Pharmaceutical Quality Control: Sterile and Solid Dosage Forms

The LAL test is 5 to 50 times more sensitive than the rabbit test. However, practitioners must be aware that certain drugs, such as vancomycin, oxacillin, meperidine, or promethazine, can interfere with the test results.

Sterility Testing

Per USP <71>, every sterilized batch must undergo sterility testing to confirm the absence of viable microorganisms. This is typically performed using culture media such as Trypticase Soy Broth (TSB) or Fluid Thioglycollate Medium (FTM), with the samples being incubated for 14 days. There are two primary methods:

• Direct Inoculation: The product or medical device remains in direct contact with the test media throughout the entire 14-day incubation period.
• Membrane Filtration: The sample effluent is passed through a cellulose nitrate or cellulose acetate membrane filter designed to retain microorganisms. The filter is then transferred to specific nutrient test media and incubated for 14 days.

Sterilization Quality Control

To validate that a sterilization process is functioning correctly, manufacturers use biological indicators. These indicators consist of highly resistant endospores (bacterial spores), which are among the toughest microorganisms to kill. By using these specific markers, manufacturers can gain confidence that the sterilization conditions were sufficient to eliminate more vulnerable microbes.

The choice of biological indicator depends on the sterilization method used:

Tablet Manufacturing and Quality Control

While sterile products focus on biological purity, solid oral dosage forms like tablets focus on physical and chemical consistency. The shape of a tablet is determined by the punch contours used during compression, which can include flat faces, shallow cups, standard cups, deep cups, or modified balls.

Physical Parameters

Quality control for tablets involves several critical physical tests:

• Weight and Thickness: The USP Weight Variation Test requires testing 20 tablets from a lot. No more than two tablets may deviate from the mean percentage. For example, a $130\text{ mg}$ tablet has a $10%$ allowable deviation, while tablets $> 324\text{ mg}$ have a $5%$ limit. Thickness is measured via micrometer and should ideally maintain a $\pm 5\%$ variation to ensure efficient packaging.
• Hardness (Crushing Strength): This measures the force required to break a tablet diametrically. Typical ranges include $4\text{--}10\text{ kg}$ for oral tablets, $3\text{ kg}$ for chewable tablets, and $10\text{--}20\text{ kg}$ for sustained-release formulations.
• Friability: This test measures the tablet's durability against mechanical stress. The percentage weight loss ($B$) is calculated as:

$$\begin{aligned} B &= \frac{100[W_0 - W]}{W_0} \end{aligned}$$

where $W_0$ is the initial weight and $W$ is the final weight. A loss of $\le 1\%$ is generally considered acceptable.

Chemical and Performance Parameters

• Content Uniformity: This is essential for low-dose, high-potency drugs to ensure the amount of drug per tablet matches the label value (e.g., within an $85\%\text{--}115\%$ range).
• Disintegration: This measures the time required for a tablet to break down into smaller particles. Standard times include $< 3\text{ min}$ for sublingual tablets, $\approx 30\text{ min}$ for uncoated tablets, and up to $2\text{ hours}$ for coated tablets.
• Dissolution: This measures the rate and extent to which a solute enters a solution. Testing typically utilizes Paddle or Basket apparatus to ensure the drug release profile matches the intended bioavailability.

Exam Tip: Remember that while disintegration tells you if the tablet breaks into pieces, dissolution tells you if the drug actually enters the solution to be absorbed. A tablet can disintegrate without necessarily dissolving its active ingredient efficiently.

Pharmaceutical Packaging and Labeling

Packaging must be selected based on the dosage form to ensure stability and protection. For example, solutions ready for injection may be packaged in glass vials, while dry products might be in blister packs.

Labeling is a critical safety component. Labels must clearly communicate:

• The name of the preparation
• The amount of active ingredient and the amount of solvent to add (for reconstitutable products)
• The route of administration
• Storage conditions and expiration date
• Manufacturer/distributor information and the lot number