Lubricants are the excipients that are added in the formulation to prevent sticking by reducing friction between particles and machine parts. Besides giving this effect lubricant also effect tablet disintegration and dissolution. Lubricants form a layer around granules which reduces friction. There are two types of lubricants one is hydrophobic e.g. Mg-stearate and the other is hydrophilic e.g. sodium stearyl fumarate.
Hydrophobic lubricants affect tablet disintegration and dissolution if their concentration exceeds from recommended limits or mixing time is increased, that’s why lubricants are added at the final step of blending and mixing time is held minimum e.g 3-5 min.
How It Effects?
If mixing time is increased or a higher concentration of hydrophobic lubricants is used the layer formed around granules become strong or thick and retard or slow down the penetration of water during disintegration and increase the disintegration time and hence dissolution profile is also prolonged. So lubricants should be used in optimum concentration and should be added at the end of blending and blending time should be minimum.
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