Rx

Phenylephrine Hydrochloride (E=0.32) 1% Chlorobutanol (E=0.24) 0.5% Sodium Chloride q.s. Purified Water ad 15 mL make isoton. Sol. Sig. Use as directed.

 

______ milliliters of an 0.9% solution of sodium chloride should be used in compounding the prescription? Round to the nearest hundredth. Do not include units.

Comminution is the mechanical process of reducing the particle size of a solid substance to increase its surface area and improve dissolution rates. In compounding, various techniques are utilized to achieve a homogenous mixture or a fine viscous paste. These methods ensure that active pharmaceutical ingredients are uniformly distributed within a vehicle, which is essential for ensuring accurate dosage uniformity and therapeutic efficacy in topical or oral preparations.

Rationale:

A. Spatulation involves the blending of powders on a tile or paper using a spatula. This method is primarily used for mixing small quantities of powders or substances that may form eutectic mixtures when compressed. It does not utilize a mortar and pestle or a liquid agent for particle size reduction, making it incorrect for this specific grinding process.

B. Trituration is a method of comminution performed by grinding a dry substance in a mortar with a pestle. While it reduces particle size through continuous rubbing, it is typically a dry process. It lacks the specific requirement of adding a small amount of liquid to facilitate the grinding into a paste, which distinguishes it from the technique described in the question.

C. Levigation involves the reduction of particle size by grinding a powder with a mortar and pestle while incorporating a small amount of levigating agent, such as mineral oil or glycerin. This liquid helps "wet" the powder, facilitating the grinding process and creating a smooth, concentrated viscous paste. This is the classic method used to prepare fine particles for incorporation into ointments or suspensions.

D. Pulverization by intervention is a technique used for hard, crystalline solids that do not crush easily. It involves dissolving the substance in a "volatile" solvent, such as alcohol or acetone, which then evaporates as the powder is ground. This differs from the current scenario because the liquid used is temporary and intended for dissolution rather than creating a permanent paste or suspension.

E. Geometric dilution is a technique used to ensure the homogenous distribution of a potent active ingredient within a large amount of diluent. It involves adding the diluent in portions equal to the volume of the material already in the mortar. While it uses a mortar and pestle, it is a mixing strategy rather than a primary method of liquid-facilitated particle size reduction.

Step 1 is to calculate the Least Weighable Quantity (LWQ)

LWQ = (Sensitivity Requirement ÷ Acceptable Error) × 100

(5 ÷ 5) × 100

5 ÷ 5 = 1

1 × 100 = 100

Result at this step = 100 mg

Step 2 is to determine the drug multiplication factor

Since the required dose is 5 mg and we must weigh at least 100 mg:

Factor = 100 ÷ 5

100 ÷ 5 = 20

Result at this step = 20

Step 3 is to calculate the total mixture weight (drug + diluent)

Total Mixture = Aliquot weight × Factor

100 × 20 = 2000

Result at this step = 2000 mg

Step 4 is to calculate the amount of diluent needed

Diluent = Total Mixture - Drug weight

2000 - 100 = 1900

Result at this step = 1900 mg