BSO - Parenteral

Parenteral Dosage Forms

Parenteral medicines are administered by injection, bypassing the body’s primary protective barriers: the skin and mucous membranes. The term parenteral comes from Greek roots meaning “beside the intestine.”

Requirements for Parenteral Products

Parenteral products should:

• Be sterile and free of pyrogens or endotoxin contamination.
• Be free of visible particulate matter when formulated as injectable solutions.
• Be isotonic or close to isotonicity. Isotonicity is especially important for intravenous administration.
• Remain chemically, physically, and microbiologically stable throughout their shelf life.
• Be compatible with their solvents, medical devices, and any medicines given at the same time.

Main Parenteral Dosage Forms

• Solutions: The drug is completely dissolved, producing a homogeneous, clear preparation without particles. The vehicle is sterile water or another water-based liquid.
• Suspensions: Used for drugs that are unstable in liquid solutions or poorly soluble. They are heterogeneous, and their solid particles may settle over time, so they should be shaken before use. Suspensions can prolong drug action and may be given intramuscularly, subcutaneously, or intra-articularly. They must not be given intravenously because particles could obstruct blood vessels.
• Emulsions: Dispersions of two or more liquids that normally do not mix. They often look cloudy or white because their interfaces scatter light. Their absorption and drug permeation can be controlled. Particle size is important: large droplets may cause emboli and are clinically unacceptable, while smaller droplets support physical stability and prolonged circulation.
• Implants: Designed to release medicine continuously over a long period, reducing the need for repeated injections and potentially improving patient compliance. They may be inserted through minor surgery or delivered using a large-bore needle or trocar. Implants may be biodegradable or non-biodegradable; non-biodegradable implants must eventually be removed. Development considerations include biocompatibility, biostability, low toxicity, tissue-compatible structure, environmental stability, and removability when needed. Polymers and polymeric membranes can control drug release.
• Dry powders for injection: Used when a drug is unstable in liquid form. They are reconstituted before use, and preparation and calculations must be accurate to ensure the correct dose.

Reconstitution and Displacement Value

A solid drug powder occupies volume when dissolved, displacing some of the added solvent. The displacement value is the volume of solvent displaced by a specified quantity of solid. It is used to calculate the final solution volume and concentration.

Example:

1. A vial contains 1 g of ceftriaxone powder.
2. Its stated displacement value is 0.72 mL.
3. Add 3.5 mL of solvent.
4. The final volume is 0.72 + 3.5 = 4.22 mL.
5. The resulting concentration is 1,000 mg ÷ 4.22 mL ≈ 236 mg/mL.

Speakers and Source

• Narrator: An unnamed narrator delivers the educational voice-over.
• Publishing source: Department of Pharmacology & Therapy, FM-PHN UGM.