Pt19 method of preparation of emulsion for external use
Method of preparation of emulsion for external useSoap emulsion fatty acid oil phase mix alkali aqueous phaseWaxy solid emulsion melt wax before mixing maintain similar temperature before mixing
For rectal useSuppositories : solid preparations for rectal useEnemas : liquid preparation for rectal use Starch mucilage, sodium carboxymethylcellulose used as an emollient and suspending/emulsifying agent
Colligative propertiesProperties depend on the number of solute particles in solution • osmotic pressure • vapor-pressure lowering • boiling-point elevation • freezing-point depression
Osmotic pressureDefinition of osmosisthe diffusion of solvent through a semi-permeablemembrane from the solution of lower solute concentrationto the solution of higher solute concentrationOsmotic pressure The force causes osmosis
Isotonic solutionTwo solutions separated by semi-permeablemembrane are in osmotic equilibrium
Pharmaceutical preparations requiring isotonicityInjections subcutaneous injection not necessary intramuscular injection must be isotonic intravenous injection isotonic in large volume intrathecal injection (subarachnoid/subdural space) strict isotonicityEye drops not necessaryNasal drop not necessaryIsotonicity reduces pain on injection or administration
Adjustment of isotonicity• freezing point depression• molar concentration• sodium chloride equivalents
Freezing point depressionFreezing point of blood plasma and tears : － 0.52 ℃Solution which freezes at － 0.52 ℃ have the sameosmotic pressure as body fluids. 0.52 － a W= b W: concentration in grams per 100mL (w/v %) of adjusting substance in the final solution a: freezing point depression of the unadjusted hypo-osmotic solution b: freezing point depression produced by 1% w/v of adjusting substance
Molar concentration0.28 mol/L solution is isotonic with blood plasma andtears 0.28 x M W= n W : concentration (g/L) of solution M : molecular weight of the substance n : number of ions formed from the substance
Sodium chloride equivalentsThe mass (gram) of NaCl that has an effect on freezing pointdepression equivalent to that produced by 1 g of substance 0.9 w/v % of NaCl solution is isotonic with blood serum and tears. W = 0.9 － a x c W : percentage of NaCl required for adjustment a: NaCl equivalent of substance c : percentage of substance solution
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