Cpding Equip, Supplies & Techniques

Compounding Equipment & Supplies

Learning Objectives

  • Upon completion of this section, students should be able to:

    • Recognize common supplies and equipment used for compounding and explain their function.

    • Differentiate between balances used in compounding and understand their purpose.

    • Understand different compounding techniques and when to use them.

Common Equipment & Supplies

  • Weighing Papers: Used for weighing powders and other substances.

  • Weighing Boats: Similar function to weighing papers but preferred for larger amounts or messy substances.

  • Spatulas: Instrument for mixing or transferring materials.

  • Ointment Pads or Ointment Slabs: Surfaces used to prepare ointments.

  • Graduates:

    • Must use the smallest graduate that will measure the target amount.

    • It is advisable to use one graduate rather than two for measuring quantities.

    • Important to read the measurement at the bottom of the meniscus.

Other Equipment & Supplies

  • Pipettes:

    • Never fill by mouth suction.

  • Oral Syringes:

    • Use without a needle for liquid delivery.

  • Droppers:

    • Never allow the solution to enter the bulb to avoid contamination.

  • Rubber or Synthetic Gloves: For hand protection.

  • Hand Protection for Hot Equipment:

    • Use padded graspers or oven mitts.

  • Stirring Rods: For mixing solutions.

  • Funnels:

    • Must be used with filter paper for proper filtration.

Key Equipment

Mortar & Pestle

  • Mortar: The bowl used to hold substances.

  • Pestle: The rod with a rounded end used for grinding or mixing.

    • Used extensively for:

    • Crushing tablets to prepare oral suspensions.

    • Trituration: Grinding a powder to produce a very fine powder.

    • Mixing powders: Example of diluting morphine with lactose using geometric dilution.

    • Emulsifying: Mixing a liquid containing water, oils, and emulsifying agents.

Equipment - Balances

  • Ingredients are weighed on three different types of balances:

    • Torsion Balance:

    • Manual balance.

    • Weighs amounts from 0.05 ext{ g} to 60 ext{ g}.

    • Bulk or Beam Balance:

    • Suitable for amounts greater than 60 ext{ g}.

    • Electronic Balance:

    • Capable of measuring quantities as small as 0.001 ext{ g}.

    • Maximum quantities vary.

    • Must be tared with the paper or weighing boat in place.

    • Has a single pan for weighing; does not require adding weights like other balances.

Key Balances and Their Types

Torsion Balance

  • Manual balance handling weights between 0.05 ext{ g} and 60 ext{ g}.

Bulk or Beam Balances

  • Includes types such as the Triple Beam Balance and Harvard Trip Balance.

  • Suitable for weighing larger quantities over 60 ext{ g}.

Electronic Balance

  • Capable of measuring small quantities (as low as 0.001 ext{ g}) with high precision.

Additional Equipment

  • Evaporating Dish: Used for evaporating solvents from a solution.

  • Water Bath: Provides controlled gentle heating for melting solids.

  • Hot Plate: Used to provide heat for various laboratory processes.

    • Example in use: Melting PEG 400 and 8000 for use as a suppository base through a fusion method.

Compounding Techniques

  • Trituration: The act of grinding a chemical to a fine powder.

  • Levigation:

    • Rubbing the drug powder with roughly an equal amount of a liquid in which it is not soluble.

    • Moistening the powder ('wetting').

  • Geometric Dilution: Mixing together two unequal quantities to ensure uniformity.

  • Fusion: Melting substances together using heat.

  • Dissolution: The process of dissolving a substance.

  • Eutectic Mixture:

    • Example substances: Camphor and menthol are two crystalline substances that, when combined, will melt into a liquid state; this is observable with other combinations like phenol with either menthol or camphor.

    • Important note: Do not touch chemicals with bare fingers (e.g., phenol crystals can be corrosive).

  • Mechanical Incorporation:

    • Use of spatulas for mixing, known as spatulation.

Examples of Techniques

Levigation

  • Involves adding a small amount of liquid to the powdered drug to create a paste.

  • The drug remains insoluble in the levigant liquid, while the levigant liquid is soluble in the ointment base.

  • Example leviagants:

    • Mineral oil for water-in-oil (w/o) ointment bases.

    • Glycerin for oil-in-water (o/w) cream bases.

Dissolution

  • Using a solvent to dissolve the drug before incorporation into the ointment base.

  • The drug must be soluble in the solvent used; also, the solvent must be miscible in the ointment base.

  • Examples include:

    • Urea crystals dissolved in hot water.

    • Menthol crystals dissolved in alcohol.

Eutectic Mixture

  • A phenomenon where two substances, when combined, will melt into a liquid.

  • Important combinations include camphor with menthol or phenol with camphor and menthol.

  • Always exercise care and avoid direct contact with corrosive substances like phenol crystals.