Liquid dosage forms are designed for easy absorption. The body quickly carries the active ingredients through the system and triggers the required response. But the greatest advantage of this medicinal type is its flexibility in formulation and dispensation. From lotions and syrups to drops and sprays, liquid solutions can be adapted to different administration routes including parenteral, topical, and oral. The fundamental liquid dosage manufacturing process involves dissolving or suspending solutes in a fluid. But that is not enough. A precise blend of excipients is needed to make the medicine go down.
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Use water or pure alcohol as a solution in the liquid dosage manufacturing process
The liquid dosage form is prepared by dissolving the active ingredient within a liquid vehicle to form a solution. Depending on the type of liquid vehicle used, you obtain either aqueous or non-aqueous solutions.
The aqueous solutions have water as the solvent, while the non-aqueous solutions have hydro-alcoholic (water and alcohol as solvents) and alcohol (only alcohol as solvent). Elixirs and tinctures are examples of hydro-alcoholic solutions. The concentration of alcohol in elixirs is 3%-25%, while the concentration of alcohol in tinctures is 25%-60%.
Apply size reduction to raw materials to facilitate solubility
Drops, syrups, elixirs, and draughts are monophasic liquid dosage forms, retaining the components in a single liquid phase. The APIs in most dosage forms of this type are weak acids or weak bases with low solubility properties. The formulation, therefore, requires adjustment of pH levels.
One method to improve solubility is by reducing the particle size of pharmaceutical powders. Using a mill or a spray drying system, grind the materials to 10 microns or less.
Apply gravimetric measurement in the liquid dosage manufacturing process
The volumetric measurement risks a high variability in liquids as the ingredients may be subjected to volume contraction or expansion.
The gravimetric method bypasses the effects of temperature and ambient forces acting on the ingredients. By measuring the density of the total contents, the technique gives a more reliable reading of the liquid dosage before filling and packing.
Control the hydrophilic-lipophilic balance when processing emulsions
Emulsions are formulations with two liquids that do not mix. These two main types of emulsion manufacturing are water in oil (W/O) emulsions and oil in water (O/W) emulsions.
Measuring the hydrophilic-lipophilic balance (HLB) presents a principal challenge in this liquid dosage manufacturing process. Emulsifiers with HLB values greater than 10 are more hydrophilic and thus better at stabilizing o/w emulsions. In contrast, emulsifiers with HLB values less than 10 are more hydrophobic and better suited for w/o emulsions.