Use of the excipient could allow the creation of tablets that are hard and resistant to damage during handling, yet still disintegrate quickly in saliva after dosing. The US patent, awarded to Roquette earlier this month, covers a solid dose form based on lactose and starch, the constituents of Starlac excipient, alongside one or more active pharmaceutical ingredients (APIs). Roquette co-developed StarLac with German company Meggle, with the French firm applying its expertise in starches alongside Meggle's skills with lactose. The resulting excipient is claimed to be unique in the marketplace as the addition of starch makes it disintegrate very quickly, despite having a good compression profile that allows the production of hard, robust tablets, with good flowability that makes processing easier. In effect, Roquette and Meggle are breaking new ground with StarLac as a diluent in so-called orodispersible (ODT) tablets - which dissolve rapidly in the mouth and are designed to make it possible to take medication without water or chewing. Xavier Duriez, senior project manager at Roquette, told in-PharmaTechnologist.com that almost all ODT products on the market use mannitol as a diluent, but that in some cases StarLac could be used as a good alternative. "StarLac is preferred for ODT and chewable formulas where palatability is a 'must'," he said, adding that the excipient provides a creamy mouthfeel that mannitol doesn't provide. According to US Patent (No. 7,201,922 ), current orodispersible formulations tend to use a number of different excipients - diluents, disintegrating agents, and lubricants for example - that can add to the complexity and cost of producing the tablets. For example, the requirement to use so-called 'super-disintegrants' in ODT formulations can make standard tablet production by direct compression difficult. The disintegrant needs to be used alongside a direct compression excipient, and this can require considerable research into different mixes to get a good result in terms of hardness and homogeneity and to avoid de-mixing, or the separation of components within the tablet.
Roquette's approach provides granules consisting of lactose and starch that have been co-dried and can be combined with the API using direct compression. The resulting tablets can be remarkably hard yet are not brittle, according to the patent. Earlier incarnations of orodispersible tablets have tended to brittleness, meaning they can start to disintegrate when removed from their packaging and handled, it notes. One formulation based on the painkiller ibuprofen found that even for very hard tablets the formulation would still dissolve within 40 seconds of being placed in the mouth. That said, the lactose/starch combination is not appropriate for use with all APIs, said Duriez, and particular attention is required when formulating it with some sensitive actives such as amino compounds. StarLac, a mixture of 85 per cent lactose and 15 per cent natural corn starch, was first introduced in 2002. Lactose is widely used as a tablet binder, while starch acts as a disintegrant. However, before the introduction of StarLac combining these two excipients required an expensive wet granulation step to avoid problems of poor flow and a tendency of segregation. Roquette also markets a brand of mannitol, Pearlitol, for use as an excipient in ODT and other dosage forms. ODT tablets are a growing sector among oral dosage forms, and are aimed at improving compliance with treatment in people who can have difficulty taking regular tablets, such as the elderly and young children. The format has been widely adopted in the US over the last five to six years, particularly to extend the patented life of established product franchises, but has taken longer to develop in Europe, according to Duriez.
The size of the market is hard to establish as it is hard to distinguish the boundaries between soft chew and ODT products, he noted.