Improvement by super disintegrants of the properties of tablets containing lactose, prepared by wet granulation.

The crushing strength, disintegration and dissolution properties of tablets, made by wet granulation with lactose as filter, gelatin as binder, potato starch as disintegrant and magnesium stearate as lubricant can be markedly improved when the potato starch (20%) is replaced by a much lower concentration (4%) of an insoluble super disintegrant, such as sodium starch glycolate (Primojel) or crospovidone (Polyplasdone XL). The incorporation of partially water soluble super disintegrants such as low-substituted sodium carboxymethylcellulose (Nymcel, ZSD 16), causing a viscous barrier in the tablets when containing water, is shown to be deleterious for both tablet disintegration and drug release. In contrast to potato starch, the position of the super disintegrants (intragranular, extragranular or equally distributed) had hardly any effect on the tablet properties. The improved properties of the tablets containing insoluble super disintegrants, when compared to tablets with potato starch, are the result of the use of a much lower concentration of disintegrant, but especially of the difference in effect of magnesium stearate on the disintegration capacity of the slightly swelling potato starch and the strongly swelling super disintegrants, respectively. The latter cause, even in the presence of the liquid penetration inhibiting hydrophobic magnesium stearate, a chain reaction of opening of the tablet, starting at the outside and resulting in a fast disintegration.