We noticed that in many formulas, Lactose and Avicel are used together, not necessarily in their co-processed form, I mean their simple individual mixing, what effect do they have on each other and on the formula as a whole when used together?
lactose may increase dissolution of some drugs. Unfortunately, it can increase disintegration time especially in form of monohydrate. So, Avicel is added to make balance. Avicel is diluent but it has disintegration properties too
Thanks Asmaa Abdelaziz Mohamed so much. Is there a reference mentioning this or elaborating more on this, please?
Asmaa Abdelaziz Mohamed lactose and avicel (MCC) also have slightly different compression profiles. Lactose is a moderately hard brittle material whereas avicel is a soft ductile material. Depending on the compression profile of your active ingredient these materials are usually combined at optimum quantities in a formulation for the best compression as well as target dissolution profile as Marwa Abd El Kader Zaater suggests above. I hope this helps.
Avicel has plastic fracture with low yield pressure while lactose has brittle fracture with higher yield pressure. This means at low compression pressure avicel gives stronger tablets as compared to lactose. Combination of both excipients will reduce the slope of tablet hardness vs compression graph. This will mitigate the sensitivity of tablet compression pressure on tablet hardness and hence dissolution.
Avicel is lubricant sensitive while lactose is not. Adding lactose will mitigate this.
Avicel has low bulk density while lactose has higher bulk density. Using Avicel alone might cause in inconsistent die filling at higher press speed due low bulk density. Adding lactose will mitigate this.
Avicel looses compressibility on prolonged exposure to water during wet granulation, while lactose does not. Therefore, lactose will mitigate the risk.
Overall, having both is like having best of both worlds. Marwa Abd El Kader Zaater
Both lactose and microcrystalline cellulose are combined for the following complementary effects,
Lactose exhibits brittle fracture whereas Microcrystalline Cellulose exhibits Plastic Deformation. When combined there is a balance of Cohesion and Adhesion.
Lactose exhibits erosion type disintegration pattern whereas Microcrystalline Cellulose exhibits bursting type disintegration pattern. Both are combined to overcome the long DT of Lactose as well as to prevent the sticking and heap formation tendency in dissolution testing.
In Wet granulation process, fluid uptake is minimal for Lactose whereas higher for Microcrystalline Cellulose. For effective granulation without local wetting and for achieving homogenous binder distribution, Lactose and Microcrystalline Cellulose were combined.
In Dry granulation process (Slugging / Roller Compaction), multiple compaction cycle is not possible with only Lactose in formula and must be augmented with Microcrystalline Cellulose to achieve densification, flow and compressibility.
From shelf life aspect, bone drying phenomena of Lactose causes retardation of dissolution and disintegration with composition having Lactose as a major diluent and can be solved and balanced with Microcrystalline Cellulose.
Ofcourse because of Lactose intolerance, diluent amount in formulation is balanced with Microcrystalline Cellulose.
Reason behind MCC and Lactose use in combination:-
1 Lactose show brittle fracture whereas MCC show Plastic Deformation during compression cycle. When combined use there is optimum hardness at low compression force. no need to increase higher compression force. we can avoid no of issue eg. impurity generation, punch damage, safety.
2.In Wet granulation, water holding nature of MCC is higher as compared to Lactose. when use in combination give optimum granules:fine ratio.
DT.
3. Lactose single diluent for dry granulation, slugging not produce optimum DT, Flow, Optimum Granules:fine ratio, use in combination give proper flow, optimum DT, Dissolution, granules:fine ratio.
4.Lactose is water soluble and MCC is water insoluble, when use in combination give optimum DT, and Dissolution.
A combination of MCC and lactose produce a synergic effect in compressibility because of the different deformation characteristics of the two materials.
Packiaraj Jeyachandran Manohari Can you please cite a reference for the insight you provided in answer. A journal reference will be much helpful.
Subhradip Roychowdhury
you can find the relevance in the following,
1) individual monograph of lactose and microcrystalline cellulose in Handbook of Pharmaceutical Excipients.
2) google search - lactose brittle fracture
3) google search - microcrystalline cellulose plastic deformation
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