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|The Hokunalin® Tape jointly developed in 1988 by Abbott Japan Co., Ltd and Nitto Denko was the world's first transdermal patch for treatment of asthma. The adhesive layer of the tape contains tulobuterol, a drug that dilates the bronchial tubes making it easier for asthma sufferers to breathe. When the patch is applied to the skin, the drug penetrates the skin and is absorbed into the blood stream through the capillaries to flow throughout the body. This is in effect the same as using an injection, but without requiring the use of a needle.
Unlike conventional oral and inhaled formulations, Hokunalin® Tape has the advantage of being able to appropriately control the concentration of the drug in the body. This means that users can control asthma attacks, which frequently occur in the early morning, and that the burden on caregivers is also greatly reduced.
The development of these patches, however, took 11 years and was full of challenges.
|Designing transdermal patches is one area in which Nitto Denko has a great deal of expertise. By 1983 we had already developed a transdermal patch for preventing the onset of angina.
With conventional transdermal formulations, drugs were continuously in the body for long periods of time. The developers wanted to develop a more advanced product that was able to deliver the required drug dosage at the right time for use in the treatment of asthma.
In many cases, asthma attacks occur at set times, such as in the early morning. If a drug delivery system could be developed that was able to deliver the optimum amount of medication at that time (a smart drug delivery system), then it would be possible to dramatically increase the quality of life of asthma sufferers.
In order to realize this goal, however, it is necessary to achieve precision control of drug release speed. This proved to be extremely difficult.
|Drug release speed is determined by the complex relationships between the type of adhesive used, the thickness of the adhesive coating, and the content and concentration of drug contained in the adhesive. Moreover, the type of adhesive that can be used in medical applications is also limited, which means that inevitably it is necessary to control release speed using drug content and concentration.
In the absence of any revolutionary way of solving this problem, it was a matter of making samples with various combinations in a process of trial and error. Although computer simulations can now be used for parts of this process, at that particular time there was no such convenience. It was a case of trying every combination and investigating each individual possibility.
Eventually, as a result of many years of painstaking hard work, this goal was achieved by utilizing a mechanism whereby some of the drug in the adhesive was maintained in a crystalline state while the rest was kept in a dissolved state. This proprietary technology was subsequently applied in the manufacture of other adhesive tapes.
In order to commercialize this product, however, the company first had to develop advanced processing technology. In the transdermal patch manufacturing process, it was necessary to maintain the thickness of the adhesive layer at µ20 (0.02mm). Because the product was to be used in medical applications there could be no variation in quality and at the time of manufacture it was necessary to control tape thickness to within ±2µm (0.002mm).
It is no exaggeration to say that precision coating technology is the real secret behind the successfully commercialization of this product.
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