Routes of Drug Administration

• Routes of drug administration refers to how a drug is introduced into the body and subsequently enters the body.
• Drug administration is determined by the drug's properties and therapeutic objectives.
• Drug administration is classified by application location, also known as exposition.

Systemic vs. Local Administration

• Systemic administration: Drug is absorbed into the circulation and influences the entire body.
• Local administration: Drug is not absorbed into the circulation, affecting only the application site.

Systemic Enteral Administration

• Occurs through the gastrointestinal tract
• Includes oral, buccal, sublingual, and rectal routes

Oral Administration

• The drug is taken by mouth, swallowed, and then absorbed via the digestive tract.
• This is the most common, least expensive, and easily administered route.
• There can be limited absorption for some drugs, food affects absorption, patient compliance is needed, and drugs are metabolized before systemic absorption.

Buccal and Sublingual Administration

• Buccal: Medication is placed between the gum and cheek.
• Sublingual: Medication is absorbed under the tongue.
• Both routes bypass the first-pass effect and destruction by stomach acid.
• The pH of saliva is relatively neutral and Drug stability is maintained.
• This can cause immediate pharmacological effects.
• Suitable for certain drugs that can be taken in small doses; a portion may be lost if swallowed.

Rectal Administration

• Involves insertion of the drug into the rectum, where it is absorbed by the intestinal tract.
• Partially bypasses the first-pass effect and bypasses destruction by stomach acid.
• This route is ideal if the drug causes vomiting.
• Drugs may irritate the rectal mucosa, and it's not a well-accepted route.

First-Pass Effect

• The first-pass effect is when a drug is partially broken down by the liver before it reaches the bloodstream.

Systemic Parenteral Administration

• Involves direct administration into the systemic circulation
• It is useful for drugs poorly absorbed from or unstable in the GI tract
• Used for patients unable to take oral medications
• Provides the most control over the drug dose delivered to the body
• It can be irreversible and may cause pain, fear, local tissue damage, and infections

Injection

• Involves a small volume of liquid
• Intravenous (i.v.) administration leads to a quick onset of effect.
• Intramuscular (i.m.) and subcutaneous (s.c.) routes lead to gradual absorption into circulation.

Infusion

• Involves a large volume of liquid
• Includes parenteral nutrition, minerals, glucose, antibiotics (ATBs), and cytostatics.

Intravenous Administration (i.v.)

• It is the most common parenteral route.
• It's useful for drugs that are not absorbed orally.
• Permits rapid effect and maximum control over the amount of drug delivered.
• The drug is injected as a bolus and is delivered to the systemic circulation almost immediately.

Intramuscular Administration (i.m.)

• Drugs are in aqueous solutions that are absorbed rapidly.
• Specialized depot preparations allow slow absorption.
• Depot preparations consist of a drug suspension in a nonaqueous vehicle.
• The drug dissolves slowly, providing a sustained dose over an extended interval.

Subcutaneous Administration (s.c.)

• Provides absorption via simple diffusion, which is slower than the i.v. route.
• Minimizes the risk of hemolysis or thrombosis associated with i.v. injection.
• It provides constant, slow, and sustained effects.
• Avoid in instances where drugs cause tissue irritation due to the risk of severe pain and necrosis.

Topical Administration

• It is applied directly to and absorbed via the top layer of skin.
• It is for desired local skin effect.
• Note that transdermal application causes a systemic effect.

Inhalation

• Involves breathing a drug directly into the pathway to the lungs.
• Delivers medication directly to the lungs and is often used in pediatric patients for easier medication delivery.
• Medication has a lower strength than drugs delivered systemically, resulting in fewer side effects.

Otic Administration

• It involves administering a drug into the ear canal.
• Typically used for the specific site.

Conjunctival Administration

• Involves administering medication to the outer layer covering the eye and eyelid.
• Provides maximum absorption directly by that site.

Nasal or Intranasal Administration

• Delivers medication via the nostril
• Offers easy administration and direct access to the bloodstream without intravenous access
• Note that it may have a systemic effect