Sustained release dosage forms have the ability of maintaining the desired therapeutic plasma drug concentration over longer periods of time. Lower fluctuations in plasma drug concentra- tion cause less side effects, lower the need for redosing and increase the patient's adherence. Zero order release model provides drug release independent of drug concentration. Drug release takes place at a constant rate, thus making it the desired release model for sustained release dosage forms. Osmotic drug release systems can achieve zero order release kinetics independ- ent of release media characteristics.
The objective of this thesis was to develop a push-pull osmotic pump that can deliver a dose of tartrazine in eight hours with zero order release kinetics. Materials from the manufacturer Colorcon (R) were used for producing the osmotic pump. POLYOX(TM) Coagulant LEO and NaCl were used to form the push layer of the osmotic pump. POLYOX(TM) N-80 NF LEO and tartrazine were used for forming the pull layer. Opadry(R) CA was used for coating and forming the sem- ipermeable membrane.
The osmotic pump was formed by compressing a bilayer tablet on the tablet press and spray coating it in a perforated drum. Delivery orifice was formed by mechanical drilling. Dissolution testing was conducted on a reciprocating cylinder dissolution apparatus (USP III). Release me- dium with pH of 1 was used for the first two hours of dissolution, followed by six hour disso- lution in medium with pH 6.8, simulating the passage from stomach to the small intestine. This thesis focused on evaluating the impact of push-pull osmotic pump composition on release kinetics of tartrazine. The impact of the ratio of push and pull layer (2:1.3, 2:1.6 and 2:2), NaCl content in the push layer (35 % and 45 %) and the impact of the thickness of the semipermeable membrane (8 mg/cm2, 10 mg/cm2 and 12 mg/cm2) on the release kinetics of tartrazine were evaluated. Furthermore, the impact of media pH on the release kinetics was evaluated. Membrane thickness had the greatest impact on the release rate of tartrazine. The release rate of tartrazine was inversely proportional to membrane thickness. Higher the amount of NaCl in the push layer, slower the release rate of tartrazine. Higher amount of push layer in the tablet resulted in faster release rate of tartrazine, but the impact was smaller than the impact of mem- brane thickness. Change of media pH during release did not affect the release kinetics of tartra- zine.
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