dosage form

Introduction to Dosage Forms

  • Definition: Dosage forms, also known as Drug Delivery Systems, refer to the forms in which drugs are administered to the body.

  • Variability: A single drug can be available in various dosage forms to cater to the preferences of physicians and patients, address specific drug characteristics, ensure product stability, and enhance patient convenience.

Need for Suitable Dosage Forms

  1. Protection from Environmental Factors: Safeguards drugs from atmospheric oxygen and moisture (e.g., coated sealed capsules or tablets).

  2. Gastric Protection: Shields drugs from gastric juices after oral administration (e.g., enteric-coated tablets).

  3. Taste Masking: Conceals bitter taste or unpleasant odor (e.g., capsules, coated tablets, flavored syrups).

  4. Stability in Preparation: Converts insoluble or unstable drugs into liquid preparations (e.g., suspensions).

  5. Extended Drug Action: Achieves delayed drug release (e.g., retarded-release tablets, spansules).

  6. Topical Application: Provides optimum drug action when applied topically (e.g., creams, ointments, drops for ears, eyes, or nose).

  7. Insertion Administration: Supplies drugs via rectal or vaginal routes (e.g., suppositories).

  8. Injection Delivery: Supplies drugs directly into body tissues (e.g., injections).

  9. Inhalation Administration: Delivers drugs through inhalation for respiratory effects.

Components of a Dosage Form

  1. Drug Component: The active pharmaceutical ingredient.

  2. Non-drug Components: Also known as adjuvants, excipients, or auxiliary materials, these components modify the dosage form’s action, altering the amount, duration, or intensity of the drug's effect.

Characteristics of a Dosage Form

  1. Stability in Various Conditions: Must not deteriorate in temperature and humidity.

  2. Microbial and Chemical Stability: Must be stable against microbial contamination, oxidation, or degradation.

  3. Acceptability for Patients: Should have appropriate shape, taste, color, flavor, and usability.

Routes of Administration

Overview

  • The route of administration is the path through which a drug (dosage form) comes in contact with the body.

  1. Enteral Route: Involves administering drugs via the gastrointestinal tract.

  2. Topical Route: Administration onto the skin or mucous membrane.

  3. Parenteral Route: Administration directly into the bloodstream or tissues.

  4. Inhalation Route: Administration through the respiratory tract.

Drug Effects

Categories

  • Systemic Effect: Affects the entire body; drugs are absorbed into the bloodstream and distributed throughout.

  • Local Effect: Limited to localized lesions; minimal systemic absorption occurs, allowing for higher concentrations at the target site without affecting the rest of the body.

The First-Pass Effect

  • Definition: Refers to the hepatic metabolism of a drug when absorbed from the gut and delivered to the liver via the portal circulation.

  • Implication: A greater first-pass effect means lower drug availability in systemic circulation when administered orally.

1. Oral Route

  • Involves administration via the mouth, either by topical application or swallowing for GI absorption.

  • Abbreviation: "PO" indicates oral administration.

Advantages

  • Most common, convenient for self-administration, effective for most drugs.

Disadvantages

  • Not suitable for:

    • Drugs rapidly inactivated by gastric/intestines or liver.

    • Patients undergoing surgery, those unconscious, vomiting, with absorption issues, or needing rapid therapeutic effects.

2. Buccal Route

  • Drug is taken into the mouth but not swallowed.

  • High blood flow through buccal mucosa facilitates systemic absorption, avoiding hepatic portal circulation in some cases.

3. Inhalation Route

  • Leverages high blood flow through lungs and large alveolar membrane surface for rapid systemic absorption.

  • Examples include: anesthetic gases, volatile liquids, and aerosolized drugs.

4. Rectal Route

  • Drugs administered into the rectum, absorbed mainly into systemic circulation with possible hepatic portal absorption.

  • Less predictable absorption than intestinal (oral) administration.

  • Uses: Systemic drugs that might irritate the GI, and for unconscious or vomiting patients.

5. Parenteral Route

  • Direct administration into circulation (e.g., intravenous).

  • Advantage: Rapid action by bypassing biological membranes that delay absorption.

6. Transdermal Route

  • Drug is applied to the skin and absorbed into systemic circulation slowly, offering sustained drug concentration.

  • Beneficial for drugs rapidly metabolized via the first-pass effect.

Specific Application of Oral and Topical Routes

Oral Route

  • Some dosage forms cater to local GI effects, such as antacids or topical applications for mouth ulcers.

Topical Route

  • Application to body surface epithelium for local effects (e.g., ointments or creams for skin, eyes, nostrils, rectum, vagina, or urethra).

Dissolution

  • Definition: The transition of a solid phase (e.g., tablet or powder) into a solution phase (e.g., water).

