Liquid Oral Preparation: Advantages, Disadvantages, Classification, definitions: Solutions, Aromatic Water, Syrup, Elixir, Spirit, Tincture, Solutions for injections. Solution for External Applications: Ophthalmic Solution (Eye Drops), Otic Solutions (Ear Drops), Nose Drops, Mouth Washes, Gargles, Topical Solutions.

Liquid oral preparation: Solution, Syrup, Elixir, Emulsion, Suspension, Dry Powder for Reconstitution

Liquid dosage forms are pharmaceutical preparations in liquid state for internal or external applications. Some examples of liquid dosage forms are solution, syrup, elixir, emulsion, suspension, dry powder for reconstitution, etc.

Advantages:

• 1. Easy to Swallow: Easy to swallow than solid dosage form. Most suitable for pediatric and geriatric patients

• 2. Rapid absorption: Rapid rate of absorption than solid dosage form.

• 3. Rapid action: Rapid onset of action than a solid dosage form

• 4. Dose uniformity: Homogeneous dosage form thus uniform distribution of medicaments in liquid dosage form

• 5. Good acceptability: More acceptability among pediatric and child patients due to its good appearance, flavor, and taste.

• 6. Easy to measure: Easy to measure by using household measures,

• 7. Easy to adjust dose: Easy to adjust dose as per individual patient requirement

• 8. Mild to GIT: Some drugs produce GIT irritation in solid dosage form. They can be administered in liquid dosage form.

• 9. Suitability: Some drugs can be administered only in liquid dosage form.

Disadvantages:

Liquid dosage forms are bulky, heavy, and reactive during storage. These all cause the following disadvantages:

• 1. Difficult to transport.

• 2. Difficult to store.

• 3. Difficult to dispense.

• 4. Difficult to mask unpleasant taste and odor.

• 5. Difficult to preserve.

• 6. Low stability thus shorter duration of self life.

• 7. Low dose accuracy due to the use of household measures.

Classification

• 1. Monophasic liquid dosage form

  • i. Monophasic liquid dosage form for internal application: Solutions, Syrup, Aromatic water, Elixir, Drops, Linctuses, etc

  • ii. Monophasic liquid dosage form for external application: Lotion, liniments, eye drops, ear drops, nose drops, gargles, mouthwash, inhalation, etc.

• 2. Biphasic liquid dosage form

  • i. Emulsion

  • ii. Suspension

SOLUTION

The solution is a clear, homogeneous liquid dosage form containing solutes in a solvent. Ingredient in large amount in solution acts as a solvent to dissolve solutes such as solid, liquid, or gas. The solvent is in a liquid state. Solutions may be for internal applications or external applications.

• 1. Solutions for internal applications: Examples are aromatic water, syrup, elixir, spirit, tincture, and solutions for injections.

• 2. Solution for external applications: Ophthalmic solution (Eye drops), otic solutions (ear drops), nose drops, mouthwashes, gargles, Topical solutions. etc.

Aromatic water: Aromatic water is a saturated solution of essential oil or similar substances. It is prepared by the dissolution of essential oil or similar substances in purified water or by steam distillation of plants containing essential oils. Examples are rose water, dill water, camphor water, chloroform water, etc. Aromatic water is used as a vehicle in several medicinal preparations It enhances the flavor and fragrance of dosage form. It makes dosage form more appealing and palatable. Some aromatic water also acts as a preservative and carminative.

Elixir: It is a clear pleasantly flavored, sweetened hydroalcoholic solution for oral administration. There are two types of elixir. These are flavored elixirs and medicated elixirs. Ethanol and water are the main ingredients of elixir. Elixir also contains glycerine, sorbitol, propylene glycol, sugar, flavoring agent, sweetening agent, and preservative. Flavored elixir is mainly used as a vehicle example aromatic elixir USP. Medicated elixir contains potent drugs such as antihistaminics, sedatives, etc. Example piperazine citrate elixir, paracetamol elixir, ephedrine elixir, etc.

Drops: Drops include eye drops, ear drops, and nasal drops.

Eye drops (Ophthalmic drops): Eyes drops are sterile isotonic liquid dosage form meant to be instilled in-between eyelids and eyeballs. Normally it contains medicament with antiseptics, anti-inflammatory, mydiatric, or miotic effects. Medicines to treat eye dryness, glaucoma, eye infection, inflammation, allergies, etc are dispensed as eye drops. It is dispensed in a glass or plastic container with a screw cap containing a rubber teat and dropper. Examples artificial tears, pilocarpine eye drops, atropine eye drops, etc.

Ear drops: Ear drops are liquid preparations meant to be instilled into the ear by using a suitable dropper. Medicines are dissolved or suspended in water, dilute alcohol, glycerine, or propylene glycol. Ear drops contain medicaments to treat ear infections, inflammation, and ear pain or to remove the buildup of earwax.

Nasal drops: Nasal drop is an aqueous solution meant to be instilled into the nasal cavity. They contain medicaments to produce antiseptic, local analgesic, or vasoconstrictor effects.

Syrups: It is a thick sweet aqueous solution of sugar or similar substances with or without medicaments and flavoring agents. Syrup containing medicaments is called medicated syrup. Syrup containing no medicaments is called non-medicated syrup.

Simple syrup IP is a thick sweet concentrated solution containing 66.7% w/w sugar in water. Syrup containing less than 65% w/w sugar in water supports the growth of molds and bacteria. Syrup containing 66.7% w/w or more sugar in water does not support the growth of molds and bacteria. Saturated solution of sugar in water is prone to crystallization on variation of temperature. Thus syrup should be prepared in small quantities to be used immediately. Preparation of large quantities needs to be preserved by adding preservatives like methyl paraben, propyl paraben, benzoic acid, or sodium benzoate. It should be stored at room temperature.

Emulsion:

The emulsion is a mixture of two immiscible liquids in which one liquid is dispersed as globules in another liquid. It is a biphasic liquid dosage form in which the dispersed phase (internal phase) is distributed as globules in the continuous phase (external phase). An emulsifying agent is used to disperse the internal phase into the external phase (continuous phase). There are two types of emulsion:

• 1. Oil in water type emulsion (O/W type emulsion)

• 2. Water in oil-type emulsion (W/O type emulsion)

• Oil in water emulsion (O/W emulsion): Dispersion of oil globules in water by using an emulsifying agent forms oil in water emulsion. Oil is the dispersed phase and water is the dispersion medium. Emulsion for internal use is preferred as O/W emulsion. Dispersion medium water masks the unpleasant taste and odor of oil in the dispersed phase. Oil is in the dispersed phase as fine globules that have a large surface area. It helps rapid absorption of oil from GIT into the blood.

• Water in oil emulsion (W/O emulsion): Dispersion of water globules in oil by using an emulsifying agent forms water in oil emulsion. Water is the dispersed phase and oil is the dispersion medium. Water in oil emulsion is preferred as an emulsion for external application.

• W/O emulsion and O/W emulsion are referred to as macro emulsion. Macroscopically they behave like a true solution and appear as homogeneous preparations. However, macroemulsions are pseudo-solution and heterogeneous preparations.

Alok Bains