There are several ways in which drug delivery to body is being achieved. One of the most important methods is via the oral route. Administration of oral drugs has its merits and demerits. An important merits is that which relates to the 'ability of patient to use it anytime, anywhere' while the major demerit is non-compliance with the usage of those drugs that are not sweet to taste. Drug taste is a significant consideration to achieving a full compliance hence health care administrator or provider must take note of such factor during prescription. In order to provide achieve full compliance, better alternatives with palatable tastes should be provided especially if available. It is important in preparation of dosage form for pediatric, geriatric or non-cooperative patients when managing them. The taste masking of drugs is an approach to achieving an acceptable and palatable taste for patients.
In recent times, taste masking has come to be the in-thing in drug industry. The technology is being explored by many pharmaceutical manufacturing companies. This taste masking technology has been used to cover the bitterness of active pharmaceutical ingredients (APIs) via orally disintegrating tablets (ODTs) platforms and thin film platforms in drug production (McLaughlin, Banbury, & Crowley, 2009). The highly promising ODT platforms used with different masking techniques to manufacture oral solid dosage form are drug delivery approaches that have helped the pharmaceutical companies solve the problem of bitter taste in solid drugs. Innovation, enhanced clinical effectiveness and improved compliance are some of the benefits of this approach in drug production. ODTs are solid drugs that are made to disintegrate in saliva within seconds when place in tongue. This change allows the active medicinal ingredients to be released quickly. In getting this done, various techniques have been formulated. Those major technologies are lyophilized tablets, compressed tablets and others (molded tablets, spray-dried powders and sugar floss) (McLaughlin, Banbury, & Crowley, 2009). It can be classified as three major groups which include; direct compression, freeze drying and molding (McLaughlin, Banbury, & Crowley, 2009). Direct compression uses more of conventional equipment and materials hence helping to minimize the cost of production while the freeze-drying technique make use of techniques that high cost of equipment and processing cost. Molded technique is more of intermediate between the two extremes in terms of cost of production. However, there are other major factors that are usually considered in the production which far outweigh the importance of cost.
There are several forms of taste masking techniques, these include: flavoring and sweetening techniques, microencapsulation, ion-exchange technique, granulation, inclusion complexation, adsorption, prodrug approach, bitterness inhibitor, multiple emulsion technique, and gel formation (Sharma & Lewis, 2010). For the purpose of this discussion, microencapsulation will be the focus. This is a very important taste masking technique for ODT drugs. The principle behind this is to coat the soluble portion of API with a properly selected polymer will reduce the contact with taste buds hence masking the taste (Sharma & Lewis, 2010). The whole idea of this masking with a selected agent is to create a form of barrier between the drug particles and taste buds. The merits of this technique is that the taste masking can easily be achieved with desirable fast or controlled drug release, bitter liquids may be coated to achieve a solid state, and the coated bitter particles can adapt to a wide variety of dosage forms.
The fact that ODTs dissolve fast in the oral cavity and get in contact with the taste buds easily, bitter APIs needs to be separated from the taste buds to improve patient acceptance and compliance. A form of microencapsulation known as Coacervation or phase separation techniques is a form of taste masking technique that make use polymeric membrane that are deposited on drug particles (Sharma & Lewis, 2010). This deposition is done in a liquid phase. The process helps forms microcapsules that allow delayed or controlled release of the active components apart from achieving the taste masking role. An average size for a single microcapsule is about 0.2-0.8mm (Fu et al, 2004). A major example of drugs formulated with this technique is pirenzepine HCl or oxybutynin HCl (Fu et al, 2004)
The process of Coacervation involves three main steps. Those steps are: formation of three immiscible chemical phases, deposition of liquid polymeric wall material and coat hardening. Step1 involves formation of immiscible phases entailing dispersion of drug into a vessel filled with solvent and the solid coating polymer. This is then followed by stirring of the drug to create three different phases. Step 2 entails heating up of the mixtures with the aim of dissolving the polymer and subsequent deposition of the polymer of the drugs particles. This process is accomplished by controlled physical mixing and cooling of the liquids. The last step entails making the drug to be rigid by polymer coating of the drug particles, and then completed coated drug particles are filtered out, washed and dried (Harmon, 2012). The diagram below illustrate the 3 stage process involve in Coacervation.
This is a common ‘over the counter’ medication in the United States. The API in the drug has an unpleasant taste. It is now being produced with different techniques of ODT and taste masking to enhance palatability of the drug. The taste of the drug is being masked by the Coacervation technique and AdvaTab technology (Eurand) is now then used to produce the ODT tablets forms of the drug. The technique for the drug production was actually designed and patented by Kyowa Hakko kogyo (Fu et al, 2004). The process is all about dispensing lubricant onto each of the tablets using a spray during the production process. The technique uses 10-30 times less hydrophilic lubricant compared to conventional tablets hence make it stronger with about 30-40 per cent. The merit of this is that those tablets are harder than conventional tablets but this strength still do not prevent liquid entry when it contacts saliva. Another positive aspect of this drug is that it can handle high drug loading and coated drug particles. No specialty packaging is required. This technique makes it easier for the packaging of Diphenhydramine HCl which could come in bottles or blister packs. The technique has now made the drug to be pleasant to taste with customized release profiles and excellent mouth-feel. The robustness associated with the tablet is as a result of the AdvaTab technique which allows the external lubrication of the tablet surface. It is easier for the ODT technique to be combined with the microcaps taste masking techniques hence making a high dose capacity drug.
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