Bioequivalence of marketed transdermal delivery systems for tulobuterol

Generic selection criteria for safety and patient benefit [Ⅻ]: Comparing the physicochemical and pharmaceutical properties of brand-name and generic tulobuterol tape

Physicochemical properties (drug release, peel strength, adhesion, and stiffness) of Hokunalin® Tape (Hokunalin) and 13 generic transdermal bronchodilator patches containing tulobuterol were characterized and evaluated for comparison. Drug-release studies evaluating sustained release behavior demonstrated better performance by the drug Hokunalin, than the generics MED, YP, Sawai, and Teikoku. Hokunalin yield a 16.2% release 1 hour after initiation, 30.1% at 3 hours, 50.0% at 8 hours. In comparison, the generics MED, YP, Sawai, and Teikoku showed an intermediate release behavior to that of Hokunalin, with more than 80% release after 8 hours. A 90-degree peel adhesion test for tape peel strength demonstrated that the generic MED (4.99 N), YP (3.26 N), Sawai (4.17 N), and Teikoku (4.37 N) tapes yielded significantly higher values compared to Hokunalin (2.66 N). Probe tack tests, evaluating adhesive strength, yielded significantly higher values for the generics HMT (4.89 N)and Towa (4.25 N) compared to Hokunalin (3.66 N). Furthermore, for the stiffness-softness test, a significantly higher value was obtained for each generic yielded compared to Hokunalin (3.7-degree). These factors are important components of product qualities that affect treatment efficacy, including "ease of application" and other usability factors.

[Effect of Storage of Tulobuterol Tapes after Package Opening and Liner Peeling on Their Formulation Properties]

Although tulobuterol tape is provided to patients in an inner package, information regarding the stability of the tape after opening the packaging may be requested by patients. This study was performed to generate underlying data on the storage stability after package opening or liner peeling with package opening. Tulobuterol tapes were stored at 25℃, 60% relative humidity (RH); 40℃, 75%RH; or in a refrigerator (2-4℃, 10-30%RH) for 1 day or 3 days. In a peel adhesive strength test after package opening, storage at 25℃, 60%RH had a low effect on the adhesive strength of the tape. Storage after liner peeling with package opening resulted in variable adhesive strength of the tape. Regarding drug release properties, for storage after package opening, the f2 values of tapes stored in the three different conditions were over 50, except for tapes stored at 25℃, 60%RH for 3 days. For the tapes stored at 25℃, 60%RH or 40℃, 75%RH after liner peeling with package opening, the release rate and the ratio of drug released at 24 h may be decreased because the drug content decreased due to drug sublimation. This study suggested that tulobuterol tapes can be stored after package opening at 25℃, 60%RH for 1 d.

Enhancement of Skin Permeation of a Hydrophilic Drug from Acryl-Based Pressure-Sensitive Adhesive Tape

PURPOSE

Penetration enhancers are necessary to overcome a formidable barrier function of the stratum corneum in the development of topical formulations. Recently, non-lamella liquid crystal (NLLC)-forming lipids such as glycerol monooleate and phytantriol (PHY) are gaining increasing attention as a novel skin permeation enhancer. In the present study, fluorescein sodium (FL-Na) was used as a model hydrophilic drug, and acryl-base pressure-sensitive adhesive (PSA) tape containing NLLC forming lipids, mono-O-(5,9,13-trimethyl-4-tetradecenyl) glycerol ester (MGE) or PHY, was prepared to enhance drug permeation through the skin.

METHODS

A PSA patch containing FL-Na was prepared by mixing FL-Na entrapped in NLLC and acrylic polymer. FL permeation through excised hairless rat skin, and also human skin, was investigated. Changes in lipid structure, folding/unfolding state of keratin in the stratum corneum, and penetration of MGE into the stratum corneum were investigated using confocal Raman microscopy.

RESULTS

Enhanced FL permeation was observed by the application of a PSA patch containing MGE and PHY. Especially, dramatically enhancement effect was confirmed by 15% of MGE contained formulation. Penetration of MGE provided diminished orthorhombic crystal structure and a peak shift of the aliphatic CH₃ vibration of keratin chains toward lower wavenumbers.

CONCLUSION

The present results suggested that the formulation development by adding MGE may be useful for improving the skin permeation of mal-permeable drugs such as hydrophilic drugs.

