In vitro studies on transdermal permeation of butorphanol

Effect of borneol on the transdermal permeation of drugs with differing lipophilicity and molecular organization of stratum corneum lipids

The aim of the present paper was to investigate the promoting activity of borneol on the transdermal permeation of drugs with differing lipophilicity, and probe its alterations in molecular organization of stratum corneum (SC) lipids. The toxicity of borneol was evaluated in epidermal keratinocyte HaCaT and dermal fibroblast CCC-HSF-1 cell cultures and compared to known enhancers, and its irritant profile was also assessed by transepidermal water loss (TEWL) evaluation. The promoting effect of borneol on the transdermal permeation of five model drugs, namely 5-fluorouracil, antipyrine, aspirin, salicylic acid and ibuprofen, which were selected based on their lipophilicity denoted by logp value, were performed using in vitro skin permeation studies. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) was employed to monitor the borneol-induced alteration in molecular organization of SC lipids. The enhancer borneol displayed lower cytotoxicity or irritation in comparison to the well-established and standard enhancer Azone. Borneol could effectively promote the transdermal permeation of five model drugs, and its enhancement ratios were found to be parabolic curve with the logp values of drugs, which exhibited the optimum permeation activity for relatively hydrophilic drugs (an estimated logp value of -0.5 ∼0.5). The molecular mechanism studies suggested that borneol could perturb the structure of SC lipid alkyl chains, and extract part of SC lipids, resulting in the alteration in the skin permeability barrier.

Evaluation of skin permeation of β-blockers for topical drug delivery

PURPOSE

β-Blockers have recently become the main form of treatment of infantile hemangiomas. Due to the potential systemic adverse effects of β-blockers, topical skin treatment of the drugs is preferred. However, the effect and mechanism of dosage form pH upon skin permeation of these weak bases is not well understood. To develop an effective topical skin delivery system for the β-blockers, the present study evaluated skin permeation of β-blockers propranolol, betaxolol, timolol, and atenolol.

METHODS

Experiments were performed in side-by-side diffusion cells with human epidermal membrane (HEM) in vitro to determine the effect of donor solution pH upon the permeation of the β-blockers across HEM.

RESULTS

The apparent permeability coefficients of HEM for the β-blockers increased with their lipophilicity, suggesting the HEM lipoidal pathway as the main permeation mechanism of the β-blockers. The pH in the donor solution was a major factor influencing HEM permeation for the β-blockers with a 2- to 4-fold increase in the permeability coefficient per pH unit increase. This permeability versus pH relationship was found to deviate from theoretical predictions, possibly due to the effective stratum corneum pH being different from the pH in the donor solution.

CONCLUSIONS

The present results suggest the possibility of topical treatment of hemangioma using β-blockers.

The effect of permeation enhancers on the viscosity and the release profile of transdermal hydroxypropyl methylcellulose gel formulations containing diltiazem HCl

BACKGROUND AND METHOD

The objective of this study was to characterize the release of Diltiazem HCl (DTM HCl) from hydroxypropyl methylcellulose gels containing the following permeation enhancers at a 0.5% (w/w): sodium lauryl sulfate, dimethyl sulfoxide (DMSO), polysorbate 80, propylene glycol, N-methylpyrrolidone (NMP), fatty acids (oleic acid, caprylic acid, and myristic acid), and isopropyl myristate (IPM). The enhancers' effects on the gel's viscosity were also investigated.

RESULTS

The novel findings of this study were the following: (i) polysorbate 80 was used for the first time as an enhancer with a hydrophilic compound in a hydrophilic carrier and it rendered the highest permeation flux (57.1 +/- 0.9 microg/cm(2)/h) compared with the rest of the enhancers, (ii) myristic acid (a 14-carbon-chain fatty acid) rendered the highest permeation flux (18.4 +/- 0.49 microg/cm(2)/h) among all fatty acids because of a decrease in the gel's viscosity, (iii) NMP (46.5 +/- 0.7 microg/cm(2)/h) and IPM (15.3 +/- 0.41 microg/cm(2)/h) increased the permeation flux from the second day onward. Both enhancers increased the gel's viscosity, (iv) sodium lauryl sulfate decreased the viscosity of the gel and the drug's permeation flux (8.1 +/- 0.21 microg/cm(2)/h) because of its binding with the drug, (v) propylene glycol decreased the permeation flux (10.2 +/- 0.32 microg/cm(2)/h) by increasing the gel viscosity, and (vi) DMSO increased the permeation flux (13.8 +/- 0.4 microg/cm(2)/h) without altering the viscosity.

CONCLUSION

These findings indicate that to formulate DTM HCl into a hydroxypropyl methylcellulose gel the enhancers of choice should be polysorbate 80, myristic acid, DMSO, NMP, and IPM or combinations thereof.

Topical drug delivery by a polymeric nanosphere gel: Formulation optimization and in vitro and in vivo skin distribution studies

Tyrosine-derived nanospheres have demonstrated potential as effective carriers for the topical delivery of lipophilic molecules. In this investigation, a gel formulation containing nanospheres was developed for effective skin application and enhanced permeation. Carbopol and HPMC hydrophilic gels were evaluated for dispersion of these nanospheres. Sparingly water soluble diclofenac sodium (DS) and lipophilic Nile Red were used as model compounds. DS was used to determine the optimum polymer type, viscosity and release properties of the gel while fluorescent Nile Red was used in in vitro and in vivo skin distribution studies. In addition, the effect of a penetration enhancer, Azone, on the skin delivery was investigated. Dispersion of Nile Red-loaded nanospheres in 1% w/v HPMC gel produced a uniform and stable dispersion with suitable rheological properties for topical application, without any short-term cellular toxicity or tissue irritation. In vitro permeation studies using human cadaver skin revealed that the deposition of Nile Red via the nanosphere gel in the upper and lower dermis was 1.4 and 1.8 fold higher, respectively, than the amount of Nile Red deposited via an aqueous nanosphere formulation. In vivo, the HPMC gel containing Nile Red-loaded nanospheres significantly enhanced (1.4 fold) the permeation of Nile Red to the porcine stratum corneum/epidermis compared to the aqueous Nile Red-loaded nanospheres. An additional increase (1.4 fold) of Nile Red deposition in porcine stratum corneum/epidermis was achieved by incorporation of Azone (0.2M) into the nanosphere gel formulation. Therefore, tyrosine-derived nanospheres dispersed in gels offer promise for the topical delivery of lipophilic drugs and personal care agents to skin for treatment of cancers, psoriasis, eczema, and microbial infections.