Routes of Drug Administration

Routes of Drug Administration

• Drugs must be administered to patients and absorbed to reach plasma levels.
• The route of administration depends on the drug's properties and the therapeutic objectives.
• Drug administration routes are classified by application location.

Systemic Administration

• The drug is absorbed into the circulation and influences the entire body.

Local Administration

• The drug is not absorbed into the circulation and affects only the application site.

Enteral Administration

• Through the gastrointestinal tract.

Oral Route

• Drugs are taken by mouth, swallowed, and absorbed via the digestive tract.
• This is often the most common and least expensive route, and can be easily administered.
• There is limited absorption of some drugs via the oral route.
• Food may affect absorption.
• Patient compliance is necessary.
• Drugs may be metabolized before systematic absorption.

Buccal Route

• Medication is placed between the gum and cheek.
• This bypasses the first-pass effects and destruction by stomach acid.
• Drug stability is maintained because the pH of saliva is relatively neutral.
• It may cause immediate pharmacological effects.

Sublingual Route

• Medication is absorbed under the tongue.
• This route is limited to certain types of drugs that can be taken in small doses.
• Part of the drug dose may be lost if swallowed.

Rectal Route

• Drugs are inserted into the rectum, where they are absorbed by the intestinal tract.
• It partially bypasses the first-pass effect.
• It bypasses destruction by stomach acid, which is ideal if the drug causes vomiting.
• Drugs may irritate the rectal mucosa.
• It is not a well-accepted route.

First-Pass Effect

• Refers to the metabolism of a drug before it reaches systemic circulation.

Parenteral Administration

• Directly into the systemic circulation.
• This route is used for drugs that are poorly absorbed from the GI tract or are unstable in the GI tract.
• It is suitable for patients unable to take oral medications.
• It provides the most control over the dose of drug delivered to the body.
• This route is irreversible and may cause pain, fear, local tissue damage, and infections.

Injection (Invasive)

• A non-physiological route of administration.
• It involves a small volume of liquid.
• Intravenous(i.v.) administration provides a quick onset of effect.
• Intramuscular(i.m.) and subcutaneous(s.c.) routes provide gradual absorption into the circulation.

Infusion

• Involves a larger volume of liquid.
• Used for parenteral nutrition, minerals, glucose, antibiotics (ATBs), cytostatics, etc.

Intravenous (i.v.) Route

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

Intramuscular (i.m.) Route

• Can be administered in aqueous solutions for rapid absorption or in specialized depot preparations for slow absorption.
• Depot preparations often consist of a suspension of drug in a nonaqueous vehicle.
• The drug dissolves slowly, providing a sustained dose over an extended interval.

Subcutaneous (s.c.) Route

• Provides absorption via simple diffusion and is slower than the i.v. route.
• Minimizes the risks of hemolysis or thrombosis associated with i.v. injection and may provide constant, slow, and sustained effects.
• Should not be used with drugs that cause tissue irritation, because severe pain and necrosis may occur.

Topical Route

• Applied directly to and absorbed via the top layer of the skin.
• Used for desired local skin effect.
• Transdermal applications have a systemic effect due to the drug's absorption into the bloodstream.

Inhalation

• The drug is breathed directly into the pathway to the lungs.
• Used for direct administration to the lungs.
• Used in pediatric patients for easier medication delivery.
• Medication has a lower strength than the same drug delivered by systemic routes, thus fewer side effects.

Otic Route

• Involves auricular administration via the ear canal.
• Typically used for the specific site.

Conjunctival Route

• Involves administering medication to the outer layer that covers the eye and eyelid.
• For maximum absorption directly to that site.

Nasal Route

• Administered nasally or intranasally.
• Ease of administration, direct access to the bloodstream without intravenous access.
• May have systemic effects.