Introduction To Dosage Form

INTRODUCTION TO DOSAGE FORMS

  • Drug substances are seldom administered in their isolated form; they are typically provided as dosage forms or drug delivery systems.

    • Example: Acetaminophen serves as the active pharmaceutical ingredient (API) in paracetamol tablets.
    • The tablet represents the dosage form, while acetaminophen is the drug.

  • Dosage Form Definition: A dosage form is a physical state of a pharmaceutical formulation that contains the active drug and other inactive ingredients necessary to create that specific physical form.

  • Common Dosage Forms: Solutions, tablets, capsules, semisolids, injections, and aerosols.

    • Proper design and formulation of a dosage form entail careful consideration of the physical, chemical, and biological characteristics of both the drug and the excipients used in the product.

  • Importance of Dosage Form:

    • Certain medical conditions necessitate specific routes of administration.
    • Oral administration may be unsuitable in cases of dysphagia, nausea, and vomiting.
    • Alternative routes include parenteral, topical, or inhalation.
    • For example, in joint pain, a local application via the topical route is preferred.

CHARACTERISTICS OF IDEAL DOSAGE FORM

  • Dosage forms must involve a combination of the active drug and non-drug substances, along with additional materials that may not be recoverable post-use.
  • An ideal dosage form must exhibit the following characteristics:
    • Easy and safe to administer
    • Easy to handle
    • Reproducibility and manufacturability
    • High patient compliance
    • Efficacious
    • Physically and chemically stable
    • Biocompatible
    • Economical for the patient
    • Maintains therapeutic activity throughout its shelf life

THE NEED FOR DOSAGE FORMS

  • Purpose: Drug substances rarely are consumed without additives due to challenges in precise dosing and achieving the desired therapeutic effect.

    • The combination of the drug and excipients transforms them into various suitable dosage forms such as solutions, tablets, capsules, suspensions, emulsions, ointments, and pastes.
    • Therapeutic Level: Dosage forms ensure the drug reaches the desired therapeutic level.

  • Challenges with Low Dose Potent Drugs:

    • Administering a drug in milligrams or micrograms can be problematic for patients (e.g., weighing 0.1 mg of Levothyroxine).
    • This results in patient inconvenience; therefore, correct dosage forms (e.g., tablets, capsules) are necessary to facilitate easier handling through the use of bulking agents (diluents).

  • Objectives of Dosage Form Design:

    • Enhance drug stability to prolong shelf life.
    • Ensure accurate dosing.
    • Deliver the drug in an appropriate format.

PRIMARY REASONS FOR DESIGNING A DOSAGE FORM

  1. Protection

    • Protects the drug from environmental factors such as atmospheric oxygen, temperature, and humidity (e.g., through coated tablets, capsules, or ampoules).
    • Prevents degradation of acid-labile drugs from gastric acid using enteric-coated formulations.

  2. Improvement of Therapeutic Activity

    • Provides optimal drug action from topical application sites (e.g., ointments, creams, transdermal patches).
    • Facilitates direct placement of drugs in bodily orifices (e.g., rectal or vaginal suppositories).
    • Ensures optimal drug action in bloodstream or body tissues (e.g., injections, inhalants, inhalation aerosols).
    • Supports rate-controlled drug action (e.g., prolonged release delivery).
    • Enhances bioavailability of drugs with narrow absorption windows via gastroretentive delivery methods.

  3. Patient Compliance

    • Ensures dosage accuracy through unit-dose delivery methods (e.g., tablets, capsules).
    • Reduces dosing frequency via sustained and prolonged release techniques.
    • Masks unpleasant tastes or odors of drugs using film-coated tablets, flavored syrups, or sugar-coated options.
    • Allows drug placement within body tissues and cavities (e.g., otic, rectal, vaginal, buccal, sublingual applications).
    • Offers ease of handling and administration, exemplified by chewable tablets.

CLASSIFICATION OF DOSAGE FORMS

  • Classified based on:
    • Physical Form
    • Route of Administration

A. Physical Form

  1. Solid Dosage Forms

    • Examples: conventional and modified-release tablets, powders, capsules, films, lozenges, chewing gum, pellets.

  2. Liquid Dosage Forms

    • Examples: solution, syrup, elixir, spirit, aromatic water, tincture, injections, mouthwashes, gargles, suspension, emulsion.

  3. Semisolid Dosage Forms

    • Used for application on the skin and mucous membranes (e.g., otic, nasal, vaginal, or rectal).
    • Examples: ointments, creams, gels, liniments, lotions, pastes.

  4. Gaseous Dosage Forms

    • Active ingredients combined with propellants that emit fine liquid and/or solid dispersions in a gaseous medium.
    • Examples: aerosol, inhaler, nebulizer.

B. Route of Administration

  1. Oral Administration

    • Forms: powder, tablet (including buccal, sublingual, or orally disintegrating, modified release), capsule (hard gelatin and soft gels), and liquid forms (monophasic and biphasic).

  2. Topical Administration

    • Forms: cream, gel, liniment/balm, lotion, ointment, eardrops (otic), eyedrops (ophthalmic), skin patch (transdermal), vaginal rings.

  3. Parenteral Administration

    • Methods include:
    • Intradermal (ID): Injection in the dermal region.
    • Intramuscular (IM): Injection into a muscle.
    • Intraosseous (IO): Injection into the marrow of a bone.
    • Intravenous (IV): Infusion or injection directly into a vein.
    • Subcutaneous (SC): Administration as a bolus into the subcutaneous layer.
    • Intrathecal (IT): Injection into the spinal column.

