BP102T • Unit 2Topic 2 of 3⏱ 5 Min Read
2. Routes of Drug Administration: Comparative Biopharmaceutics
💡 Core Concept & Clinical Context:
The route of administration is the path by which a drug formulation is brought into contact with the body. The selection of an administration route depends on the physicochemical properties of the drug (solubility, molecular weight, ionization), therapeutic urgency (routine vs emergency), site of intended action (local vs systemic), and patient physiological status (conscious, vomiting, pediatric).
Clinical Scenarios & Pharmacopoeial Examples:
1Comparison of Bioavailability and Onset across Routes
Differences in pharmacokinetic profile between Intravenous, Oral, Sublingual, and Transdermal routes.
Step-by-Step Breakdown:
•• Intravenous (IV): Onset = Seconds | Bioavailability (F) = 100% | Emergency drug delivery (e.g. Dopamine, Morphine).
•• Oral (PO): Onset = 30-60 min | Bioavailability (F) < 100% (Subject to gastric degradation & first-pass metabolism).
•• Sublingual (SL): Onset = 1-3 min | Bypasses liver first-pass metabolism (e.g. Isosorbide dinitrate).
•• Transdermal (TDD): Onset = Hours | Sustained steady-state release over multiple days (e.g. Fentanyl patch, Nicotine patch).
Comparison & Reference Table:
| Route | Onset of Action | Bioavailability ($F$) | Advantages | Disadvantages |
|---|---|---|---|---|
| Oral | 30 - 60 minutes | Variable (5% - 90%) | Safest, convenient, self-administered, non-invasive | Slow onset, destroyed by gastric acid, first-pass effect |
| Intravenous (IV) | Immediate (seconds) | Strictly 100% | Immediate effect in emergencies, precise blood levels | Invasive, pain, risk of embolism, irreversible if overdosed |
| Sublingual | 1 - 3 minutes | High (bypasses liver) | Rapid absorption, avoids first-pass metabolism | Limited to small-dose, lipid-soluble non-irritant drugs |
| Transdermal | Slow (hours to days) | Moderate to High | Continuous steady blood levels, improved compliance | Only for potent lipophilic drugs, risk of skin irritation |
📋Key Takeaways & Exam Highlights
- Enteral Routes: Oral, Sublingual, Buccal, Rectal (involves gastrointestinal tract).
- Parenteral Routes: Intravenous (IV), Intramuscular (IM), Subcutaneous (SC), Intradermal (ID) (bypasses GI tract).
- First-Pass Hepatic Metabolism: Pre-systemic clearance of orally absorbed drugs by hepatic enzymes before reaching systemic circulation.
- Bioavailability ($F$): 100% for IV injections; variable for oral dosage forms.
🇮🇳 हिन्दी व्याख्या (2. Routes of Drug Administration: Comparative Biopharmaceutics)
दवा देने के मुख्य रास्ते हैं: ओरल (मुंह से - सबसे सुरक्षित), IV (नसों में - 100% असर और तुरंत राहत), सबलिंगुअल (जीभ के नीचे - लीवर से बचे बिना तुरंत असर) और ट्रांसडर्मल (त्वचा पर पैच)।