Pharmacokinetic and local tissue disposition of [14C]sodium diclofenac following iontophoresis and systemic administration in rabbits

Carbomer Hydrogels with Microencapsulated α-Tocopherol: Focus on the Biocompatibility of the Microcapsules, Topical Application Attributes, and In Vitro Release Study

The microencapsulation of α-tocopherol based on the complex coacervation of low-molecular-weight chitosan (LMWC) and sodium lauryl ether sulphate (SLES) without harmful crosslinkers can provide biocompatible carriers that protect it from photodegradation and air oxidation. In this study, the influence of the microcapsule wall composition on carrier performance, compatibility with a high-water-content vehicle for topical application, and release of α-tocopherol were investigated. Although the absence of aldehyde crosslinkers decreased the encapsulation efficiency of α-tocopherol (~70%), the variation in the LMWC/SLES mass ratio (2:1 or 1:1) had no significant effect on the moisture content and microcapsule size. The prepared microcapsule-loaded carbomer hydrogels were soft semisolids with pseudoplastic flow behavior. The integrity of microcapsules embedded in the hydrogel was confirmed by light microscopy. The microcapsules reduced the pH, apparent viscosity, and hysteresis area of the hydrogels, while increasing their spreading ability on a flat inert surface and dispersion rate in artificial sweat. The in vitro release of α-tocopherol from crosslinker-free microcapsule-loaded hydrogels was diffusion-controlled. The release profile was influenced by the LMWC/SLES mass ratio, apparent viscosity, type of synthetic membrane, and acceptor medium composition. Better data quality for the model-independent analysis was achieved when a cellulose nitrate membrane and ethyl alcohol 60% w/w as acceptor medium were used.

Iontophoretic Mediated Intraarticular Delivery of Deformable Liposomes of Diclofenac Sodium

BACKGROUND AND OBJECTIVE

Topical therapy is ineffective in the case of Musculoskeletal Disorders (MSD) as it is not able to maintain therapeutic levels of the drug in the affected joint due to its inability to surpass the dermal circulation and penetrate into deeper tissues. One of the approaches to enhance deep tissue penetration of drugs is to increase drug delivery much above the dermal clearance. The objective of the present work was to formulate negatively charged Deformable Liposomes (DL) of Diclofenac Sodium (DS) using biosurfactants and target the same to the synovial fluid by application of iontophoresis.

METHODS

Deformable liposomes loaded with diclofenac sodium were formulated and characterized for surface morphology, particle size distribution, zeta potential and entrapment efficiency. In vitro permeation of the diclofenac from aqueous solution, conventional liposomes, and deformable liposomes under iontophoresis was performed using Franz diffusion cells and compared to passive control. Intraarticular microdialysis was carried out to determine the time course of drug concentration in the synovial fluid at the knee-joint region of the hind limb in Sprague Dawley rats.

RESULTS

The vesicles were found to display a high entrapment (> 60%) and possess a negative zeta potential lower than -30 mV. The size of the vesicles was varied from 112.41 ± 1.42 nm and 154.6 ± 3.22 nm, demonstrated good stability on the application of iontophoresis. The iontophoretic flux values for the DS aqueous solution, conventional liposomes and deformable liposomal formulation were found to be 7.55 ± 0.42, 16.75±1.77and 44.01 ± 3.47 μg/ cm² h^-1, respectively. Deformable liposomes were found to display an enhancement of 5.83 fold compared to passive control. Iontophoresis was found to enhance the availability of DS deformable liposomes (0.56 ± 0.08 μg.h/ml) in the synovial fluid by nearly 2-fold over passive delivery (0.29 ± 0.05 μg.h/ml).

CONCLUSION

Results obtained indicate that iontophoretic mediated transport of deformable liposomes could improve the regional bioavailability of diclofenac sodium to the synovial joints, an efficient mode for treating MSD in the elderly.

Effect of terpenes on transdermal iontophoretic delivery of diclofenac potassium under constant voltage

OBJECTIVE

The aim of the study was to enhance the transdermal delivery of diclofenac potassium (DP) from hydrogels by constant voltage iontophoresis (CVI). The other objective was to establish the safety and efficacy of CVI in rats.

