Overview Of Pharmaceutical Solution

Solutions are homogeneous liquid dispersion of a solute (solid, liquid or gas) dissolved in a suitable vehicle (water, alcohol or any other solvent mixture). Components of solutes are in lower proportion compared to solvent. Pharmaceutical solutions are used for many routes of administration, including oral, rectal, vaginal, ophthalmic, parenteral, and otic.

Pharmaceutical solution

Solutions intended for oral administration usually contain sweeteners, flavors, and colors to make the medication more attractive and palatable to the patient. They may contain stabilizers to maintain the physicochemical stability of the drug and preservatives to prevent the growth of microorganisms in the solution.

Solution instill into eyes, ear or other body tissues must be isotonic to avoid irritation. Parenteral solutions or solutions for direct administration to mucosal tissues should be isotonic or hypotonic to avoid local tissue stress and pain upon administration.

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Tonicity is usually adjusted using dextrose or sodium chloride. Isotonic sodium chloride is a 0.9% w/v concentration of NaCl in water and is also called normal saline. A 5% w/w dextrose, also known as glucose, solution in water is also isotonic. These are commonly used infusion fluids for intravenous administration.

A drug dissolved in an aqueous solution is generally in the most bioavailable form. As the drug is already in solution, no dissolution step is necessary before systemic absorption occurs.

Many pharmaceutical chemicals are only slowly soluble in a solvent and require an extended time for complete dissolution. To increase the dissolution rate, several techniques such as applying heat, reducing the particle size of the solute, utilizing a solubilizing agent, or subjecting the ingredients to rigorous agitation can be employed. ensure the materials are heat stable and non-volatile when using heat to facilitate the dissolution of rice.

Formulation Of Solution

The following are added to some solution in addition to the drug;

A. Vehicle

Portable Water: water from tap that is not from any storage and safe for drinking

Freshly Boiled And Cool Water: water that may be contaminated must be boiled to 100°c and cooled to room temperature before use

Purified Water: gotten from some distillation techniques in the laboratory when the above is not available

Aromatic Water: they have flavouring, therapeutic and/or preservative properties

Medicaments: some vehicle come with some therapeutic effect e.g. Senegal infusion with expectorant properties

B. Adjuvant

Chemical stabilizer: prevent chemical degradation of the preparation

Preservatives: prevent microbial degradation. Not necessary for broad spectrum antibiotics

Colours and flavour: add aesthetic appeal to the product

Quality Attributes Of Solution

Important quality attributes of a solution dosage form include potency; physical, chemical, and biological stability; palatability; deliverability of the dose; and dosage uniformity.

Physical

Any physical changes that can be felt. These include colour, odour, precipitation, etc.

Chemical and Biological Stability

Lack of unacceptable degradation of the chemical components of the product throughout the storage period under recommended storage conditions. The active pharmaceutical ingredient (API) must be potent for the stated period. Possible degradation are hydrolysis and oxidation because liquids are more prone to that as they contain carbohydrates.

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Palatability

The product should be easy to mask both taste, odour and colour

Deliverability

Too thick a solution and the product may not flow out if it's a container. Solution must be deliverable and get to the site of action

Dosage Uniformity

Dosage uniformity is very important in pharmacy products. If you have ever tried to drink from a frozen bottle of soft drink, you will understand this better. The sugar melts first leaving other ingredients in the frozen parts. The initial fluid is extra sweet but the frozen parts will only be water. In pharmacy, it is called precipitation or crystallization of the sugar. This kind of mixture can lead to wrong dosage.

A good solution must have the API evenly distributed throughout the container and even between bottles. Viscosity of the formulation is an important determinant of its deliverability and uniformity of content.