Compressed tablets are the most popular dosage form in use today. About two-thirds of all prescriptions are dispensed as solid dosage forms and half of these are compressed tablets. What may surprise many people is that nearly 99.9 percent of most prescription tablets are actually filler. The active ingredient is usually just one thousandth of a pill, so has to be mixed with other ingredients to bulk it out to pill size to make the medicine big enough to pick up and swallow. Now researchers are looking at a fundamental shift in the way pills are produced which promises to create safer and faster-acting medicines – "printing" pills to order.
GlaxoSmithKline (GSK) has developed a way of printing active pharmaceutical ingredients onto tablets. Currently the process can only be applied to just 0.5 percent of all medicines used in tablet form, but a collaboration between GSK, the University of Leeds and Durham University hopes to see this increase to 40 percent.
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"Some active ingredients can be dissolved in a liquid, which then behaves like normal ink, so then the process is fairly straightforward," explains Dr Nik Kapur from the University of Leeds Faculty of Engineering. "However, when you're working with active ingredients that don't dissolve, the particles of the drug are suspended in the liquid, which creates very different properties and challenges for use within a printing system. For some tablets, you may also need higher concentrations of active ingredients to create the right dose, and this will affect how the liquid behaves."
A medicine droplet is 20 times larger than an ink droplet in a standard ink-jet system, so the challenges facing the researchers include the numbers of drops that each tablet can hold, and how to increase the level of active ingredient in each drop. The research will also look at the properties and behavior of the suspension, the shape and size of the printing nozzle and ways to pump the suspension through the printing equipment.
Drugs produced in this way would be faster acting. With the active ingredient on the pill's surface, it would no longer need to be broken down by the digestive system before the drug can enter the bloodstream. Ultimately it would also be possible to print several drugs onto one pill, reducing the number of tablets to be swallowed by patients on multiple medicines.
Such a system would also see an end to the one-size-fits-all process now used by medicine manufacturers. Currently, ensuring each tablet contains the correct dose relies on statistically checking samples from each batch of pills post-production. Printing active ingredients onto pre-formed tablets would speed up and improve quality control, as each tablet contains exactly the correct dose for the patient.
The new system would therefore both speed up production and provide a greater quality assurance and consistency of dosage than are currently possible under even the highest pharmaceutical standards. With some of the current quality assurance procedures rendered unnecessary, new drugs would also reach patients much faster.
The system could revolutionize a process which has remained largely unchanged for over a thousand years. The first documented manufacture of pills goes back to Egyptian times, when active medicinal ingredients were rolled in bread or clay, but the earliest reference to a tablet - a compressed pill - is found in tenth century Arabic medical literature. The process had little changed when the first patent for tablets was applied for in 1843. First produced in small doses by pharmacists, mass production still uses the same process, but with much advanced technology and quality assurance.