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30/10/2025, 00:02 Pharmaceutical Solutions & Sterile Dosage Forms
3. Viscosity enhancers
These are usually hydrocolloids (hydrophilic polymers). They are used to prepare highly viscous
solutions, suspensions and gels.
Examples of viscosity enhancers used in solutions:
Non-ionic (neutral) polymers: cellulose derivatives (methylcellulose MC, hydroxyethyl
cellulose, hydroxypropyl cellulose) and polyvinyl- pyrrolidone (PVP)
Ionic polymers: sodium carboxymethylcellulose (anionic) and sodium alginate (anionic).
N.B. Certain liquid formulations may not require the addition of viscosity enhancers such as
syrups due to their inherent viscosity.
The viscosity of the formulation must be sufficiently controlled to ensure the accurate
measurement of the volume to be dispensed.
They can also be classified based on their nature into:
Natural: Gums as acacia, tragacanth & agar
Semi-synthetic: PVP, MC, CMC
Synthetic: Carbopols
4. Preservatives
Most aqueous solutions will support microbial growth unless this is prevented by the addition of
antimicrobial preservatives.
Anti-microbial preservatives are used to preserve multidose preparations.
Examples of preservatives used in oral solutions:
Benzoic acid and salts, sorbic acid and its salts and alkyl esters of para-hydroxybenzoic acid
(parabens).
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