Skin permeability of tulobuterol in two transdermal formulations and their followability

Various generic transdermal formulations of tulobuterol containing rubber and acrylate base polymers are commercially available in Japan. However, none of the formulations have been compared directly with respect to the skin permeability of tulobuterol and to their follow ability. Tulobuterol Tape Sawai of rubber base and Tulobuterol Tape NP of acrylate base were used to conduct the in vitro 24-hour skin permeability test of tulobuterol at receiver solution temperatures of 32°C, 37°C, and 40°C. Furthermore, the followability of these tapes were examined by measuring the depth of the pores that were formed in their adhesive layer. Consequently, the maximum flux of tulobuterol was greater for Tulobuterol Tape NP. Arrhenius plot analysis revealed that Tulobuterol Tape Sawai was more sensitive to skin surface temperature compared with Tulobuterol Tape NP. Skin abrasion had a greater effect on the skin permeability of tulobuterol in Tulobuterol Tape Sawai than in Tulobuterol Tape NP. Followability was greater for Tulobuterol Tape NP than for Tulobuterol Tape Sawai. These results suggest that a transdermal formulation of acrylate base is preferable to that with a rubber base when skin surface temperature varies or when the skin is abraded. In clinical settings, therefore, a formulation of acrylate base is preferable to a formulation of rubber base when skin surface temperature varies or when the skin is abraded. The formulation needs to be applied to the skin of less asperity for the achievement of better transdermal absorption of tulobuterol.

Evaluation of the predicted time-concentration profile of serum tulobuterol in human after transdermal application

We proposed an in vitro/in vivo/in silico method for evaluating the clinical performance of matrix type transdermal therapeutic systems (TTSs). This method is based on the following four approaches: (1) drug release experiment, (2) in vitro penetration experiment using excised hairless mouse skin, (3) clinical pharmacokinetic study, and (4) mathematical model for evaluating the pharmacokinetic profile. The tulobuterol TTS was used as an example of a matrix type TTS in this study. The drug diffusion coefficient in the matrix device was calculated from the result of the release experiment. The drug diffusion coefficient and the partition coefficient in the skin were calculated from the results of in vitro skin penetration experiments where hairless mice and rats were used. Those parameters were used as substitutes of human. Further, these parameters were used for solving the governing partial differential equation on skin penetration. The time profiles of the serum concentration in human after applying the tulobuterol TTS were predicted and compared with the clinical data. The predicted profiles obtained from the data of hairless mice reproduced the influence of drug depletion adequately and well agreed with the clinical data, while those from the data of rats differed clearly in the initial rise. This method is useful for prediction of pharmacokinetic profiles of TTSs.

Transdermal tulobuterol patch, a long-actingβ(2)-agonist

Tulobuterol patch (HokunalinTM Tape), which contains a β(2)-adrenergic agonist, is the first bronchodilator to be available as a transdermal patch. This drug delivery system ensures that the time at which the peak drug concentration in the blood is reached coincides with the morning dip in respiratory function. The use of the patch also prevents excessive increase in blood drug concentrations, thereby reducing the incidence of systemic adverse reactions. Since 1998, when it was first approved in Japan and worldwide, the tulobuterol patch has been used widely in the treatment of bronchial asthma and chronic obstructive pulmonary disease (COPD), and evidence collected since it was approved has confirmed its clinical efficacy and safety. Because the patch is easy to use and requires only once-daily application, treatment adherence of patients using the patch is good. In this article, we discuss the rationale behind the development of the tulobuterol patch, evaluate data on its clinical efficacy and safety in the treatment of asthma and COPD, and examine the treatment adherence in individuals using the patch.

[Model analysis of tulobuterol patch formulations to explain the influence of drug release rate and transdermal transfer rate on the plasma concentration profile]

The purpose of this study was to compare the transdermal transfer profiles of brand and generic tulobuterol patch formulations and to evaluate possible changes of in vivo kinetics resulting from increased transdermal transfer by means of pharmacokinetic analysis using reported in vitro drug release rate data and plasma drug concentration profiles. On the assumption that the transdermal transfer rate constant (k2) would be constant (independent of formulation), the drug release rate constant from patch formulation (k1) was predicted to be almost equal to the k2 value (k1≈k2) in the brand formulation, but 2- to 4-fold higher than the k2 value (k1>k2) in the two generic formulations. Under normal conditions, there would be no marked difference in the plasma concentration profiles among the formulations. However, under conditions where transdermal transfer is increased (that is, higher k2), the plasma tulobuterol concentration was predicted to increase more rapidly, with higher C(max), and then to decrease more rapidly in the elimination phase after applying the generic formulations compared with the brand formulation. These different behaviors would be seen because the transdermal transfer of the generic formulations would be affected by k2, whereas k1 is still rate-determining for the brand formulation. These results suggest that bronchial asthma patients with risk factors for impaired skin barrier function, including atopic dermatitis, long-term treatment with steroids, and advanced age, should be carefully monitored for reduced treatment efficacy or adverse drug reactions after application of rapid-release generic tulobuterol patch formulations.

