Various route of Drug administration

Various route of administration

The path taken by the drug to get into the body is known as the route of drug administration. A drug may be in ionized or unionized form.

Classification:
1. Enteral route
2. Parenteral route
3. Inhalation
4. Topical

1. Enteral Route:
Enteral route is through the alimentary canal. It might be:
A. Oral
B. Sublingual
C. Per rectum

A. Oral Route:
Oral route is the most common route of drug administration. It is mostly used for the neutral drugs. It may be in the form of tablets, capsules, syrup, emulsions or powders.

First Pass Effect:

First pass effect is the term used for hepatic metabolism of drug when absorbed and delivered through portal blood. Greater the first pass effect, less amounts of the drug reach the systemic circulation.

B. Sublingual Route:

Sublingual route involves tablets placed under the tongue or between cheeks or Gingiva. The drug should be lipid soluble and small.

Examples of drugs given by this route include nitroglycerin, isoprenaline and oxytocin. Nifedipine used for the treatment of hypertension in emergency is given by sublingual route. 

C. Rectal Route:

Drugs in solid forms such as suppositories or in liquid forms such as enema are given by this route. This route is mostly used in old patients. Drugs may have local or systemic actions after absorption.

Systemic acting drugs include Indomethacin (anti-inflammatory) and aminophyllin (bronchodilator). Retention enema is diagnostic and is used for finding the pathology of lower intestines. Drugs given by rectal route have 50% first pass metabolism.

Parenteral Route:

Parenteral route includes:

Injections:

1. Intra muscular

2. Intra venous

3. Intra-arterial

4. Intra-cardiac

5. Intra-thecal

6. Intraosseous- into bone marrow

7. Intrapleural

8. Intraperitoneal

9. Intra-articular

10. Intradermal (Intracutaneous)

11. Subcutaneous route (Hypodermic)

Site of Release:

Site of release may be intradermal, intraperitoneal, intrapleural, intracardiac, intra-arterial, intrathecal (into meninges of spinal cord), intra-articular (into joint cavity).

A. Subcutaneous: (under the skin)

Subcutaneous route might be used for the arm, forearm, thigh and subscapular space. The volume used is 2 ml. Insoluble suspensions like insulin and solids might be applied by this route. 

Examples of drugs given by subcutaneous route include insulin, adrenaline and Norplant. 

Hypospray/Jet Injection:

This method is needleless and is subcutaneous done by applying pressure over the skin. The drug solution is retained under pressure in a container called ‘gun’. It is held with nozzle against the skin. Pressure on the nozzle allows a fine jet of solution to emerge with great force. The solution can penetrate the skin and subcutaneous tissue to a variable depth as determined by the pressure. Mass inoculation is possible but the method is expensive, definite skills are required and cuts might result.

B. Intramuscular route:

Intramuscular route might be applied to the buttock, thigh and deltoid. The volume used is 3 ml. For example: Many vaccines, antibiotics, and long-term psychoactive agents. Recreationally the colloquial term 'muscling' is used.

 

C. Intravenous injections:

Intravenous injections might be applied to the cubital, basilic and cephalic veins.

For example: Many drugs, total parenteral nutrition.

 

D. Intraarterial route:

This method is used for chemotherapy in cases of malignant tumors and in angiography. 

For example: Vasodilator drugs in the treatment of vasospasm and thrombolytic drugs for treatment of embolism.

 

E. Intradermal route: (into the skin itself)

This route is mostly used for diagnostic purposes and is involved in:

 Schick test for Diphtheria

 Dick test for Scarlet fever

 Vaccines include DBT, BCG and polios skin.

 Sensitivity is to penicillin

 for skin testing some allergens, and also for mantoux test for Tuberculosis.

 

F. Intracardiac  route(into the heart)

Injection can be applied to the left ventricle in case of cardiac arrest. 

For example: Adrenaline during cardiopulmonary resuscitation (no longer commonly performed)

 

G. Intrathecal route:

Intrathecal route involves the subarachnoid space. Injection may be applied for the lumbar puncture, for spinal anesthesia and for diagnostic purposes. This technique requires special precautions. For example: Spinal anesthesia and chemotherapy.

 

H. Intra-articular route: (into an artery)

Intra-articular route involves injection into the joint cavity. Corticosteroids may be injected by this route in acute arthritis. For example:  Vasodilator drugs in the treatment of vasospasm and thrombolytic drugs for treatment of embolism.

 

I. Intraperitoneal route (infusion or injection into the peritoneum):

Intraperitoneal route may be used for peritoneal dialysis. For example: Peritoneal dialysis.

 

J. Intrapleural route:

Penicillin may be injected in cases of lung empyma by intrapleural route.

 

K. Injection into bone marrow

This route may be used for diagnostic or therapeutic purposes.

 

3. Inhalation:

Inhalation may be the route of choice to avoid the systemic effects. In this way drugs can pass directly to the lungs. Drugs used involve volatile drugs and gases. Examples include aerosols like salbutamol; steam inhalations include tincture and Benzoin

4. Topical route:

Drugs may be applied to the external surfaces, the skin and the mucous membranes. Topical route includes:

A. Enepidermic route

When the drug is applied to the outer skin, it is called enepidermic route of drug administration. Examples include poultices, plasters, creams and ointments.

B. Epidermic route (Innunition):

When the drug is rubbed into the skin, it is known as epidermic route. Examples include different oils.

C. Insufflations:

When drug in finely powdered form is blown into the body cavities or spaces with special nebulizer, the method is known as insufflations.

D. Instillation

Liquids may be poured into the body by a dropper into the conjunctival sac, ear, nose and wounds. Solids may also be administered.

E. Irrigation or Douching

This method is used for washing a cavity e.g. urinary bladder, uterus, vagina and urethra. It is also used for application of antiseptic drugs.

F. Painting/Swabbing

Drugs are simply applied in the form of lotion on cutaneous or mucosal surfaces of buccal, nasal cavity and other internal organs.