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, economical, and safe, but has slow onset and potential for first-pass metabolism. Sublingual provides rapid absorption bypassing first-pass metabolism, though it is limited to lipid-soluble drugs. Rectal is useful in vomiting or unconscious patients but can be erratic and irritating.
• Parenteral (Intravenous, Intramuscular, Subcutaneous): Intravenous provides rapid, precise control of drug levels but carries risks of infection and immediate adverse reactions. Intramuscular allows for depot preparations and moderate absorption, though it may be painful. Subcutaneous is suitable for self-administration (e.g., insulin) but absorption is slow.
• Topical (Inhalation, Transdermal, Ocular/Nasal): Inhalation offers rapid absorption via the large surface area of the lungs, ideal for respiratory drugs. Transdermal provides sustained, controlled release, though it is limited to highly lipophilic drugs.

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

• Acute Toxicity: Refers to the adverse effects occurring within a short period (usually 24 hours) following a single dose or multiple doses administered within that timeframe. It is 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 toxicity and target organ damage during intermediate-term exposure.
• Chronic Toxicity: Involves long-term administration of a drug, typically lasting 6 months to 2 years (or the lifespan of the animal). This is essential to evaluate potential carcinogenic, mutagenic, or long-term organ-specific toxic effects that do not manifest in shorter studies.