MATERIALS AND METHODS

Hydrogels of DP were developed using hydroxyethyl cellulose as matrix material and geraniol, l-menthol and thymol as iontophoretic efficiency enhancers (IEE). In vitro permeation of hydrogels under CVI (1.5 V) was performed in Franz diffusion cells across porcine skin. The ability of CVI to deliver therapeutic amount of DP in vivo was assessed in rat paw edema model.

RESULTS

CVI significantly (p < 0.05) increased the steady state flux of DP compared to the passive. The hydrogels containing geraniol and l-menthol enhanced the iontophoretic flux of DP by ∼4.75 and ∼4.49 fold, respectively compared to passive control. The in vivo studies indicated that CVI in combination with IEE, significantly reduced (p < 0.05) area under the curve (AUC) of % inflammation compared to passive treatment. An excellent correlation (r = 0.996) was noted between in vitro flux values and AUC of % inflammation.

CONCLUSION

The preclinical studies conclusively demonstrated that CVI in combination with IEE's such as geraniol or l-menthol has the potential to safely deliver therapeutic amounts of DP.

Iontophoresis driven concentrations of topically administered diclofenac in skeletal muscle and blood of healthy subjects

PURPOSE

The present open single-centre, descriptive and comparative pharmacokinetic study aimed to investigate the efficacy of iontophoresis to enhance transdermal delivery by measuring concentration vs. time profiles of diclofenac in local tissue and in plasma in two separate study periods.

METHODS

Period 1 determined diclofenac concentrations in both calf muscles simultaneously by using microdialysis after applying diclofenac gel topically as a single dose of 5 g with or without iontophoresis in eight healthy volunteers. In period 2, the same dose was applied to another 8 volunteers to determine plasma concentrations of diclofenac either with or without iontophoresis in a cross over design.

RESULTS

In period 1, tissue concentrations were found to be under the limit of detection of 0.5 ng/ml both with and without iontophoresis in all subjects. In period 2, after iontophoresis in 75% of study participants, plasma concentrations of diclofenac could be determined, but only in 25% without iontophoresis. Although area under the concentration-time-curve (AUC, 187.97 ± 315.92 vs. 22.92 ± 42.44 ng*min/ml) and maximum concentration (Cmax, 2.06 ± 3.79 vs. 0.22 ± 0.41 ng/ml) values showed a numerically clear trend for higher values with iontophoresis compared to passive diffusion, no significant difference could be found due to high inter-individual variability. In total, 18.75% of all subjects presented adverse events.

CONCLUSIONS

Despite a higher percentage of subjects showed detectable plasma levels of diclofenac after iontophoresis, iontophoresis failed to achieve potentially more effective topical concentrations. The typical mechanism of iontophoresis like electromigration, electroosmosis and increased subcutaneous circulation could be responsible for the results of the present observation. Additional clinical studies are needed to justify the transdermal delivery of diclofenac by using iontophoresis.

Potential use of iontophoresis for transdermal delivery of NF-kappaB decoy oligonucleotides

Topical application of nuclear factor-kappaB (NF-kappaB) decoy appears to provide a novel therapeutic potency in the treatment of inflammation and atopic dermatitis. However, it is difficult to deliver NF-kappaB decoy oligonucleotides (ODN) into the skin by conventional methods based on passive diffusion because of its hydrophilicity and high molecular weight. In this study, we evaluated the in vitro transdermal delivery of fluorescein isothiocyanate (FITC)-NF-kappaB decoy ODN using a pulse depolarization (PDP) iontophoresis. In vitro iontophoretic experiments were performed on isolated C57BL/6 mice skin using a horizontal diffusion cell. The apparent flux values of FITC-NF-kappaB decoy ODN were enhanced with increasing the current density and NF-kappaB decoy ODN concentration by iontophoresis. Accumulation of FITC-NF-kappaB decoy ODN was observed at the epidermis and upper dermis by iontophoresis. In mouse model of skin inflammation, iontophoretic delivery of NF-kappaB decoy ODN significantly reduced the increase in ear thickness caused by phorbol ester as well as the protein and mRNA expression levels of tumor necrosis factor-alpha (TNF-alpha) in the mice ears. These results suggest that iontophoresis is a useful and promising enhancement technique for transdermal delivery of NF-kappaB decoy ODN.

Pharmacokinetic studies of meloxicam following oral and transdermal administration in Beagle dogs

AIM

The potential for topical delivery of meloxicam was investigated by examining its pharmacokinetic profiles in plasma and synovial fluid following oral and transdermal administration in Beagle dogs.

