Rheogram or curve of Plastic flow (Bingham bodies)

Non-Newtonian Fluids

Most fluid pharmaceutical products are not simple liquids and do not follow Newton’s law of flow. These fluids are known as non-Newtonian fluids. Non-Newtonian behavior is typically seen in liquid and solid heterogeneous dispersions, such as colloidal solutions, emulsions, liquid suspensions, and ointments. When non-Newtonian materials are analyzed using a rotational viscometer and the results […]

Rheograms or flow curves of Newtonian liquids.

Newtonian Fluids

Newtonian fluids are simple liquids that follow Newton’s law of direct proportionality between shear stress and shear rate. In these fluids, viscosity remains independent of both shear stress and shear rate. The viscosity of simple liquids (which include pure liquids with small molecules and solutions where both solute and solvent are small molecules) depends solely […]

The polymeric structure of sodium starch glycolate.

Sodium Starch Glycolate

Starch is a generic term for carbohydrate particles found in many plants. Starch grains swell in contact with water, and this appears to be an important property that relates to their use as tablet disintegrants. Sodium starch glycolate is the sodium salt of cross-linked carboxymethylated starch (chemically modified starches). When viewed under the microscope it […]

Polymeric structure of Cellulose acetate phthalate

Enteric Coated Tablets

Enteric coated tablets, also called gastro-resistant tablets, have delayed-release features. They are designed to pass unchanged through the stomach to the intestines, where the tablets are insoluble at the low pH of the stomach but dissolve at the higher pH values of the intestine. Some of the most important reasons for enteric coating are: To […]

Fig. 1: The chemical structure of cellulose.

Microcrystalline Cellulose

Microcrystalline cellulose (MCC), often known as Avicel, is the most common of cellulose (Fig.1) powder used in tablet formulation. It exists in two grades, pH 101 (powder) and pH 102 (granules), and possesses good flow properties with excellent direct compression characteristics. Microcrystalline cellulose is insoluble in water and alcohol. Despite being insoluble in water, promotes […]