Discussion

The solubilities are: benzocaine 1 in 2500 in water and 1 in 8 in alcohol; lidocaine base is insoluble in water and very soluble in alcohol; lidocaine HCl is very soluble in water and 1 in 1.5 in alcohol; tetracaine HCl is 1 in 7.5 in water and 1 in 40 in alcohol. The quantity of benzocaine is large, which means that a suspension must be prepared as indicated by the composition. The purpose and benefit of adding a small amount of DMSO are unclear. For lidocaine, the water-soluble form lidocaine HCl is used, and tetracaine HCl will also dissolve in water.

Preparation Method

1. Tare a sufficiently large mortar (M1) with pestle and spatula and record the tare weight.
2. Reduce the benzocaine to a fine powder in a separate mortar.
3. In M1, mix the Klucel with DMSO and glycerol.
4. Gradually add the pulverized benzocaine to the mixture in M1 while mixing thoroughly.
5. Then add lidocaine HCl and tetracaine HCl to this mixture.
6. Measure 25 g of aqua conservans and add it gradually to mortar M1 while stirring well. The water-soluble medicinal products dissolve and the Klucel gradually swells.
7. Then gradually add another 50 ml of aqua conservans while stirring well and mix until homogeneous.
8. Place the mortar with pestle and spatula on the balance and top up with water to 100 g.
9. Mix the suspension until homogeneous.

Post-treatment of the suspension with a rotor-stator homogenizer improves the quality.