METHODS

The experiment was a two-period, crossover design using 6 Beagle dogs. Meloxicam tablets were administered orally at a dose of 0.31 mg/kg, and meloxicam gel was administered transdermally at a dose of 1.25 mg/kg. Drug concentrations in plasma and synovial fluid were determined by liquid chromatography-tandem mass spectrometry (LC/MS/MS). The pharmacokinetic parameters were calculated using the Topfit 2.0 program.

RESULTS

The pharmacokinetic results showed that AUC(0-t) (23.9+/-8.26 microg.h.mL(-1)) in plasma after oral administration was significantly higher than after transdermal delivery (1.00+/-0.43 microg.h.mL(-1)). In contrast, the ratio of the average concentration in synovial fluid to that in plasma following transdermal administration was higher than that for an oral delivery. The synovial fluid concentration in the treated leg was much higher than that in the untreated leg, whereas the synovial fluid concentration in the untreated leg was similar to the plasma concentration.

CONCLUSION

The high concentration ratio of synovial fluid to plasma indicates direct penetration of meloxicam following topical administration to the target tissue. This finding is further supported by the differences observed in meloxicam concentrations in synovial fluid in the treated and untreated joints at the same time point. Our results suggest that transdermal delivery of meloxicam is a promising method for decreasing its adverse systemic effects.Acta Pharmacologica Sinica (2009) 30: 1060-1064; doi: 10.1038/aps.2009.73; published online 8 June 2009.

Review of the pharmaceutical properties and clinical effects of the topical NSAID formulation, diclofenac epolamine

BACKGROUND

Topical formulations of non-steroidal anti-inflammatory drugs (NSAIDs), in particular diclofenac (DI), have become popular for treating various acute and chronic painful inflammatory conditions.

OBJECTIVE

To perform a literature review of (1) the use of topical NSAIDs; (2) the pharmaceutical, pharmacokinetic and pharmacodynamic properties of a medicated plaster (patch) containing diclofenac epolamine (DI-EP, Flector Tissugel, Flector patch) compared with other formulations of topical NSAIDs; and (3) evaluation of the clinical findings from studies with this novel DI-EP patch.

OUTCOMES

(1) Pharmacokinetic studies involved determination of DI from DI-EP and separately epolamine (EP) and the epoxide metabolite (N-oxide-EP) in laboratory animals and humans; the latter being the major metabolite in humans. About 2% of DI is absorbed by the skin in humans and is excreted in the urine. Maximum plasma concentrations of 17.4 ng/mL DI are reached at 5.4 hours (approximate steady state conditions); the plasma elimination half-time (t(1/2)) being 26.4 hours. Low systemic levels of DI and EP are produced from DI-EP. Pronounced accumulation of DI occurs in the muscle layers and in synovial fluids of arthritic patients; (2) No significant toxicity occurs from EP nor N-oxide-EP, while that of oral DI-EP was similar to that from DI; and (3) In acute musculoskeletal conditions (sprains, tendonitis and sports injuries) and osteoarthritis DI-EP patches control pain and signs of joint or physical injury compared with placebo controls by 3-5 days with almost complete pain relief at 14 days. DI-EP was shown to have equivalent therapeutic effect to another DI diethylammonium gel formulation (Voltaren Emulgel). There were no reports of serious adverse events in the gastro-intestinal (GI) tract, kidneys or liver from DI-EP. Mild GI symptoms and skin reactions occur in 2 and 10% of patients, respectively.

CONCLUSIONS

The patch delivery of DI in DI-EP affords controlled delivery of the active drug in contrast to that from application of gels or ointments of NSAIDs.

Iontophoresis of dexamethasone phosphate: competition with chloride ions

The objective was to study the competition of chloride released from a Ag/AgCl cathode on the iontophoretic delivery of dexamethasone phosphate (Dex-Phos). Iontophoresis of Dex-Phos was performed in side-by-side diffusion cells (0.78 cm(2)) using pig skin. A 0.3 mA constant current was applied via Ag/AgCl electrodes. The amounts of Dex-Phos and dexamethasone (Dex) were also quantified in the stratum corneum (SC), using tape-stripping, after passive and iontophoretic delivery. The profiles of Dex-Phos and Dex, as a function of position in the SC, were deduced. The iontophoretic delivery of Dex-Phos from pure water was unaffected by the accumulation of Cl- released by the donor cathode when the drug's concentration was 4.25 mM to 17 mM. At 0.85 mM, however, Cl- competition was significant and the drug flux was significantly reduced. Formulation of the drug in the presence of Cl- resulted in a non-linear dependence of flux on the molar fraction of the drug. Tape-stripping experiments confirmed the enhanced delivery of Dex-Phos by iontophoresis relative to passive diffusion, with Dex-Phos concentration greater inside the barrier post-iontophoresis than that in the donor. The latter observation could explain the robustness of Dex-Phos delivery to the presence of Cl- in the donor solution.

