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30/10/2025, 00:02 Pharmaceutical Solutions & Sterile Dosage Forms

Although usually aqueous, they may also contain cosolvent(s) such as glycols (polyethylene

glycol (PEG) or propylene glycol), alcohols (ethanol), or other non-aqueous solvents (glycerine)

These solutions are usually filtered through 0.22 µm membrane to achieve sterility.

Solutions that don't contain any antimicrobial agents should be terminally sterilized.

Autoclaving is the preferred method for terminal sterilization whenever drug solutions can
withstand heat.

Any microbial agent is often added to SVPs that cannot be terminally sterilized.

2.2. Suspensions

For insoluble drugs in water.

Given via IM or SC: Prolonged (depot) effect. This will ↓ drug dissolution rate in tissue fluids and
result in ↓ absorption rate and sustained effect.

Common particle size range 5-10 µm.

Parenteral suspensions should be easily resuspended and passed through an 18-to-21-gauge
needle through their shelf-lives.

To achieve these properties, it is necessary to select and carefully maintain particle size
distribution, zeta potential, rheological properties and wettability.

Injectable suspensions often consist of the active ingredient (insoluble) suspended in an
aqueous vehicle containing a microbial preservative, a surfactant, a suspending agent, a buffer
and/or salt.

Due to the inherent long term physical instability of suspensions, parenteral suspension
dosage form are formulated as dry powder for reconstitution immediately before use in a
sterile vehicle.

Example: penicillin G procaine injectable suspension USP, testosterone injectable suspension
USP.

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