial 1), tablets (Trial 2) and oral drops (Trial 3), were compared to reference tablet formulations from the market. A very fast absorption rate was encountered with the three test formulations, with the peak reached in one case 5 min and in most cases within 10-15 min after dosing. The quick absorption rate of test formulations was attributed to the special combination of the salt of diclofenac with a dynamic buffering agent, namely bicarbonate, present in the test formulations and covered by an international patent. The prompt absorption of diclofenac from the new fast-acting formulations was accompanied by the presence of only one peak, whereas the reference formulations produced in most cases two peaks, as widely described in literature. This finding suggested the hypothesis that the absorption of test formulations should occur in a shorter tract of the gut. The faster absorption of diclofenac from the three fast-acting formulations is expected to produce a faster onset of analgesic action, which highlights these new formulations as particularly indicated to relief pain of any origin.     

Evaluation of transcutol as a clonazepam transdermal permeation enhancer from hydrophilic gel formulations

The influence of diethyleneglycol monoethyl ether (transcutol), alone or in combination with propylene glycol, on clonazepam permeation through an artificial membrane and excised rabbit ear skin from Carbopol hydrogels was investigated. Drug kinetic permeation parameters were determined for both series of experiments and compared. Rheological characteristics, drug solubility and membrane/vehicle partition coefficient for each gel formulation were also determined, and their role in the formulation performance was investigated. Both series of experiments showed an increase of drug permeation as a function of transcutol content in the formulation. The combination of transcutol and propylene glycol resulted in a synergistic enhancement of clonazepam flux. A different trend was found in experiments with gels containing mixtures of the two enhancers, where an increase (in the case of artificial membrane) or a decrease (in the case of rabbit ear skin) of drug permeation was found by increasing the transcutol/propylene glycol ratio in the mixture. Such a result is explained on the basis of the particular mechanism of action demonstrated for transcutol which associates the increase of drug solubility to the potent effect of a depot in the skin.