Liquid dosage forms commonly encountered in pharmaceutical practice are either monophasic or biphasic. Monophasic Liquid Preparation Method is used in preparation Solutions.

A solution is a homogeneous one-phase system consisting of two or more components. It contains two-phases i.e., solvent and solute. The solvent is the phase in which the dispersion occur and solute is that component which is dispersed as small ions or molecules in the solvent. In general, solvent part is greater than solute in the solution except a few preparation, e.g., Syrup BP, it contains 66.7% w/w of sucrose as solute and 33.3% of water as the solvent.

Advantages of Solutions

1. Easy to swallow than solid dosage form like tablet and capsules.

ADVERTISEMENTS:

2. Drug in solution form is immediately available for absorption.

3. A solution is a homogeneous system and therefore the drug remains uniformly distributed throughout the preparation.

4. Suitable for drugs that can irritate and damage the gastric mucosa, if localized in specific area. The irritation is reduced by administration in solution form.

Disadvantages of Solutions

ADVERTISEMENTS:

1. Inconvenient to transport and store because they are bulky.

2. Whole product is lost immediately if any breakage in the container.

3. The stability of most of substances in aqueous solution is less than solid dosage form.

4. Shelf life of solution is shorter than solid preparation.

ADVERTISEMENTS:

5. Suitable media for the microbial contamination and may therefore require suitable preservatives.

6. Dose inaccuracy compared to solid dosage form.

7. Bitter unpleasant substances are not suitable for solutions and need sweetening and flavoring agent to make them more palatable.

Formulation of Solution

ADVERTISEMENTS:

Following additives are generally required for the preparation of solution.

1. Solvents: a. aqueous b. Non-aqueous (fixed oil, alcohol, polyhydric alcohol, dimethy1- sulphoxide, ethyl ether, liquid paraffin, etc.

2. Buffers: Carbonates, citrates, gluconates, lactates, phosphate, tartrate, borates, etc

3. Colors: water soluble dye amaranth.

ADVERTISEMENTS:

4. Density modifiers

5. Flavors and perfumes

6. Taste

(a) Salty: Apricot, butterscotch, liquorice, peach, vanilla

ADVERTISEMENTS:

(b) Bitter: Anise, chocolate, mint, wild cherry

(c) Sweet: Vanilla fruits

(d) Sour: Citrus fruits, raspberry

7. Preservatives

8. Antioxidants and reducing agents

Container

Narrow mouth, screw capped colorless plain bottle.

Example:

Prepare and dispense Aqueous Iodine Solution (Lugol’s solution)

Iodine 5.0 g

Potassium iodide 10.0 g

Purified water 100.0 ml

Method of Dispensing:

Dissolve potassium iodide and iodine in purified water and mix thoroughly.

Example:

Prepare and dispense Strong Iodine Solution

Iodine 10.0 g

Potassium iodide 6.0 g

Purified water 10.0 ml

Ethanol, sufficient to produce 100.0 ml

Method of Dispensing:

Dissolve potassium iodide and iodine in purified water and add sufficient ethanol to produce 100 ml.

Example 04:

Prepare and dispense Weak Iodine Solution

Iodine 2.0 g

Potassium iodide 2.5 g

Purified water 10.0 ml

Ethanol, sufficient to produce 100.0 ml

Method of Dispensing:

Dissolve potassium iodide and iodine in purified water. Add sufficient ethanol to produce 100 ml.