Drug Release

  • Definition: The process by which a drug separates from a drug product.

Types

  • Immediate Release: Fast dissolution of drug without intention to delay or extend absorption.

  • Modified-Release Dosage Forms: Changes in rate and/or place of active substance(s) release compared to conventional-release forms of the same route.

Modified-Release Dosage Forms

  1. Delayed-Release: Defined as drug release occurring at a time other than immediately following administration (e.g., enteric-coated).

  2. Extended-Release: These forms release active substance over a prolonged period compared to conventional-release forms.

Solid Oral Dosage Forms

Types

  1. Powder, Tablets, and Capsules

Advantages of Solid Dosage Forms

  1. Accurate dosage.

  2. Easy shipping, handling, and identification.

  3. Less shelf space required compared to liquids.

  4. No preservation requirements.

  5. No taste-masking issues.

  6. Generally more stable, allowing for longer expiration dates.

Categories Based on Manufacturing

  • Solid, Semi-solid, Liquid, and Sterile dosage forms.

1. Solid Dosage Forms

Capsules

  • Encompass medicinal or inert substances within a gelatin shell (hard or soft).

  • Generally intended for swallowing whole; some intended for sprinkling.

Gelatin Source

  • Obtained from hydrolyzed collagen from animal tissues.

  • Two types: Type A (acid) and Type B (alkali).

Storage

  • Store in airtight containers, protected from humidity (12%-16% water content is ideal).

Size

  • Hard capsules vary from size "000" (largest) to "5" (smallest).

2. Soft Gelatin Capsules

  • Oblong/spherical, contain glycerin or polyhydric alcohol as plasticizers for elasticity.

Usage

  • Often filled with oily liquids or dry powders.

Types of Drug Release

  • Immediate Release, Modified Release (Delayed & Extended Release).

3. Tablets

  • Unit doses of active medicaments prepared through compression, granulation methods.

Advantages

  • Simple and cost-effective preparation, stability, easy shipping, accurate dosing, high portability.

Coated Tablets Advantages

  1. Taste masking, improved appearance, protection from deterioration, reduced gastric irritation.

Types Based on Composition/Effects

  1. Oral Tablets: Conventional or enteric-coated.

  2. Sublingual Tablets: Bypass portal circulation for rapid absorption.

  3. Effervescent Tablets: Require dissolution in water before use.

  4. Buccal Tablets: Slowly release drugs avoiding the first-pass effect.

  5. Chewable Tablets: Designed to be chewed for rapid action; suitable for children and elderly.

4. Molded Solid Dosage Forms

Suppositories

  • Intended for rectal, vaginal, or urethral application for local or systemic effects.

Bases Used

  • Typically cocoa butter or glycerinated gelatin.

5. Liquid Oral Dosage Forms

Definition

  • Solutions prepared by dissolving substances in solvent (mostly water).

Types

  1. Aqueous Solution: Clear solutions for medications.

  2. Syrup: Concentrated aqueous solution of sugar, providing sweetness and viscosity.

  3. Elixirs: Hydro-alcoholic solutions, less sweet than syrups.

  4. Glycerites: Glycerin-based viscous liquids for medications.

Suspensions and Emulsions

Suspensions

  • Defined as well-formulated mixtures where particles do not settle promptly and are easily redisperse.

Advantages

  • Suitable for those unable to swallow solids, mask unpleasant tastes, manageable volume of active ingredients.

Emulsions

  • A two-phase system combining immiscible liquids to improve stability and bioavailability.

Types

  1. O/W (Oil in Water) and W/O (Water in Oil).

Advantages

  • Mask taste, improve drug stability, enhance topical formulation appearance.

Semi-Solid Dosage Forms

Creams

  • Soft forms for topical application, classified by water content (O/W or W/O).

Ointments

  • Semi-solid preparations often based on petroleum products for external application.

Gels

  • Semi-solid systems with a three-dimensional polymer matrix in a liquid.

Sterile Dosage Forms and Parenteral Preparations

Definition of Sterile

  • Free from all microorganisms.

Liquid Solutions for Injections

  • Prepared to be sterile and pyrogen-free using various suitable solvents.

Uses and Indications

  1. Rapid onset for emergencies.

  2. Depot drugs not absorbed via GI tract.

  3. Patients unable to swallow.

  4. To maintain stability of sensitive compounds.

Injection Routes

  1. Intravenous (IV)

  2. Subcutaneous (SC)

  3. Intradermal (ID)

  4. Intramuscular (IM)

  5. Intra-articular (IA)

  6. Intrathecal (IT)

Ophthalmic Preparations

  • Sterile dosage forms for application to the eyes for varied therapeutic functions, including eye drops, ointments, gels, and inserts.