JNTU Pharm. D II Year PHARMACOLOGY-I Previous Question Paper (October/November - 2019 - R08)

Routes of drug administration are broadly classified into enteral, parenteral, and topical routes.

• Enteral (Oral, Sublingual, Rectal): Oral administration is convenient, safe, and economical, but suffers from slow onset, first-pass metabolism, and potential gastric irritation. Sublingual administration provides rapid absorption and avoids first-pass metabolism, though it is limited to lipid-soluble drugs. Rectal administration is useful for unconscious patients or those with vomiting, but absorption can be irregular.
• Parenteral (Intravenous, Intramuscular, Subcutaneous): Intravenous administration offers immediate onset and 100% bioavailability, but carries risks of infection, embolism, and requires skilled administration. Intramuscular and subcutaneous routes allow for depot formulations and controlled release, though they may cause pain or tissue damage.
• Topical (Inhalation, Transdermal, Ocular): These provide localized effects with minimal systemic side effects. Inhalation allows rapid absorption via the large alveolar surface area, while transdermal patches offer sustained systemic delivery, though they are limited to highly lipophilic drugs.

Toxicity studies are categorized based on the duration of exposure to the substance:

• Acute Toxicity: Refers to the adverse effects occurring within a short period (usually 24 hours) following a single dose or multiple doses of a drug administered within that timeframe. It is primarily used to determine the median lethal dose (LD50).
• Sub-acute Toxicity: Involves repeated administration of a drug over a period of 1 to 3 months. This study helps identify cumulative toxic effects and target organ damage that may not appear in acute studies.
• Chronic Toxicity: Involves long-term administration of a drug, typically lasting 6 months to 2 years (or the lifespan of the animal model). It is essential for assessing the potential for carcinogenicity, reproductive toxicity, and long-term organ system failure.