Routes of Administration in Pharmacology

Routes of Administration

• Enteral: Oral (tablets, capsules, controlled/sustained release), sublingual, buccal, nasogastric tube, rectal.
  • Pros: Convenient, inexpensive, self-administered.
  • Cons: Subject to first-pass effect, potential gastric irritation, slow onset, requires consciousness, risk of vomiting.
• Parenteral: Intravenous, intramuscular, subcutaneous, intradermal, epidural.
  • Pros: Rapid effect, avoids gastric irritation, suitable for unconscious patients.
  • Cons: Requires aseptic technique, can be painful, expensive, risk of nerve injury, requires training.
  • Depot injection: Delivers medication for prolonged release.
• Topical: Transdermal, ocular (eye), otic (ear), vaginal.
  • Pros: High local concentration, minimal systemic effect.
  • Cons: Slow effect, localized action, limited drug options, possible systemic effect with tissue damage.
  • Transdermal patch administration: Clean a dry area, wash hands, remove patch, apply firmly for 10-30 seconds, dispose of old patch, rotate application sites, wash hands again, and follow manufacturer instructions.
• Inhalation: Vaporization, gas inhalation, nebulization.
  • Pros: Rapid effect, large surface area for absorption.
  • Cons: Difficult to control dosage.
• Factors affecting route choice: Drug properties, desired site of action, rate/extent of absorption, digestive juice effects, first-pass metabolism, response onset, dose accuracy, and patient condition.

Pharmacokinetics

• Absorption: Drug entry into the bloodstream.
  • Factors affecting absorption: Route of administration, drug solubility, pH levels, presence of food.
  • Bioavailability: Fraction of drug reaching systemic circulation.
• Distribution: Transport of drug from blood to target tissues.
  • Factors affecting distribution: Blood flow to tissues, lipid solubility, plasma protein binding, blood-brain barrier, fetal-placental barrier.
• Metabolism: Chemical modification of drugs, primarily in the liver.
  • Factors affecting metabolism: Age, liver function, drug interactions.
• Excretion/Elimination: Removal of drugs and metabolites, mostly through urine.
  • Factors affecting excretion: Kidney function, urine pH, age.
• First-Pass Metabolism: Initial liver metabolism before reaching systemic circulation.
  • Primarily affects oral formulations.

Pharmacodynamics

• Agonist: Drug that binds to a receptor to induce an effect.
• Partial Agonist: Drug that induces a partial effect at the receptor.
• Antagonist: Drug that binds to a receptor but doesn't induce an effect.
• Loading dose: High initial dose to quickly achieve therapeutic levels.
• Maintenance dose: Lower dose to maintain therapeutic levels.
• Peak level: Highest drug concentration in the blood.
• Trough level: Lowest drug concentration in the blood.
• Onset of action: Time to reach minimum therapeutic effect.
• Peak effect/level: Time to reach maximum therapeutic effect.
• Duration of action: Time drug concentration remains within therapeutic range.
• Therapeutic Index/Window: Dosage range with therapeutic effect without toxicity.
  • High/wide index is safer than low/narrow index.
• Half-life: Time for plasma drug concentration to decrease by half.
• Efficacy: Maximum therapeutic response a drug can produce.
• Potency: Amount of drug needed to produce a specific effect.
• Tolerance: Increasing drug doses needed to elicit same effect.
• Dependence: Body reliance on a substance, causing withdrawal symptoms.

Drug Effects

• Side effects: Predictable, expected effects at therapeutic doses.
• Adverse effects: Harmful, undesirable effects occurring at or above therapeutic doses.
• Black Box Warning: FDA warning of severe adverse effects.
• Allergic reactions: Immune response, rapid onset.
  • Mild: Pruritus, rash.
  • Anaphylaxis: Severe, involves multiple systems, treat with epinephrine.
• Toxicities:
  • Teratogenicity: Fetal harm, birth defects.
  • Nephrotoxicity: Kidney damage (monitor BUN, creatinine).
  • Hepatotoxicity: Liver damage (monitor liver function tests).
  • Neurotoxicity: Brain/nerve damage (headache, neuropathy, confusion).
  • Dermatologic toxicity: Skin damage (rash, pruritus, Stevens-Johnson Syndrome).
  • Ototoxicity: Ear damage (tinnitus, hearing loss).
  • Musculoskeletal toxicity: Muscle/tendon damage (rhabdomyolysis, tendonitis).
  • Bone marrow suppression: Impaired RBC, WBC, and platelet production (anemia, fatigue, infection, bleeding).
  • Cardiotoxicity: Heart damage (prolonged QT interval, Torsade's).

Drug Interactions

• Interactions can alter drug action.
• Examples: Warfarin and green leafy vegetables, statins and grapefruit juice, acetaminophen and alcohol, MAOI antidepressants and certain foods.
• Stevens-Johnson Syndrome (SJS): Severe skin reaction triggered by medications, infections, or other factors.

Explore the various routes of drug administration, including enteral, parenteral, and topical methods. Understand the pros and cons of each route and how they impact drug delivery and patient care. This quiz is essential for students in pharmacology and healthcare fields.