Drug Forms and Classifications

Drug Forms

• Drugs are classified into various forms based on their physical characteristics.
• Solid form includes tablets, capsules, suppositories, and pessaries.
  • Tablets are compressed medications in different shapes.
  • Capsules enclose medications in gelatin containers. Hard-shelled capsules typically contain dry powders; soft-shelled capsules hold liquids or substances dissolved in oil.
  • Suppositories are for rectal use, often containing cacao butter.
  • Pessaries are for vaginal use, often containing gelatin or theobromine oil.
• Semisolid form comprises ointments and oculentum.
  • Ointments are semisolid preparations usually containing Vaseline.
  • Oculentum (eye ointment) uses lanolin.
• Liquid form includes solutions, syrups, decoctions, infusions, emulsions, liniments, collyrium, enemas, and tinctures.
  • Solutions dissolve active ingredients in a suitable vehicle for oral use.
  • Syrups are concentrated sugar solutions, often sucrose.
  • Decoctions are prepared by boiling dried plant material in water for 10 minutes.
  • Infusions involve soaking dried plant material in water.
  • Emulsions mix immiscible liquids, often using acacia as an emulsifying agent.
  • Liniments are liquids or viscous preparations for external use, with anodyne properties (e.g., camphor).
  • Collyrium (eye lotion) is a weak watery solution used as an antiseptic.
  • Enemas are rectal administrations for constipation treatment.
  • Tinctures dissolve non-volatile substances in alcohol (e.g., iodine).
• Gaseous form consists of gases and aerosols.
  • Gases, such as oxygen, are used medicinally.
  • Aerosols contain tiny liquid or solid drug particles dispersed in a gas, often delivered via spray or inhalation.

Routes of Drug Administration

• Drug administration can be categorized in several ways including location of absorption.
• Body orifices (oral, nasal, respiratory, rectal, vaginal, and urethral).
• Parenteral (intravenous, intramuscular, subcutaneous, intraperitoneal, intra-cardiac, intra-articular, and epidural).
• Topical (local).
• Factors influencing the choice of route include
  • Drug form
  • Physical and chemical properties of the drug
  • Required rapidity of response
  • Nature and location of the disease.

Oral Route Details

• Oral administration, or Per Os (by mouth), is convenient and affordable.
• Ideal oral drugs are:
  • Palatable
  • Non-irritating
  • Stable in the intestinal and gastric pH
  • Unaffected by digestive juices
  • Adequately absorbed

Advantages and Disadvantages of Oral Administration

• Advantages: Convenient, Economical, Available in various forms, Generally safe
• Disadvantages: Difficult handling, Cannot be used for unconscious patients or in emergencies, Unsuitable for GIT disturbances, Some drugs are inactivated by gastric acidity or enzymes, Some drugs are irritants.

Nasal Route Details

• Nasal administration is used for localized effects like treating rhinitis and for vasoconstrictive action.
• Drugs are in the form of drops, sprays, or inhaled gases.

Rectal Route Details

• Rectal administration (Per Rectum) uses suppositories or enemas.
• Local effects include purgative, evacuation of the intestine, and treatment of colitis.
• Systemic effects include antibiotics, but absorption is slower than oral absorption.

Urethral Route Details

• Urethral administration involves catheter insertion and is used for localized effects on the urethra, prostate, and bladder.

Parenteral Routes Details

• Parenteral routes inject drugs directly into the body tissues.
• Advantages: Rapid action, Useful for drugs not absorbed orally, Useful for unconscious patients or in emergencies, useful when GIT disturbance is present.
• Disadvantages: Inconvenient to administer, Difficult to administer safely to ensure the intended effect, potential for adverse injection sites, risk of infection if not sterile technique used.

Intravenous (IV) Injection

• Rapid onset and short duration of action.
• Used for emergency situations, administration of large doses, and diluting substances irritating to other tissues.

Intramuscular (IM) Injection

• Slower absorption than IV, longer duration of action.
• Used for moderate irritants.

Subcutaneous (SC) Injection

• Slower absorption than IM.
• Used for non-irritant drugs avoiding local damage.

Intraperitoneal (IP) Injection

• Very rapid absorption.
• Used if IV and other absorption routes are not possible; appropriate for lab animals.

Intra-Cardiac injection

• Used in emergency cases requiring rapid action, such as cardiac arrest.

Intra-articular Injection

• Injecting drugs directly into synovial fluid (joint capsule), often for joint inflammation conditions.

Epidural Injection

• Injecting drugs into the epidural space around the spinal cord.
• Used for regional anesthesia.

Topical Administration

• Placing drugs on the skin or mucous membranes for localized effects.
• Examples: Counterirritants, anti-inflammatory, antiseptics.
• Systemic absorption is rare.
• Absorption is slower through skin than other body membranes.