Routes of Drug Application

• Routes of drug application are divided based on the targeted purpose and the condition of the intended site of action.
• The two categories are Local Application and Systemic Application.
• The choice of administration route depends on the drug and patient factors.

Application place of drugs

• For drugs to be effective, they must be present at a specific concentration at the site of action.
• This concentration is called MEK or minimum effective concentration.
• When administering medication, the amount and application site must ensure that the active substance reaches MEK at the needed site.

Local Application Routes

• Place of effect is on the body surface.

• Routes include:

  • Epidermal
  • Intracutaneous
  • Intrathecal
  • Intrapleural
  • Intraperitoneal
  • Intracardiac
  • Intraarticular
  • Intrauterine
  • Intravaginal
  • Into the rectum and colon
  • On the conjunctiva
  • Intranasal and buccal

Epidermal

• Used for localized lesions in accessible areas.
• Appropriate for drugs with minimal or no absorption.
• Characterized by minimal systemic side effects or toxicity.

Intracutaneous (into the skin)

• Applied to the dermis layer, located just below the epidermis.
• Sterile solutions and test serums for allergy and bacteriology tests are administered this way.

On the Conjunctiva

• Used to treat various eye infections.
• Ophthalmic preparations must be sterile.
• Ophthalmic preparations are called 'colir'.

Intranasal application

• Used for diseases of the nasal mucosa and paranasal sinuses.
• Drugs include anti-inflammatories, vasoconstrictors and local anesthetics.
• Systemic application is also possible

Buccal (intraoral)

• Used for infections of the mouth and gums.

External Ear Canal

• Via medication to treat some diseases of the outer ear canal or eardrum.

Intrathecal

• Sterile antibiotic or local anesthetic solutions are used
• Used this way to create a local effect on the meninges or spinal nerve roots.

Intracardiac

• Used in emergency situations or for cardiac resuscitation during cardiac surgery. Stimulant drugs like adrenaline can be administered directly to the heart.

Intraperitoneal:

• Used in some cases of inflammation of the peritoneum.
• Injections are made into the abdominal cavity.

Intraarticular:

• In some joint diseases, corticosteroids or antibacterial drugs can be injected directly into the joint.

Rectal and Colonic

• Suppository, enema or ointment-shaped preparations are administered via the rectum or colon.
• Treatment includes superficial lotions of the rectum, hemorrhoids, and some diseases of the colon.

Intrauterine

• Oxytocic hormone is injected into the myometrium.
• Accelerates uterine contraction after cesarean sections and reduces bleeding.

Intravaginal

• Medications are administered into the vagina using a pessary.
• Spermicide drugs in foam and gel forms are used to prevent pregnancy.

Systemic Drug Application Methods

• Includes Enteral, Parenteral, Transdermal, and Inhalation administrations.

Enteral

• Route of administration via oral, sublingual, or rectal.

Parenteral

• Administration of drugs that bypass the gastrointestinal tract.
• Drugs are injected into a vein or tissue using a sterile syringe.
• Includes intravenous, subcutaneous, intramuscular, and bone marrow injections.
• This route allows drugs to start working quickly.

Transdermal

• Application of drugs to the skin in a special pharmaceutical form.
• Allows the drug to be absorbed from the skin and enter the circulation.

Inhalation

• Lipophilic drugs in gas or vapor form pass through the alveolar membrane.
• Enters the general blood circulation through inhalation.

Oral Route

• Drugs are swallowed.
• The most commonly used, most practical, and most economical route.
• Drugs must pass through the liver after absorption before entering systemic circulation; some drugs are inactivated.
• Absorption may not be complete.

Sublingual Route

• Drug effect is desired to start rapidly.
• The drug quickly dissolves.
• Allows an effect with small amounts.
• Utilizes drugs highly soluble in fat.
• Administered by placing small tablets (e.g., nitroglycerin, nifedipine) under the tongue.

Rectal Administation

• A local or systemic effect is achieved via absorption from the rectal mucosa.
• Administered in the form of suppositories or enemas.
• Commonly used for patients unable to take oral medication or for infants.

Parenteral Administration

• Used when drugs cannot be sufficiently absorbed or broken down in the gastrointestinal tract upon oral administration.
• Used when drugs require rapid onset of action in emergency situations.
• Necessary when a patient is unconscious, unable to swallow, or experiencing nausea, vomiting, or diarrhea.

Disadvantages of Parenteral Administration

• Can be painful.
• May cause vascular or tissue damage.
• Creates psychological stress.
• Requires administration by someone other than the patient.
• The pharmaceutical form can be expensive.

Intravenous (IV) Administration

• Only water-soluble or water-mixable drugs can be administered.
• Preferred when a rapid effect is desired, or if the patient is unconscious.
• Bioavailability is usually 100%.
• Drug solutions up to 10 ml are injected in 1-2 minutes.
• Intravenous infusion involves the slow administration of large volumes of drug solutions over 1-2 hours into a vein.

Disadvantages of IV Administration

• Only water-soluble drugs can be administered.
• Oily solutions and suspensions cannot be administered intravenously, to avoid embolism.
• Drugs with low water solubility may precipitate in the vein if injected rapidly.
• Administered drug cannot be retrieved.
• Presents a high risk of anaphylaxis (severe allergic reaction).
• Is an irritant, and may cause tissue damage if extravasation occurs.

Intramuscular (IM) Administration

• Drug is injected into an appropriate muscle, like the gluteal or deltoid.
• The volume of solution should not exceed 5 ml.
• Absorption is primarily affected by blood flow in the injection area.
• Absorption is increased by massage or exercise.

Subcutaneous Administration

• Administered under the skin, often on the outer surface of the humerus or femur region.
• A maximum of 2 ml of solution should be applied to avoid pain.
• Irritant drugs should be applied intramuscularly rather than subcutaneously.
• Implants or pellets of some drugs (e.g., compressed tablets) are placed under the skin for slow and regular release.

Intraosseous Injection

• Used in infants and adults when veins cannot be found.
• Involves injecting the drug into a suitable bone marrow (sternum).
• Drug then passes rapidly into the blood.
• A very rare method.

Transdermal Administration

• Applies the drug to the skin surface for a systemic effect.
• Requires highly lipophilic and small-dose effective drugs (e.g., nitroglycerin, scopolamine, clonidine, fentanyl, testosterone).
• Uses a transdermal therapeutic system, (patch).

Inhalation Application

• Alveoli provide a large surface area with a highly permeable membrane.
• High blood flow rate in the lungs.
• Inhaled drugs quickly pass through the alveolar membrane and enter the bloodstream.
• Includes gaseous and vaporous drugs (e.g., sevoflurane) and those with high fat solubility (e.g., general anesthetics, nitrous oxide).
• Common for drugs treating asthma and COPD.

Application Areas and Pharmaceutical forms table

• Lists Local and Systemic application forms
• Details common pharmaceutical forms
• Provides examples of pharmaceutical forms for common applications