1. Method of preparation of
emulsion for external use
Soap emulsion
fatty acid  oil phase
mix
alkali  aqueous phase
Waxy solid emulsion
melt wax before mixing
maintain similar temperature before mixing

2. For rectal use
Suppositories : solid preparations for rectal use
Enemas : liquid preparation for rectal use
Starch mucilage, sodium carboxymethylcellulose
used as an emollient and
suspending/emulsifying agent

3. Colligative properties
Properties depend on the number of solute particles in solution
• osmotic pressure
• vapor-pressure lowering
• boiling-point elevation
• freezing-point depression

4. Osmotic pressure
Definition of osmosis
the diffusion of solvent through a semi-permeable
membrane from the solution of lower solute concentration
to the solution of higher solute concentration
Osmotic pressure The force causes osmosis

5. Isotonic solution
Two solutions separated by semi-permeable
membrane are in osmotic equilibrium

6. Hypotonic Hypertonic
solution solution
Lower osmotic pressure higher osmotic pressure
than blood serum than blood serum
RBC burst, haemolysis RBC shrink
irreversible reversible

7. Pharmaceutical preparations
requiring isotonicity
Injections
subcutaneous injection  not necessary
intramuscular injection  must be isotonic
intravenous injection  isotonic in large volume
intrathecal injection
(subarachnoid/subdural space)
 strict isotonicity
Eye drops  not necessary
Nasal drop  not necessary
Isotonicity reduces pain on injection or administration

8. Adjustment of isotonicity
• freezing point depression
• molar concentration
• sodium chloride equivalents

9. Freezing point depression
Freezing point of blood plasma and tears : － 0.52 ℃
Solution which freezes at － 0.52 ℃ have the same
osmotic 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

10. Molar concentration
0.28 mol/L solution is isotonic with blood plasma and
tears
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

11. Sodium chloride equivalents
The mass (gram) of NaCl that has an effect on freezing point
depression 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