A drug may be given by one of several routes, each of which has different characteristics.
Oral (PO) route:
(1) absorption variable and affected by many factors such as food and gastrointestinal disorders
(2) inability to swallow and vomiting restrict
(3) convenient and inexpensive
(4) usually the safest route
(5) requires patient cooperation and compliance
(6) absorption of drugs that are poorly soluble, unstable or slowly absorbed may be erratic and/or incomplete
Subcutaneous (SC) route:
(1) absorption of aqueous solutions prompt; absorption from repository preparations slow and sustained
(2) useful for implantation of solid pellets
(3) can be used for some insoluble suspensions
(4) not suitable for large volumes
(5) irritating substances can cause pain or necrosis of soft tissue
Intramuscular (IM) route:
(1) absorption of aqueous solutions prompt; absorption from repository preparations slow and sustained
(2) suitable for moderate volumes, oily vehicles or some irritating substances
(3) problematic in anticoagulated patients
(4) often the most painful route
(5) intermediate cost and requires trained administrators
(6) can cause elevation of laboratory tests, especially CK
Intravenous (IV) route:
(1) absorption complete or nearly so
(2) effects fast, potentially immediate
(3) useful in emergency situations
(4) relatively expensive and requires trained administrators
(5) permits titration of dosage due to ability to adjust dosing
(6) increased risk of adverse effects
(7) requires slow infusions usually
(8) suitable for large volumes
(9) irritating substance can be given if well diluted
(10) not suitable for oily or insoluble substances
