From which of the following routes, bioavailability of the drug is likely to be 100 percent?

(b) Intravenous,Ref: Lippincott, 6th ed., pg. 3-4 and Sharma & Sharma's 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 (s/c) route. But bioavailability is not 100 %. In s/c 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., s/c and id), the drug may precipitate at the site of injection, leading to their lesser bioavailability as compared to iv route.