The Local Antinociceptive Actions of Nonsteroidal Antiinflammatory Drugs in the Mouse Radiant Heat Tail-Flick Test

BACKGROUND

While many preclinical models detect the analgesic activity of nonsteroidal antiinflammatory drugs (NSAIDs), the radiant heat tail-flick response has repeatedly been insensitive to this class of drugs. As the tail-flick test involves nociceptive processing at spinal circuits with supraspinal modulation, it seems reasonable to assume that the NSAIDs should not modify strong nociceptive stimuli, since the primary site of action of NSAIDs is likely to be in the periphery.

METHODS

We injected 3-300 mug of diclofenac, dipyrone, ketorolac, lysine acetyl salicylate, and sodium salicylate intradermally into mice tails and evaluated the tail-flick response to radiant heat. These results were compared with intraperitoneally injected controls. We also evaluated the ability of naloxone to reverse the observed effects.

RESULTS

Intradermal injection of each NSAID produced a dose-dependent increase in tail-flick latency. Intraperitoneal NSAIDs injection produced no antinociceptive effects. Naloxone pretreatment had no effect on the antinociceptive effects of intradermal diclofenac, ketorolac, lysine acetyl salicylate, and sodium salicylate. Naloxone completely blocked the antinociceptive effects of intradermal dipyrone.

CONCLUSIONS

Local, but not systemic, administration of NSAIDs produced antinociception in the tail-flick thermal assay. The endogenous opioid system contributes to the peripheral antinociceptive effects of dipyrone, but not to that of diclofenac, ketorolac, lysine acetyl salicylate, or sodium salicylate, suggesting differences in the mechanisms of action among the NSAIDs.

Study of the percutaneous penetration of flurbiprofen by cutaneous and subcutaneous microdialysis after iontophoretic delivery in rat

The percutaneous penetration of flurbiprofen delivered by iontophoresis was investigated in the hairless rat. Unbound concentrations of flurbiprofen in dermis and subcutaneous tissue were continuously measured by on-line microdialysis. Simultaneously, a conventional blood sampling was performed. Linear microdialysis probes were implanted in dermis and in subcutaneous tissue at a depth of 398.3 +/- 15.3 and 1878 +/- 35.8 microm, respectively. Commercial patches were used to deliver flurbiprofen for 15 min at a current density of 0.4 mA/cm(2). In vivo recoveries of both probes, determined by using naproxen as retrodialysis calibrator, were 26.0 +/- 0.3 and 72.9 +/- 0.7% for dermal and subcutaneous probe, respectively. After iontophoretic delivery, a gradient in mean tissue unbound concentrations was observed, with a C(max) in dermis of 8.7 +/- 0.4 microg/mL as compared with subcutaneous C(max) of 0.5 +/- 0.1 microg/mL. The area under the unbound concentration curve in dermis was 13-fold higher than that in the subcutaneous tissue. Total plasma concentration curves showed a rapid absorption phase with a T(max) of 30 min and C(max) of 1.8 +/- 0.1 microg/mL. In conclusion, iontophoresis delivery was demonstrated to be efficient to deliver a high amount of flurbiprofen in dermis and underlying tissue with a fast input rate whereas maintaining a low plasma exposure.

Iontophoretic drug delivery

The composition and architecture of the stratum corneum render it a formidable barrier to the topical and transdermal administration of therapeutic agents. The physicochemical constraints severely limit the number of molecules that can be considered as realistic candidates for transdermal delivery. Iontophoresis provides a mechanism to enhance the penetration of hydrophilic and charged molecules across the skin. The principal distinguishing feature is the control afforded by iontophoresis and the ability to individualize therapies. This may become significant as the impact of interindividual variations in protein expression and the effect on drug metabolism and drug efficacy is better understood. In this review we describe the underlying mechanisms that drive iontophoresis and we discuss the impact of key experimental parameters-namely, drug concentration, applied current and pH-on iontophoretic delivery efficiency. We present a comprehensive and critical review of the different therapeutic classes and molecules that have been investigated as potential candidates for iontophoretic delivery. The iontophoretic delivery of peptides and proteins is also discussed. In the final section, we describe the development of the first pre-filled, pre-programmed iontophoretic device, which is scheduled to be commercialized during the course of 2004.

