A route of administration is the way by which a drug, fluid, poison, or other substance is taken into the body.

Routes of administration are usually classified by application location. Routes of drug administration are the following:

1. Oral Route.

2. Sublingual Route

3. Intravenous Route

4. Intramuscular Route

5. Subcutaneous Route

6. Inhalation Route

7. Nasal Route

8. Rectal Route

9. Cutaneous Route

10. Ear Route

11. Ocular Route

1. Oral route:

The drug is administered to or by way of the mouth.1 A drug given via this route is absorbed into the systemic circulation from the gastrointestinal tract. The oral route is the most frequently used route for drug administration.

 Solid dosage forms : 

tablets (immediate-release, enteric-coated, modified-release), capsules, granules, powders

Liquid dosage forms e.g. syrups, elixirs, suspensions

 Advantages of the Oral Route:

• Cheap

• Generally safe route of drug administration

• Simple and convenient for the patient

• The patient can self-administer

• Non-invasive

 Disadvantages of the Oral Route:

• Drug absorption may vary.

• Subject to first-pass metabolism

• Oral route not possible in unconscious patients

• Unsuitable in patients who are vomiting

• Slow onset of action

• The drug may be destroyed by digestive enzymes and/or stomach acid

2. Sublingual Route:

A dosage form designed for the sublingual (SL) route is administered under the tongue. The drug is absorbed from the blood vessels that lie under the tongue and enters the systemic circulation directly, thus avoiding first-pass metabolism.

 Sublingual Dosage Forms:

Sublingual tablets e.g. glyceryl TRI nitrate SL tablet Sublingual films e.g. Suboxone SL film Sublingual sprays e.g. glyceryl TRI nitrate SL spray

 Advantages of the Sublingual Route:

• Rapid drug absorption

• Quick onset of action

• Avoids first-pass metabolism

• The patient can self-administer

• Convenient for the patient

• Can be quickly terminated by spitting out the sublingual tablet if required

• This route can be used by people who have difficulty swallowing tablets,

 Disadvantages of the Sublingual Route:

• Most drugs are not available as sublingual formulations

• The taste of the sublingual dosage form may not be liked by the patient

• Placing the sublingual dosage form under the tongue until it dissolves may be considered inconvenient by some patients.

• Irritation to the oral mucosa

3. Intravenous Route:

A drug administered by the intravenous (IV) route is given directly into a vein as a direct injection or infusion.

 Intravenous Dosage Forms:

• Injection

• Emulsion injection

• Solution for injection

• Solution for infusion

 Advantages of the Intravenous Route:

• Immediate effect (suitable for emergencies)

• Can be given to unconscious patients

• Avoids first-pass metabolism

• Achieves predictable and precise control over drug plasma levels compared to other routes

 Disadvantages of the Intravenous Route:

• Possible anaphylaxis

• Risk of infection

• Inconvenient to the patient

• Painful

• Expensive compared to other routes

• Requires trained medical/nursing staff to administer

4. Intramuscular Route

The intramuscular (IM) route is given directly into the muscle.

 Intramuscular Dosage Forms:

• Solution for intramuscular injection

 Advantages of the Intramuscular Route:

• Immediate onset

• Depot or sustained release

• Avoids first-pass metabolism

 Disadvantages of the Intramuscular Route:

• Expensive

• Requires trained medical/nursing staff

• Irritating drugs may be painful

• Slower onset than the IV route

• Variable drug absorption dependent upon the muscle group used and the blood flow to the muscle

5. Subcutaneous Route:

The subcutaneous (SC) route is injected into the subcutaneous tissue. It can be given as a direct injection or infusion.

 Advantages of the Subcutaneous Route:

• Can be self-administered by the patient

• Some drugs have a long duration of action

• Low risk of systemic infection

 Disadvantages of the Subcutaneous Route:

• Variable drug absorption dependent on blood flow

• Only a small volume of the drug can be administered

6. Pulmonary/Inhalation Route

The inhalation route is used for a local effect or systemic effect. The drug is inhaled through the mouth and delivered into the lungs.

 Pulmonary Dosage Forms:

• Metered-dose inhalers

• Dry powder inhalers

 Advantages of Inhalation Route:

• Rapid onset of action

• Systemic side effects minimized 

• Reaches the site of action

 Disadvantages of the Inhalation Route:

• Proper inhaler technique required for the drug to work maximally

• Only a few, drugs can be given via this route

• May stimulate the cough reflex

7. Nasal Route

Administration of a drug directly into the nose.

 Nasal Dosage Forms

• Nose spray

• Nose drops

 Advantages of Nasal Route:

• Can be self-administered by the patient

• Rapid onset of action

• Minimal side effects

 Disadvantages of Nasal Route:

• Some nasal drops or sprays may lead to an unpleasant taste in the mouth

8. Rectal Route

Administration into the rectum for a localized effect or a systemic effect.

 Rectal Dosage Forms:

• Suppositories

• Enemas

 Advantages of Rectal Route:

• The patient can self-administer

• Can be used for a local effect

• Can be used in patients unable to swallow, vomiting, or unconscious

• Reduced first-pass metabolism

 Disadvantages of Rectal Route:

• Uncomfortable and messy to use

• Inconvenient for the patient

• Absorption can be slow and erratic

• Not well accepted by the patient

9. Cutaneous Route Administration to the skin.

 Cutaneous Dosage Forms

• Dermatological preparations e.g. ointments, creams, liquids, powders, solutions, shampoos

 Advantages of Cutaneous Route

• The patient can self-administer

• Can be used for a localized effect

• Systemic side effects/drug interactions avoided or reduced,

 Disadvantages of Cutaneous Route

• Some preparations may be messy or difficult to apply

• Some dermatological preparations are time-consuming to apply

10. Ear Route

Administration to or by way of the ear.

 Ear Dosage Forms:

• Ear drops

 Advantages of the ear Route:

 Disadvantages of the ear Route:

• May be difficult for some patients to administer themselves

• This route may be considered time-consuming by the patient, as they need to remain on their side/tilt the ear for a few minutes after the instillation of ear drops

11. Ocular/Eye Route:

Administration of drugs into the eye.

 Ocular Dosage Forms:

• Eye ointment

• Eye drops

 Advantages of the Ocular Route:

• Convenient for the patient

• Systemic side effects reduced

 Disadvantages of the Ocular Route:

• May cause temporary blurring of vision upon instillation of eye drops/ointment

• Barriers to administration e.g. poor manual dexterity, poor vision

• Not all ocular dosage forms can be used with contact lenses.