Overview And Classification Of Pharmaceutical Liniment

Liniments are solutions or mixtures that are dense liquid or gelatinous mass that melts at body temperature. They consist of various substances in oil, alcoholic solutions of soap, or emulsions and may contain suitable antimicrobial preservatives. These preparations that may be liquid or semi-liquid are intended for external application and should be labeled. They are rubbed onto the affected area; because of this, they were once called embrocation.

Liniment

They are applied with friction and rubbing of the skin, the oil or soap base providing for ease of application and massage. Dental liniments are solutions of active substances which are rubbed into the gums, but they are no longer official.

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Some liniments are solely used as protective coating depending on the ingredients in the preparation. Liniments should not be applied on bruises and broken skin. Liniments that are emulsions or that contain insoluble matter must be shaken thoroughly before use to ensure even distribution of the dispersed phase.

These are typically formulated from alcohol, acetone, or similar quickly evaporating solvents and contain counterirritant aromatic chemical compounds such as methyl salicylate, benzoin resin, menthol, or capsaicin. Some lubricants may contain soap which helps in the easy application of liniment on the skin. They produce a feeling of warmth within the muscle of the area they are applied to, typically acting as rubefacients via a counterirritant effect.

General Uses Of Liniments

Liniment contains medicament possessing analgesic action, rubefacient, counter-irritant properties and applied in joint pain, muscle pain, etc. Liniments are typically sold to relieve pain and stiffness, such as from sore muscular aches and strains, or arthritis.

1. Antipruritic - used to relieve itching

2. Astringents - causes biological tissue to contract

3. Emollients - products that soften skin or treat dry skin

4. Analgesics Rubefacient-Substance that causes redness

5. (Rubar) Counterirritant- an agent applied locally to produce superficial inflammation with the object of reducing inflammation in deeper adjacent structures

Method Of Preparing Liniment

Depending on their individual ingredients, liniments are prepared in the same manner as solutions, emulsions, or suspensions, as the case may warrant. The vehicle should be selected for the type of action desired (rubefacient, counterirritant, massage) and also on the solubility of the desired components in the various solvents prepared in the same manner as solutions, emulsions, or suspensions. Should be dispensed in the colored fluted bottle.

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1. Homogenous liniments are usually compounded directly in a dry vial for handling. Dense and viscous liquids (turpentine, tar, fatty oils) are dosed by weight, as well as liquids with high density (perhydrol, concentrated acids).

2. Soluble medicinal substances are included into liniments according to their solubility in the prescribed components. They are dissolved in the solvent in which they have the best solubility and then they are mixed with other ingredients.

3. While compounding liniments suspensions, the medicinal substances insoluble in the prescribed liquids are powdered in the mortar using the Deryagin's rule and then they are mixed with liquid components. As the dispersion environment is dense and viscous, surfactants (stabilizers) are not included into the composition of suspension liniments if they are not prescribed by the doctor. The suspension's stability is reached due to a high viscosity of the medium.

4. Emulsive liniments are prepared using emulsifiers according to the general rules for compounding emulsions. In some cases, emulsion liniments are prepared in a vial for dispensing, because emulsion is formed readily.

The volatile and odoriferous substances are added last.

General Classification Of Liniment

There are two types of Liniments. They are alcoholic liniments and oleaginous liniments.

Alcoholic Liniment

In alcoholic preparation, alcohol helps in the penetration of medicament to the skin and also increases its counter-irritant effect and rubefacient action. Alcoholic liniments are intended generally for their rubefacient, counterirritant, mildly astringent and penetrating effects. They penetrate the skin more readily than the oil base.

Oleaginous Liniment

In oily liniments, arachis oil is commonly used which spreads more easily on the skin. By their nature, oleaginous liniments are less irritating to the skin than alcoholic liniments. They are milder in their action but are more useful when massage is desired.

Classification Of Liniments By The Type of Dispersion Environment

1. Fatty liniment (liniment pinguia seu olimenta): fatty oils (sunflower and flax seed oils are often used) are included as a dispersion environment.

2. Alcohol liniment (capsicum tincture and others are included as a dispersion environment).

3. Vaseline liniment includes Vaseline oil. Due to its high chemical inertness, they are very stable when stored.

4. Siliments: silicon liquids are included as a dispersion environment.

5. Soapy-alcohol liniment: the alcoholic solutions of soaps are included as a dispersion environment. They can be liquid (if they contain potassium soap), dense or gel-like.

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Classification of Liniments by the Type of Disperse System

1. Liniments-solutions are transparent mixes of fatty oils with essential oils, chloroform, methyl salicylate, ester, turpentine. Prescribed medicinal matters are dissolved in the prescribed solvents.

2. Liniments-suspensions are the 2 phased systems (suspensions of powdered medicinal substances insoluble in prescribed liquids).

3. Liniments-emulsions are the 2 phased systems which can be emulsions of oil/ water or water/oil type.