Routes of drug administration عملي

Factors to be considered when choosing certain route:
1. Site of drug action: e.g., treatment of certain GIT diseases necessitates giving the drug orally.
2. Drug nature: intravenous fluids should be isotonic.
3. Onset of action: treatment of emergency conditions necessitates the use of intravenous route.
4. Duration of action: drugs intended for longer duration of action are given by a route when absorption is slow.
5. Patient status: oral route can not be used when the patient is unconscious, or has difficulty in swallowing, or has repeated vomiting.
6. Desire of the patient.

Routes of administration can be classified as follows:
A. Enteral (GIT): oral, sublingual, and rectal.
B. Paranteral: IM, IV, ID, SC, inhalation, topical, and others

Enteral:
1. Oral: the most common route. Ideally swallowing a solid dosage form should be followed by drinking 150 ml of water while the patient in standing position.

Advantages:
a) Simple, convenient, and acceptable.
b) Oral drugs can be given in different dosage forms.
c) Safe route: since in overdose, it can be managed easily.
Disadvantages:
a) Some drugs are destroyed in the gut (e.g., some penicillins, insulin, oxytocin)
b) Some drugs may cause gastric irritation.
c) Absorption may be affected by food or by other drugs which inhibit gut motility e.g., antimuscarinics and opiods.
d) First pass metabolism (by intestinal wall and by the liver) limits the efficacy of some drugs when taken orally.