  4. Inhalational

    • Forms: administered through nasal and pulmonary routes (e.g., aerosol, inhaler, nebulizer).

  5. Instilled in Body Cavities

    • Forms: suppository, douche, pessary, etc., for rectal and vaginal administration.

ORAL DOSAGE FORMS

  1. Tablet:

    • Hard, compressed medications with round, oval, or square shapes.
    • Contains unit doses of one or more medications, made through molding or compression methods.
    • Excipients include:
      • Binders, glidants (flow aids), lubricants to ensure effective tableting.
      • Disintegrants that ensure tablet breakup in the digestive tract.
      • Sweeteners or flavors to mask bad-tasting active ingredients.
    • Types of tablets include:
      • Buccal and Sublingual Tablets: Administered under the tongue or between the gum and cheek.
      • Effervescent Tablet: Uncoated tablets with acids and carbonates that react with water, releasing carbon dioxide for rapid dispersion.
      • Chewable Tablet: Designed for children, chewed before swallowing (e.g., vitamin products).

  2. Capsule:

    • Medication encased in a gelatin container.
    • Advantage: Masks the unpleasant taste of contents.
    • Types of capsules:
      • Hard Gelatin Capsules: Used for dry powders.
      • Soft Gelatin Capsules: Used for oils and active ingredients suspended in oil.

  3. Lozenge:

    • Solid mixture of sugar and gum, providing slow release of medication for throat or mouth remedies.

  4. Dental Cones:

    • Tablets inserted into empty sockets after tooth extraction to prevent bacterial growth; may contain antibiotics or antiseptics.

  5. Powder:

    • Mixtures of dry, finely divided drugs intended for internal or external use; made by suspending powders in appropriate vehicles upon dispensing.

  6. Solution:

    • Clear liquid preparations of active ingredients dissolved in a suitable vehicle for oral use.

  7. Emulsion:

    • Stabilized oil-in-water dispersions where oil is finely divided in water or vice versa.

  8. Suspension:

    • Liquid preparations containing suspended active ingredients; should be shaken before use to create a uniform mixture.

  9. Syrup:

    • Concentrated aqueous solution of sugar, usually sucrose, with medicaments added; typically flavored to mask disagreeable tastes.

  10. Elixir:

    • Clear liquid oral preparation of potent or nauseous drugs; contains high proportions of ethanol or sucrose for stability.

  11. Linctuses:

    • Viscous liquid preparations for cough relief, containing syrup and glycerol which provide soothing effects.

  12. Gargles:

    • Aqueous solutions used for treating throat infections, instructed to dilute before use.

  13. Mouthwashes:

    • Similar to gargles, used for oral hygiene and treating infections in the mouth.

TOPICAL DOSAGE FORMS

  • Ointments:

    • Semi-solid, greasy preparations for application on skin, rectum, or nasal mucosa.
    • Bases are usually anhydrous, not miscible with skin secretions; used to apply suspended or dissolved medicaments.

  • Creams:

    • Semi-solid emulsions (mixtures of oil and water), classified as:
    • Oil-in-Water (O/W) Creams: Comfortable and cosmetically acceptable, less greasy, easily washed off.
    • Water-in-Oil (W/O) Creams: Difficult to handle, suitable for hydrophobic drugs.

  • Gels (Jellies):

    • Semisolid systems that contain liquid phases constrained within a polymeric matrix used for medication and lubrication.

  • Liniments:

    • Fluid, semi-fluid or semi-solid preparations, intended for skin application, often massaged in; should not be applied to broken skin.

  • Lotions:

    • Fluid, aqueous preparations for application without friction or covered to reduce evaporation.

RECTAL DOSAGE FORMS

  1. Suppository:

    • Small, solid medicated mass designed for rectal or vaginal insertion, melting at body temperature.

  2. Enema:

    • Procedure for introducing liquid into the rectum and colon via the anus.

VAGINAL DOSAGE FORMS

  • Pessary:
    • Solid medicated preparations inserted into the vagina, melting or dissolving upon insertion.

PARENTERAL DOSAGE FORMS

  • Parenteral forms include large volume injections referred to as infusions or injections, prepared under sterile conditions. Types of injections:
    • Intravenous (IV): Administered directly into the bloodstream via veins for rapid effects.
    • Intramuscular (IM): Injection into a muscle, commonly used for vaccinations.
    • Subcutaneous (SC): Injection into the subcutaneous layer, effective for vaccines and insulin.

INHALED DOSAGE FORMS

  • Inhaler:

    • Solutions, suspensions, or emulsions of drugs released through pressure in an aerosol dispenser, allowing patient inhalation.
    • Example: Ventolin Inhaler.

  • Nebulizer (Atomizer):

    • Device converting liquid medicine into a mist for inhalation; commonly used in respiratory treatments.
    • Generally preferred over inhalers in severe cases of respiratory disease.

OPHTHALMIC DOSAGE FORMS

  1. Eye Drops:

    • Saline drops used for medication administration in the eye, may include steroids, antihistamines, or lubricants.

  2. Ophthalmic Ointment & Gel:

    • Sterile semi-solid preparations for conjunctiva or eyelid margin application.

OTIC DOSAGE FORMS

  • Ear Drops:
    • Solutions, suspensions, or emulsions intended for instillation into the ear to treat or prevent infections, particularly in the outer ear and ear canal.

NASAL DOSAGE FORMS

  • Nasal Drops and Sprays:
    • Drugs in solution instilled into the nose for local effect, such as antihistamines or decongestants.