Comparative study of skin permeation profiles between brand and generic tulobuterol patches

Tulobuterol patches are long-acting bronchodilators for percutaneous absorption including the β(2)-adrenoreceptor agonist tulobuterol, as a main ingredient, used for long-term management of pediatric asthma. Since patients who have pediatric asthma often also have atopic dermatitis in which the skin barrier is impaired, we compared the skin penetration profiles of the brand and generic patches using a skin barrier-impaired rat model. Skin penetration was significantly (p<0.001) higher in the generic patches compared with the brand patch, suggesting that it is important to understand the pharmaceutical properties of available products by giving careful consideration not only to the patient's asthma control but also to their skin condition before using tulobuterol patches.

Effect of environmental temperature on transdermal drug penetration

The effect of environmental temperature on the penetration from matrix-type transdermal patch of non-steroidal anti-inflammatory drugs (NSAIDs) as model drugs was investigated using in vitro and in silico experiment. The patch was applied on the stratum corneum (SC) side of the skin. The dermal side of the skin was mounted on a diffusion cell. The donor compartment of the diffusion cell was filled with distilled water. The donor temperature was set at 2, 25, 37, and 47 °C, respectively. The receptor compartment was kept at 37 °C and filled with phosphate buffer solution during the experiment. The permeation of the drugs from patch increased with increasing the donor temperature. The rate of permeation increased exponentially with increasing skin surface temperature. The diffusion coefficient in the skin remained almost constant, while the skin surface concentration was correlated with the skin surface temperature. The plasma concentrations in human were simulated by SKIN-CAD(®) together with the in vitro penetration experiment. The plasma concentration quickly changed with varying the environment temperature.

Polymeric matrix system for prolonged delivery of tramadol hydrochloride, part I: physicochemical evaluation

Management of moderate or severe chronic pain conditions is the burden of clinicians dealing with patients trying to improve their quality of life and diminish their suffering. Although not a new opioid, tramadol has been recently rediscovered and widely used; this may be due to its favorable chronic safety and dependence profiles together with its high potency. Tramadol is a centrally acting analgesic with half-life of approximately 6 h; therefore, it requires frequent dosing. It is freely soluble in water; hence, judicious selection of retarding formulations is necessary. The current study is focused on the innovation of a novel, simple, monolayer, easy-to-use, cost-effective, and aesthetically acceptable bioadhesive transdermal delivery system overcoming the defects of the conventional "patch" as carrier system for tramadol, ensuring its adequate delivery, along with the physicochemical evaluation of the designed formulations. Monolithic tramadol matrix films of chitosan, different types of Eudragit, and binary mixtures of both were prepared. As a single-polymer film, chitosan film showed best properties except for somewhat high moisture uptake capacity, insufficient strength and rapid release, and permeation. Polymer blends were monitored in order to optimize both properties and performance. Promising results were obtained, with chitosan-Eudragit NE30D (1:1) film showing the most desirable combined, sufficiently rapid as well as prolonged release and permeation profiles along with satisfactory organoleptic and physicochemical properties.

Transdermal delivery of praziquantel: effects of solvents on permeation across rabbit skin

To explore a new method for the transdermal delivery of praziquantel (PZQ), the effects of solvents on permeation across rabbit skin were investigated. The solubility of PZQ in five different solvents, ethylene glycol monophenyl ether (EGPE), 1,4-dioxane, tetrahydrofuran, dimethyl sulfoxide, and oleic acid, were measured with a UV-Vis spectrophotometer. The determination of the n-octanol/water partition coefficient of PZQ in the five different solutions and assay of serum concentration following PZQ transdermal administration in rabbits were performed using HPLC. The results indicated that the transdermal absorption of the drug was related to the partition coefficient and lipophilic characteristics of the solvent. The optimal solvent for PZQ transdermal delivery was EGPE in our protocol. The solubility of PZQ in EGPE is >400 mg/ml, and the apparent partition coefficient of PZQ in the solution is 0.895 (log P value). After transdermal administration of PZQ in EGPE solution, the bioavailability is 2.85-fold that after oral administration. The serum drug concentration was maintained at 4.0 mug/ml over 4 h, which is sufficient for the treatment of schistosomiasis. At the same time, no apparent side effects were found on the skin. EGPE may thus be a promising vehicle for the transdermal delivery of PZQ in the future.