3.3.3 Administration Methods
The speed of onset and duration of action for any opioid depend on the specific
drug chosen and its formulation (tablet, elixir, etc.). Most are well absorbed
after oral or rectal administration, yet absorption may not be complete.
Further, drugs absorbed from the gut are subject to first-pass metabolism in
the liver and, hence, should be given at higher doses than when given
parenterally. Although dosage requirements for different parenteral routes
(intravenous, subcutaneous, and intramuscular) are comparable or equivalent,
the onset of drug action is typically most rapid after intravenous dosing
because there is no delay in absorption. Therefore, drug dose and frequency
should be titrated to the individual patient's response and analgesic needs
when changing the route of administration or the type of formulation.
Tolerance and Physical Dependence
Bisphosphonates and Calcitonin