<prompt> From which of the following routes, bioavailability of the drug is likely to be 100 percent?SubcutaneousIntravenousIntramuscularIntradermal  <response>: b Intravenous,Ref: Lippincott, 6th ed., pg. 3-4 and Sharma Sharmas Principles of Pharmacology, 3rd ed., pg. 18-20This is very simple question. When we give a drug by Intravenous iv route, the drug enters the systemic circulation directly, bypassing the 1st pass metabolism, so there is 100 bioavailability by this route. Absorption is also predictable by Intramuscular i.m. route, it is less variable as compared to oral and subcutaneous sc route. But bioavailability is not 100 . In sc route, absorption is smooth but slower as compared to iv and i.m. route. Again, bioavailability is not 100 . By intradermal id route, absorption is very slow and only a small volume of drug can be injected. In routes other than iv i.m., sc and id, the drug may precipitate at the site of injection, leading to their lesser bioavailability as compared to iv route. 