Liquid Dosage Forms in Pharmacy

Liquid Dosage Forms

• Presented by Dr. Mohamed Ali Attia Shafie, Professor of Pharmaceutics.
• Liquid dosage forms are preparations made by dissolving the active ingredient(s) in an aqueous or non-aqueous solvent.

Pharmaceutical Solutions

• Classified as aqueous or sweet/viscid non-aqueous.
• Aqueous solutions include: douches, enemas, gargles, mouthwashes, nasal washes, juices, sprays, otic solutions, inhalations.
• Sweet/viscid non-aqueous solutions include: syrups, honeys, mucilages, jellies, elixirs, spirits, collodions, glycerins, liniments, oleo vitamin.

Advantages of Solutions

• Easier to swallow, useful for children, elderly, and unconscious patients.
• More quickly effective than tablets and capsules.
• Homogenous, provides uniform dose without shaking (unlike suspensions or emulsions).
• Dilute irritant action and minimize adverse effects. Examples include aspirin, KI, and KCl.

Disadvantages of Solutions

• Bulky, difficult to transport and store.
• Unpleasant tastes or odors are difficult to mask.
• Requires accurate measuring tools (e.g., spoons).
• Less stable than solid dosage forms. Instability can be indicated by color changes, precipitation, microbial growth, or chemical gas formation.

Additives

• Buffers: Used to resist pH changes.
• Isotonicity Modifiers: Used to maintain appropriate osmotic pressure for injections and applications to mucous membranes; dextrose and NaCl are commonly used.
• Viscosity Enhancement: Used to improve the topical solutions' ability to stay on the skin or in the eye (often necessary for low concentrations of thickening or gelling agents).

Preservatives

• Solutions can become contaminated due to raw materials, equipment, environment, or patient use.

• Preservatives should be effective against a wide spectrum of microorganisms, stable over their shelf life, nontoxic, non-sensitizing, and compatible with other ingredients, free of taste and odor.

• Examples include: alcohols, acids, esters and quaternary ammonium compounds.

  • Alcohols: Ethanol (needs high concentration to be effective); propylene glycol is also useful.
  • Acids: Benzoic acid and sorbic acid have low water solubility, effective at low concentrations (0.1% to 0.5% or 0.2 %) with low pH.
  • Esters (parabens): Methyl, ethyl, propyl, and butyl parabens from p-hydroxybenzoic acid; they are effective over a wide pH range (4-8)
  • Quaternary ammonium compounds: Benzalkonium chloride (at low concentrations 0.002 to 0.02%). Its use is optimal over 4-10 pH range and stable in most temperatures; incompatible with anionic compounds.

Antioxidants

• Vitamins, essential oils, and fats/oils can oxidize. Heat, light, and heavy metals can initiate oxidation.
• Solutions should be stored in cool, light-resistant containers for oxidisable drugs.
• Heavy metal effects minimized by citric acid and ethylenediamine tetraacetic acid (EDTA).
  • Antioxidants include propyl & octyl esters of gallic acid, tocopherols or vitamin E, sodium sulfite and ascorbic acid.

Sweetening Agents

• Sucrose is the most common.
• Polyhydric alcohols (sorbitol, mannitol and glycerol) have sweetening power and are used in diabetic preparations.

Flavors and Perfumes

• Used to mask unpleasant tastes or odors, and for easy identification of the products.
• Natural flavors (fruit juices, peppermint oil, lemon oil) are generally cheaper but can be less stable than artificial flavors.

Stability of Solutions

• Physical and chemical stability of solutions are important for maintaining their desired properties (clarity, color, odor, taste, and viscosity) throughout their shelf life.

Classification of Solutions

• Classified according to the vehicle (aqueous or non-aqueous).

Aqueous Solutions

• Homogenous mixture of a solid, liquid, or gas dissolved in water (the vehicle).
• The vehicle of aqueous solutions can include water, aromatic water, extracts.

Water

• Used as a vehicle and a solvent for flavoring or medicinal ingredients.
• Water is typically tasteless, odorless, lacking pharmacological activity, and inexpensive.

Types of Water

• Tap water: Not commonly used due to potential bacterial contamination and dissolved salts that can affect active ingredients.
• Freshly boiled and cooled water: Boiling might kill some vegetative bacteria but not necessarily spores; and storage can lead to microbial regrowth.
• Purified water: Prepared by distillation, deionization, or reverse osmosis and used for most pharmaceutical operations.
• Water for injection: Specifically for parenteral solutions, requiring sterilization of pyrogen-free distilled water.

Aromatic Waters

• Clear, saturated aqueous solutions of volatile oils or substances.
• Typically flavored, perfumed vehicles.
• Volatile oils can cause an incompatibility problem (salting out) when high concentration of salt is added.
• Should be stored in small quantities in air-tight, light-resistant containers to minimize deterioration.

Methods of Preparation of Aromatic Waters

• Distillation: The drug is mixed with purified water, distilled, and the excess oil is filtered out.
• Solution: The volatile substance is shaken with purified water, allowed to sit, and then filtered. Talc can be used to increase the surface area and filtration.

Methods of Preparation of Solutions

• Simple solution: Dissolving the solute in a suitable solvent. Solvents may include other ingredients to stabilize or solubilize the solute.
• Solution by Chemical Reaction: Reacting two or more solutes in a solvent to create a new solution (e.g., Calcium carbonate plus lactic acid).
• Solution by Extraction: Plant or animal materials are extracted to form a solution.

Infusion

• A dilute solution of readily soluble components of crude drugs.
• Prepared by macerating the drug in either cold or warm water.
• Earthenware vessels are often used for preparations.
• Freshly prepared, or preserved, occasionally in concentrated form.

Decoction

• Similar to infusions, but more potent due to the extraction of components from tougher herbal parts (like roots, barks, seeds, or dry fruits).

Maceration Process

• A method for preparing liquid extracts, typically for substances that are less readily soluble.
• Involves placing the material in a closed container with the solvent, allowing it to stand for several days, then straining and perhaps expressing the liquid.

Explore the key concepts of liquid dosage forms in pharmacy, presented by Dr. Mohamed Ali Attia Shafie. Learn about the classification, advantages, and disadvantages of various pharmaceutical solutions. This quiz covers both aqueous and non-aqueous preparations and their applications.