The antinociceptive effect of iontophoretic direct application of diclofenac to arthritic knee-joints of rats

This study compared the antinociceptive effect produced by cathodic iontophoresis of sodium diclofenac close to an arthritic knee-joint in rats with that of systemic application. Arthritic nocifensive incapacitation was induced by LPS (1 microg) injection into a knee-joint previously (72 h) primed with carrageenan (300 microg). Diclofenac (0.1, 0.25 and 0.5 mg/kg) given intraperitoneally 1 h after LPS injection caused dose-dependent inhibition of incapacitation. Diclofenac iontophoresis was performed by varying either the current density (0.1, 0.2, and 0.3 mA/cm2) or the duration of application (4, 10, 20 and 30 min) of a polyvinylpirrolydone-hydroxymethylcellulose gel containing 1% sodium diclofenac. A clear, current density-dependent effect was observed for 0.1, 0.2 and 0.3 mA/cm2 (10 min period), which was similar to the effect observed for the intraperitoneal application of 0.1, 0.25 and 0.5 mg/kg doses. Combining different application periods with different current densities, in a manner that resulted in the same total current (1.6 mA*min) application, did not produce similar therapeutic effects, but the antinociceptive effect was directly proportional to the current density. The ipsilateral iontophoresis (0.25 mA/cm2 x 10 min or 0.5 mA/cm2 x 4 min) of diclofenac produced an effect significantly greater than the same contralateral application (p<0.05). In conclusion, our results suggest that the therapeutic effect depends on the current density but not on the application time, and also that the iontophoretic, direct application to the inflamed knee-joint enhances the therapeutic effect probably as a result of the direct delivery of the drug.

Characterization of the permselective properties of rabbit skin during transdermal iontophoresis

The use of iontophoresis to enhance transdermal transport of drugs necessitates further investigations on the membrane used to simulate human skin because one of the transport mechanisms involved, electroosmosis, strictly depends on the properties of the skin (i.e., its isoelectric point, IP). The aim of this work was to characterize rabbit ear skin permselectivity by measuring the sodium transport number at different pH values. This method allowed us to estimate the skin IP. To confirm the validity of the method, mannitol flux was measured. In addition, the sodium transport number method was applied to the study of human skin and a model drug iontophoretic flux through rabbit and human skin was evaluated. The results indicate that rabbit ear skin behaves as a permselective membrane, with an IP between 2 and 3. The same result was obtained using human skin. The mannitol flux data confirm that the direction of electroosmotic flow at physiological pH is in the anode-to-cathode direction. Finally, permeation experiments performed with a model drug showed that the relative electroosmotic and electrorepulsive contributions to the total flux are the same for human and rabbit skin. It can be concluded that rabbit ear skin is a suitable model for the study of iontophoretic permeation of drugs.

Effect of Mixed Micelle Formulations Including Terpenes on the Transdermal Delivery of Diclofenac

The significant inhibitory action of diclofenac formulated in mixed micelles of lecithin with cholate or deoxycholate was observed on the rat hind paw edema induced by carrageenan. In the primary stage, mixed micelle formulation of deoxycholate was more effective compared with that of cholate. However, in the final term, the inhibitory action was similar in both formulations. In a previous study, the flux of diclofenac was greater in the mixed micelle formulation of deoxycholate compared with that of cholate. It was suggested that the permeation rate of diclofenac through skin was proportional to the pharmacological activity. The hind paw edema was quickly inhibited when cyclic monoterpene such as d-limonene or l-menthol was included in the formulations. All the micelle formulations significantly decreased the value of AUC estimated the hind paw thickness-time profile. This suggests that the micelle formulation of cholate in addition to deoxycholate showed significant anti-inflammatory activity to hind paw edema of rats. Incorporation of d-limonene or l-menthol was more effective on the decrease of AUC. A pharmacological study revealed that micelle formulations were able to reduce the skin irritation of chemicals.