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APRIL 2009

Stable Micro Systems, global expert in texture analysis and materials testing, has developed innovative technology to evaluate the efficacy of alginate rafts. For the first time, manufacturers can accurately and repeatably quantify the characteristics of alginate gels, which are used to treat gastro-oesophageal reflux disease (GORD) or heartburn. The new “alginate raft hook” will help them optimise the cohesiveness, buoyancy, volume and strength of these gels, so improving their efficacy.

Alginate reflux preparations are the leading remedies for GORD. They function by forming a neutral, insoluble floating gel layer (or raft) on top of stomach contents. This prevents gastric acid from rising into the oesophagus, which can damage the oesophageal mucosa and cause burning pain in the chest area. Alginate rafts, which commonly also contain antacids, provide rapid and long-lasting relief from these symptoms.

The efficacy of alginate rafts is heavily influenced by their physical properties. Formulation factors such as the types and quantities of antacids used, their ratio to the alginate dose, the acid-neutralising capability, molecular weight, concentration and viscosity can affect the formation and quality of the raft. Stable Micro Systems’ new alginate raft hook will help OTC medication producers develop effective products that retain optimal physical characteristics.

Previous raft characterisation was often based on pH levels in and below the raft, but these tests were difficult to conduct and their results lacked accuracy. The new test method, on the other hand, is simple and precise and has been adopted by the British Pharmacopoeia. The sample being examined is formed around an L-shaped stainless steel wire probe held upright in a glass beaker for a period of 30 minutes. When the raft has developed fully, the beaker is placed on the test bed of a TA.XTplus texture analyser. The wire probe is hooked onto the texture analyser’s arm and pulled vertically up through the raft at a rate of 5mm/s. The force required to pull the wire probe up through the raft is recorded as the raft strength.

This test method has been published in the International Journal of Pharmaceutics, which also outlined how to assess “resistance to reflex by extrusion”, measured by driving the raft through the orifice of a forward extrusion cell. The TA.XTplus can also be used to quantify the raft’s “resistance to reflux by rupture.” This is defined as the maximum force required to break the raft, through a 10mm diameter orifice, with a 9mm diameter cylindrical probe.

The new alginate raft hook is the latest addition to an extensive range of fixtures precision-engineered by Stable Micro Systems for the characterisation of pharmaceutical and healthcare products. The company’s instruments can evaluate characteristics such as powder flow, mucoadhesion, tablet and gel strength and granule compressibility.


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