Solutions, Mixtures & Elixirs: Monophasic liquid dosage forms

MONOPHASIC LIQUID DOSAGE FORMS

Mono-Single

Monophasic – single phase dosage forms

Examples: solutions, aromatic waters and tinctures

A.  SOLUTIONS

Monophasic system of two or more substances, e.g. sodium chloride solution,

Pharmaceutical solutions are defined as the liquid preparations containing one or more chemical substances usually dissolved in water.

Methods of preparation

1. Simple dissolution:

Solute + suitable solvent → with/without heat → solution

e.g. Morphine hydrochloride solution, Adrenaline hydrochloride solution.

2. Solution by chemical reaction:

Reaction of two or more solutes → in suitable solvent.

e.g. Aluminium acetate solution

Al₂(SO₄)₃+3CaCO₃ +4CH₃COOH → 2Al.(CH₃COO)₂.OH +3CaSO₄ +3CO₂ +H₂O

 3. Solutions by extraction:

Removal of active constituents from crude drugs with the help of solvent.

e.g. liquid extracts and tinctures.

Solutions for internal use:

Taken orally: mixtures, elixirs, tinctures, draughts and syrups.

Used in mouth and throat: mouth washes, gargles, throat paints and throat sprays.

Instilled into body cavities: douches, enemas, ear drops, nasal drops and nasal sprays.

Advantages of solutions taken orally:

Absorption rate is high.

Uniform dose is possible.

Easy to swallow.

Doses can be adjusted as per need of patients.

Attractive appearance.

Safe for administration of salts that cause gastric irritations, KI and KBr.

They are homogeneous, medicament/drug is uniformly distributed.

Disadvantages of solutions taken orally:

Bulky – difficulty in transportation.

Less stable than solid dosage forms.

Breakage of container causes complete loss and contamination of medicament.

Sometimes unpleasant taste cannot be masked.

 

B. MIXTURES

Mixtures are liquid oral preparations in which the drug is dissolved, dispersed or suspended in vehicle.

a) Vehicles

1. Water: distilled water

2. Aromatic water: these are primarily used for flavors but some have therapeutic properties. Also act as preservative agents. These are prepared from concentrated preparations (dilution of concentrated preparations). .eg. Anise water, Chloroform water, Dill water, cinnamon water, Caraway water,etc.

b) Additives:

1. Antioxidants: these prevent oxidation. .eg. ascorbic acid, sodium bisulphite, sodium metabisulfite, BHT,BHA.

2. Colours: e.g. Sunset yellow, Erythrosin, Amaranth,Tartrazine.

3. Flavours: e.g aromatic waters, lemon syrup, orange syrup, liq. Extract of liquorice, etc.

4. Antimicrobial agents: to prevent microbial contamination in the preparations. E.g. Benzoic acid, chloroform, phenyl mercuric nitrate.

Examples of mixtures:

Strong Iodine solution IP: Potassium iodide + iodine +alcohol+ water.

Cresol soap solution (antiseptic): Cresol +vegetable oil+ potassium hydroxide + water.

Morphine hydrochloride solution (analgesic): Morphine hydrochloride+ water + hydrochloric acid+alcohol.

C. ELIXIRS

Elixirs are liquid hydro-alcoholic preparations intended for oral administration. Potent and nauseous drugs are prepared palatable by formulating as elixirs. Elixirs are more stable than mixtures.

Examples of drugs: antibiotics, sedatives and antihistamines.

Bitter taste and nauseous odor is reduced by addition of flavors.

Advantages:

More stable than mixtures.

Nauseous and bitter drugs can be formulated as palatable preparations.

These are less sweet and less viscous than syrup.

CLASSIFICATION OF ELIXIRS:

1. Non-medicated elixirs: (these do not contain medicament and are used as flavoring vehicles)

e.g. Aromatic elixir, compound benzaldehyde elixir.

2. Medicated elixir: (these contain medicaments)

e.g Piperazine citrate elixir.

Chloral hydrate elixir,

Diphen hydramine elixir,

Chlorpheniramine maleate elixir.

METHOD OF PREPARATION OF ELIXIRS

These are prepared by simple dissolution of medicaments in respective solvents (alcohol and water) with agitation and finally mixing water part with alcohole part.

Alcohol soluble ingredients are dissolved in alcohol part while water soluble ingredients are dissolved in water part.

Remember: always aqueous solution (water part) is added into alcoholic solution in order to avoid separation of alcohol soluble ingredients.

FORMULATION OF ELIXIR

1. Vehicle: water, alcohol, glycerine, sorbitol, propylene glycol.

2. Additives:

a) Coloring agents: amaranth, sunset yellow, Tartrazine.

b) Sweetening agents: sorbitol, invert syrup, Saccharine, glycerol.

c) Flavouring agents: orange spirit, lemon spirit, liq. Extract of liquorice.

d) Preservatives: Preservatives are used only when the concentration of alcohol is below 20 %. E.g chloroform water.

(above 20% alcohol content- alcohol in the preparation itself acts as a preservative)

Examples:

Ephedrine compound elixirs (ephedrine sulphate, caffeine, sodium salicylate, sodium iodide, alcohol)

Phenobarbital elixir (phenobarbital, alcohol, glycerine, syrup, orange oil)

Vitamin B complex elixir.

Chloral hydrate elixir (chloral hydrate, syrup water, black currant syrup)

How to store elixirs?

Since elixirs contain alcohol and volatile oil which decompose in presence of light and air. They should be stored in tightly closed container away from light or should be stored in tightly closed amber colored containers in cool place.