Drug Application Routes

• Routes of drug application are divided based on the drug's target and the condition of the intended site of effect.
• Key factors in the choice of administration route include the specific drug and patient considerations.

Application Places of Drugs

• Drugs must reach a certain concentration called MEK (minimum effective concentration), to be effective in a specific area.
• The quantity and site of administration need to be determined such that the active substance reaches its intended effect in MEK.

Local Application Routes

• Local application involves applying the drug to the body's surface.
• Specific local application routes are:
  • Epidermal
  • Intracutaneous
  • Intrathecal
  • Intrapleural
  • Intraperitoneal
  • Intracardiac
  • Intraarticular
  • Intrauterine
  • Intravaginal
  • Into the rectum and colon
  • On the conjunctiva
  • Intranasal and buccal

Epidermal Route

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

Intracutaneous Route (into the skin)

• Applied to the dermis layer, just below the epidermis.
• Sterile solutions and test serums for allergy and bacteriology tests use this method.

Conjunctiva Application

• Used for various eye infections.
• Ophthalmic preparations are called 'colir'.
• Preparations must be sterile.

Intranasal Application

• Used for diseases of the nasal mucosa & paranasal sinuses.
• Anti-inflammatory, vasoconstrictor, and local anesthetic drugs are administered this way.
• Systemic application is possible.

Buccal (Intraoral) Application

• Used for mouth and gum infections.

External Ear Canal Application

• Used in some diseases of the external ear canal or eardrum.

Intrathecal Application

• Sterile antibiotic or local anesthetic solutions are administered to create a local effect on the meninges or spinal nerve roots.

Intracardiac Application

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

Intraperitoneal Application

• Injections can be made into the abdominal cavity in some cases of inflammation of the peritoneum.

Intraarticular Application

• Corticosteroids or antibacterial drugs can be injected into the joint in some joint diseases.

Rectal and Colonic application

• Suppository, enema, or ointment-shaped preparations are used.
• Used for superficial conditions of the rectum, hemorrhoids, & some diseases of the colon.

Intrauterine Application

• Oxytocic hormone is injected into the myometrium to accelerate uterine contraction after cesarean sections, thus reducing bleeding.

Intravaginal Application

• Medications are usually administered into the vagina in the form of pessaries.
• Spermicide drugs in foam & gel forms are also used to prevent pregnancy.

Systemic Application Methods

• Systemic application introduces the drug into the body's circulation.
• Main systemic application methods are:
  • Enteral (oral, sublingual, rectal)
  • Parenteral (intravenous, subcutaneous, intramuscular, into the bone marrow)
  • Transdermal
  • Inhalation

Enteral Application

• Includes oral, sublingual, and rectal routes.

Parenteral Application

• Involves administering drugs not absorbed from the gastrointestinal tract or broken down there.
• Injected into a vein or tissue with a sterile syringe for quick action.

Transdermal Application

• Application of a drug to the skin in a special pharmaceutical form.
• Ensures drug absorption from the skin into the circulation.

Inhalation Application

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

Oral Route (per os, by mouth)

• Most commonly used, most practical, and economical.
• Drugs must pass through the liver post-absorption prior to entering the systemic circulation.
• Some drugs may be inactivated, and absorption may be incomplete.

Sublingual Route

• Used when a quick drug effect is desired.
• Properties of this route are:
  • Quickly dissolving.
  • Able to create an effect with small amounts.
  • Highly soluble in fat.
• Administered via small tablets, such as nitroglycerin and nifedipine.

Rectal Administration

• Local or systemic effects can be achieved by absorption from the rectal mucosa.
• Drugs administered via suppositories or enemas.
• Method often used for patients unable to take oral medication and in infants.

Parenteral Administration

• Used when drugs cannot be absorbed or broken down sufficiently from the gastrointestinal tract, or in emergency situations.
• Used when the patient is unconscious, unable to swallow or experiencing nausea, vomiting, or diarrhea.

Parenteral Administration Disadvantages

• Painful
• May cause vascular or tissue damage
• Creates psychological stress
• Cannot be self-administered
• May be expensive based on the pharmaceutical form utilized.

Intravenous (IV) Administration

• Only water-soluble or water-mixable drugs can be administered.
• Used when rapid effect is desired.
• Bioavailability is usually near 100%.
• Typically, drug solutions up to 10 ml are injected within 1-2 minutes.
• Intravenous infusion involves the slow administration of large volumes of drug solutions (over 1-2 hours) into a vein.

Intravenous Administration Disadvantages

• Only water-soluble drugs can be administered.
• Oily solutions and suspensions are not administered intravenously due to risk of embolism.
• Drugs with low water solubility may precipitate if injected rapidly (e.g., diazepam, 5 mg/min).
• Anaphylaxis is a high risk.
• The administered drug cannot be retrieved.
• Irritant drugs can cause tissue damage if extravasation occurs.

Intramuscular (IM) Injection

• Involves injecting the drug into the appropriate muscle tissue.
• The Gluteal or deltoid muscle is often preferred.
• Solution volume should not exceed 5 ml.
• The absorption of the injected drug is mostly affected by blood flow in the injected area.
• Massage or exercise increases absorption.

Subcutaneous Injection

• Injected "under the skin"
• The outer surface of the humerus or femur region is often preferred.
• A maximum of 2 ml of solution should be applied to prevent pain on the skin
• Irritant drugs should be applied intramuscularly rather than subcutaneously
• Some drugs are placed under the skin in the form of implants or pellets (such as compressed tablets), so that the drug is released slowly and regularly,
• Provides a long-lasting effect

Intraosseous Injection

• Used in infants and sometimes adults if veins cannot be located.
• The drug is injected into a suitable bone marrow (sternum).
• Passes rapidly into the blood.
• A very rare method.

Transdermal Application

• Application of a drug to the skin surface to acheive a systemic effect
• Key features:
  • Highly lipophilic
  • Small Dose
  • Effective drugs, such as nitroglycerin, scopolamine, clonidine, fentanyl, and testosterone.
• A transdermal therapeutic system (patch) is applied to the skin

Inhalation Application

• It is advantageous in that the alveoli have a very large surface area and a highly permeable membrane, and that the blood flow rate in the lungs is also very high.
• When inhaled, they quickly pass through the alveolar membrane in the lungs and enter the bloodstream.
• Drugs that are gaseous and vaporous (sevoflurane)
• Drugs that have high fat solubility (nitrous oxide, asthma and COPD drugs)

Application areas of drugs and pharmaceutical forms specific to these areas (local)

• Epidermal (on the skin)- Ointment, pomade, cream, lotion, powder, soap, solution, liniment, plaster, paste
• Intranasal - Nasal drops and nasal spray
• Intravaginal - Vaginal suppository, vaginal tablet, ointment, gel, foam
• Buccal (inside the mouth) - Lozenge, solution, gargle
• Rectal - Ointment, suppository, enema
• Colon - Enema
• External ear canal - Otic (ear) drops

Application sites of drugs and pharmaceutical forms specific to these sites (systemic)

• Oral - Tablet, dragee, capsule, film-coated tablet, enteric tablet, chewable tablet, packet, effervescent tablet, cachet, pill, syrup, elixir, solution, suspension, drop, lotion, emulsion, extract
• Parenteral - Solution or suspension for injection, emulsion, implantation pellet
• Inhalation - Gas, vapor, aerosol, inhaler, nebulizer
• Transdermal - Patch, ointment
• Other - Nasal Spray