Parenteral Route (Injection)
The parenteral route involves giving a drug by
injection, directly into the body tissues or bloodstream, bypassing the
digestive system. This route is used when a rapid, accurate, or
controlled drug effect is needed, or when the drug cannot be given orally
because it would be destroyed in the stomach or not absorbed properly.
Definition
The parenteral route of administration refers to
giving a drug through a needle and syringe into the body fluids or
tissues, such as veins, muscles, or under the skin. It provides fast and
effective drug action.
Types of Parenteral Routes
- Intravenous
(IV): Injected directly into a vein for immediate action.
Example: Glucose injections, antibiotics, saline infusions. - Intramuscular
(IM): Injected into a muscle (like deltoid or gluteus) for moderate
and sustained action.
Example: Vaccines, vitamin B12 injection. - Subcutaneous
(SC): Injected under the skin for slow and prolonged absorption.
Example: Insulin, heparin. - Intradermal:
Injected into the skin layer for testing and diagnostic purposes.
Example: Tuberculosis test, allergy tests.
Advantages
- Provides
rapid onset of action, useful in emergencies.
- Ensures
100% bioavailability (entire drug reaches circulation).
- Can be
used for unconscious or vomiting patients.
- Avoids
destruction by stomach acid or enzymes.
- Allows
accurate dose control.
- Suitable
for poorly absorbed or irritant drugs.
- Can
provide sustained or controlled release through depot injections.
Disadvantages
- Painful
and may cause tissue irritation or infection.
- Requires
trained personnel for administration.
- More
expensive and needs sterile equipment.
- Once
injected, the dose cannot be removed or reversed.
- Not
suitable for self-administration (except insulin).
- May
cause injury to nerves or blood vessels if not done properly.
Importance of Parenteral Route
- Ensures
fast and reliable drug action in critical conditions:
Drugs given by injection enter the bloodstream directly, producing a quick response which is vital in emergencies.
Example: Adrenaline injection is used immediately during severe allergic reactions (anaphylaxis). - Useful
when oral route is not possible (e.g., unconscious, vomiting, or fasting
patients):
When patients cannot swallow or retain medicines, the parenteral route ensures drug delivery.
Example: Intravenous glucose is given to unconscious diabetic patients with low blood sugar. - Provides
precise control over drug dosage and blood levels:
Injections allow accurate adjustment of drug concentration in the body, which is important for critical care.
Example: Insulin injection helps control blood glucose levels precisely in diabetic patients. - Allows
use of drugs destroyed in the digestive system:
Some medicines cannot be given orally because they get broken down by stomach acid or digestive enzymes.
Example: Penicillin G is given by injection because it is destroyed by gastric acid. - Suitable
for large-volume fluids, like glucose or electrolyte infusions:
Fluids needed for hydration, nutrition, or electrolyte balance can be given directly into the bloodstream.
Example: Normal saline or 5% dextrose IV infusions are commonly used in hospitals. - Depot
injections offer long-lasting effects, reducing dosing frequency:
Certain formulations release the drug slowly over time, maintaining a prolonged effect.
Example: Depo-Provera (medroxyprogesterone acetate) injection provides birth control for 3 months. - Essential
in hospital and emergency care for life-saving treatments:
Many emergency medicines must act quickly and effectively, which is only possible through injection.
Example: Intravenous morphine for severe pain or IV antibiotics for serious infections.
