Routes of Drug Administration Flashcards
Prof. Soremekun
What are the two major classifications of drug administration route?
i. Enteral e.g. oral, rectal.
ii. Parenteral e.g. IM, IV, SC, ID
The choice of route depends on
convenience and expedience
What is parenteral route?
By definition, parenteral drug administration refers to drugs given by routes other than the digestive tract.
In common medical usage, the term excludes topical and inhalation administration and includes only the various hypodermic routes e.g. IV, IM, SC,
Drug absorption from parenteral sites is determined by ________
i. The physiochemical properties of the drug
ii. The dosage form
iii. Certain physiologic and anatomic factors.
Most drug solutions should be injected over a 1-2 minutes period.
True or False?
True.
This is to avoid excessively high drug concentrations in the blood and other highly perfused tissues immediately after the injection.
There is no absorption involved in the pharmacokinetic process of IV drugs.
True or False?
True.
No membrane is crossed hence no diffusion is required for absorption.
Usual dose of 150-250mg of phenytoin sodium should be injected at a rate not exceeding ______
50mg/min
What happens if an IV drug is injected too rapidly?
The drug may be precipitated in the vein if injected too rapidly and may cause damage to the veins (phlebitis)
Mention 3 advantages of IV administration.
- It is produces rapid response
- The whole dose is delivered to the blood stream. Hence more bioavailability.
- Veins are relatively insensitive to irritant drugs
Mention 4 disadvantages of IV administration.
- It may be difficult to find a suitable vein
- There is risk of toxicity
- Requires a trained personnel
- Greater cost of preparation
- Insoluble materials e.g. drug suspensions cannot be given by intravenous route because they may cause embolism
What are the 3 commonly used sites for IM administration?
i. The arm (deltoid) - highest vascularity
ii. The thigh (vastus lateralis)
iii. The buttocks (gluteus maximus)
Mention 5 factors that influence absorption from the IM sites.
i. Vascularity of the injection site (most important)
ii. Ionisation degree of the drug
iii. Lipid solubility of the drug
iv. Volume of injection
v. Osmolality of the solution
Mention 3 advantages of IM administration.
- Absorption by IM route is relatively fast
- It is used when prompt (not immediate) effect is required.
- It is easier to administer than IV.
Mention 5 disadvantages of IM administration.
- More painful than I.V.
- Does not always assure rapid or complete absorption
- Drug may precipitate at injection site, especially for poorly soluble drugs (e.g. phenytoin, digoxin, diazepam).
- The solvent may be absorbed faster than the drug causing precipitation at site of injection
- Irritation around injection site is common
When is the SC route preferred?
The route is usually chosen when a slower rate of absorption is required, in order to avoid:
- Too intense a response
- Too short a response
- Frequent injections