The Deryagin rule is a rule developed by the chemist B.V. Deryagin regarding the technology of many dosage forms.
The wording of the rule:
To obtain finely ground medicinal substance during its dispersion, it is recommended to add a solvent in half the amount of the mass of ground medicinal substance. [one]
Rule explanation
Particles of a drug substance have cracks (Griffith cracks) into which liquid penetrates. The liquid exerts a proppant pressure on the particle, which exceeds the compressive forces, which contributes to grinding. If the ground substance is swellable, then it is thoroughly ground in a dry form and only then is the liquid added. After grinding the drug substance, a stirring technique is used to fractionate the particles. Wrapping consists in the fact that when a solid substance is mixed with a liquid 10–20 times larger than its mass, small particles are suspended and large particles settle to the bottom. This effect is explained by different sedimentation rates of particles of different sizes ( Stokes law). The suspension of the finest particles is poured off, and the precipitate is re-crushed and agitated with a new portion of liquid until the entire precipitate passes into a thin suspension. [2] [3]
Technology Application
For example, a suspension recipe :
Rp .: Amyli
Bismuthi subnitratis ana 3.0
Aquae destillatae 200 ml
MDS Wipe Facial Skin
The value of the recipe: 200 ml of purified water is measured in a stand. 3 g of starch and 3 g of basic bismuth nitrate with 3 ml of water (according to Deryagin's rule) are crushed in a mortar , then 60–90 ml of water is added, the mixture is stirred and left for several minutes. Carefully pour the fine suspension from the precipitate into the vial . The wet sediment is additionally ground with a pestle , mixed with a new portion of water, drained. Grinding and stirring is repeated until all large particles have turned into a thin suspension .
Notes
- ↑ Sinev D.N., Marchenko L.G., Sineva T.D. Reference manual for pharmacy technology of drugs. 2nd ed., Revised. and add. - St. Petersburg: Publishing House of SPKhFA, Nevsky Dialect, 2001. - 316 p.
- ↑ Nikolaev L.A. Pharmacology. 2nd ed., Rev. and add. - Minsk: Higher School, 1988.
- ↑ Bobylev R.V., Gryadunova G.P., Ivanova L.A. et al. Technology of dosage forms. T. 2. - M .: "Medicine", 1991.