Abstract. Yam (Dioscorea esculenta) starch was modified by carboxymethylation. The effect of reaction parameters, amount of sodium hydroxide (NaOH), amount of sodium monochloroacetate (SMCA), and reaction time on the degree of substitution (DS) of carboxymethyl yam starch (CMS), was studied using the Box-Behnken experimental design. Physicochemical and potency to be a tablet disintegrant of CMS were evaluated. CMS with DS in the range of 0.08-0.19 were obtained. The results from regression analysis indicated that the most important factor in controlling DS was the amount of NaOH followed by SMCA content and reaction time. However, high concentration of NaOH and SMCA lowered the DS. The optimal conditions to achieve the highest DS (0.19) were found to be at molar ratios of NaOH and SMCA to anhydroglucose unit of 1.80 and 2.35, respectively, and with the reaction time of 4.8 h. The swelling power and viscosity of CMS increased with an increase in the degree of modification. CMS showed satisfying tablet disintegrant properties. The tablets containing 1.0-4.0 % CMS disintegrated faster than 5 min. Hence carboxymethyl yam starch can be used as an excellent tablet disintegrant in low concentration.

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Generally, drug release from controlled release oral dosage forms would be affected by pH, gastrointestinal motility and the presence of food in gastrointestinal tract. Osmotic controlled-release oral delivery system, which utilizes osmotic pressure as the driving force for controlled delivery of active agent(s), however is not influenced by these factors, and it is possible to predict the release characteristics from the known properties of the drug and the dosage form [1][2][3] . The simplest design of elementary osmotic pump consists of an osmotic core (comprising a drug with or without an osmogent) coated with a semi-permeable membrane. After coming in contact with the gastrointestinal fluids [4,5] , it absorbs water at a rate determined by the fluid permeability of the membrane and osmotic pressure of core formulation. This osmotic imbibitions of water results in the formation of a saturated solution of drug within the core, which is dispensed at a controlled rate from the delivery orifice in the membrane [6,7] . In addition, there are numerous factors that affect the drug release from osmotic pumps (i.e. drug solubility, osmotic pressure, delivery orifice and types or characteristics of the film). The membrane permeability is one of the important factors that need to be concerned when designing the system because the delivery of drug from oral osmotic systems is controlled by the influx of solvent across the semipermeable membrane, which in turn carries the agent to the outside environment [2,8] . Water influx into basic osmotic pump system can be described by the following Eqn. [3] , dv/dt = A×Lp×(σ∆π-∆P)/h, where dv/dt is water influx, A and h are the film area and thickness, respectively; Lp is mechanical

The objective of this research aimed to 1. formulate chewable toothpaste tablets containing mangosteen rind extract, 2. compare the suitable filler between lactose anhydrous and mannitol that adsorbs mangosteen rind extract by flowability and appearance indicators, 3. study the effect of type and amounts of foaming agents on stability of foam that leads to appropriate formulation, and 4. study market feasibility of chewable toothpaste tablets containing mangosteen rind extract. Survey method and self-administered questionnaire was used for data collection both before and after formulation in capital district of Nakhon Pathom. Thirty participants were selected and categorized into five groups which are tourists, dental patients, pharmacy students at Silpakorn University, office workers and dentists. After data collection is done, it was analyzed by using descriptive statistics. Results showed that mannitol is an appropriate adsorbent. It showed proper color and appearance as well as good flowability of extract. Cocamidopropyl betaine was selected as foaming agent. According to the survey, participants are interested in product. In addition, some dental specialists suggested to add fluoride. Overall, this product is interested and accepted among participants. Therefore, consumers are likely to buy chewable toothpaste tablet containing mangosteen rind extract.