Local Drug Application

• Drugs must be present at a certain concentration in order to have an effect at a certain place.
• This concentration is called MEK (minimum effective concentration).
• When administering drugs, amounts and application sites must be determined, so the active substance reaches the place of effect in MEK.
• Routes of drug application are divided into 2 according to:
  • Purpose targeted by specific drug
  • Condition/part of body the drug is intended to affect
• Choice of administration route depends on drug and patient factors.

Local Application Ways

• The place where the drug is intended to affect should be on the body surface.
• Consists of epidermal, intracutaneous, intrathecal, intrapleural, intraperitoneal, intracardiac, intraarticular, intrauterine, intravaginal, into the rectum and colon, on the conjunctiva, intranasal, and buccal.

Epidermal Route

• Treatment for localized lesions in accessible areas.
• Used for drugs that have minimal or no absorption.
• There are no or minimal systemic side effects or toxicity.

Intracutaneous (into the skin) Route

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

Conjunctiva Route

• Used in various infections.
• Ophthalmic preparations used, also called 'colir'.
• They must be sterile.

Intranasal Application

• Treats diseases of the nasal mucosa and paranasal sinuses.
• Uses anti-inflammatory, vasoconstrictor, and local anesthetic drug solutions.
• Systemic application is also possible.

Buccal (intraoral) Route

• Used for mouth and gum infections.

External Ear Canal Route

• Treats some diseases of the external ear canal or eardrum with medication applied this way.

Intrathecal Route

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

Intracardiac Route

• Used in emergency situations or for cardiac resuscitation.
• Stimulant drugs like adrenaline are administered directly to the heart.

Intraperitoneal Route

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

Intraarticular Route

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

Rectal and Colonic application

• Suppository or enema and ointment-shaped preparations used for superficial lotions of the rectum, hemorrhoids, and some diseases of the colon.

Intrauterine Route

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

Intravaginal Route

• Medications are usually administered into the vagina in the form of a pessary.
• Spermicide drugs in the form of foam and gel are also used to prevent pregnancy.

Systemic Drug Application Methods

• Enteral (oral, sublingual, rectal)
• Parenteral (intravenous, subcutaneous, intramuscular, into the bone marrow).
• Transdermal
• Inhalation

Enteral Route

• Administration of drugs that are not absorbed from the gastrointestinal tract or broken down in a vein or tissue with a sterile syringe.
• It starts to work quickly.

Transdermal Route

• Application of the drug to the skin in a special pharmaceutical form so it is absorbed from the skin and enters the circulation.

Inhalation Route

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

Oral Route

• This most commonly used, most practical, and most economical route.
• Problems compared to the parenteral route:
  • Since drugs are used orally, must pass through the liver after absorption before entering the systemic circulation.
  • Some drugs may be inactivated, and absorption may not be complete.

Sublingual Route

• Used in cases where the drug effect is desired to start very quickly.
  • Quickly dissolving
  • Can create an effect with small amounts
  • Highly soluble in fat
• Drugs in the form of small tablets (such as nitroglycerin and nifedipine) are administered this way.

Rectal administration

• Applying drugs to the rectum achieves either a local or systemic effect with absorption from the rectal mucosa.
• Drugs can be administered in the form of suppositories or enemas.
  • Method used in patients who cannot take oral medication and in infants.

Parenteral Administration

• Used for drugs that cannot be absorbed or broken down in sufficient amounts from the gastrointestinal tract when administered orally.
• Used for drugs that require rapid onset of effect, commonly used in emergencies.
• Used for patients who are unconscious, unable to swallow, or are experiencing nausea, vomiting, or diarrhea.

Disadvantages of Parenteral drug administration

• Painful
• Can cause vascular or tissue damage
• Creates psychological stress
• Cannot be administered by the patient alone
• Disadvantages: Expensive pharmaceutical form used

Intravenous (IV) Route

• Only drugs that are water-soluble or water-mixable can be administered this way.
• Choice when rapid effect is desired.
• If the patient is unconscious and cannot swallow the drug, this application is preferred.
• Bioavailability is usually 100%.
• Drug solutions up to 10 ml are injected in 1-2 minutes.
• Intravenous infusion is the slow administration of large volumes of drug solutions (over 1-2 hours) into a vein.

Disadvantages of the intravenous (IV) Route

• Only water-soluble drugs can be administered.
• Oily solutions and suspensions are not administered intravenously due to embolism.
• Drugs with low water solubility may precipitate in the vein if injected rapidly (diazepam, 5 mg/min).
• Administered drug cannot be retrieved.
• High risk of anaphylaxis
• Irritant drugs may cause tissue damage if extravasation occurs.
• Anaphylaxis is a severe allergic reaction.

Intramuscular (IM) Route

• Injecting the drug into the appropriate muscle tissue. -Gluteal or deltoid muscle is usually preferred. -The volume of solution administered should not exceed 5 ml.
• Absorption of the injected drug is mostly affected by the blood flow in that area.
• Massage or exercise increases absorption.

Subcutaneous Route

• Inserted under the skin, outer surface of the humerus or femur region is often preferred.
  • Maximum of 2ml 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 the drug is released slowly and regularly.
  • Providing a long-lasting effect.

Intraosseous injection

• For infants and adults: If veins cannot be found, the drug is injected into a suitable bone marrow (sternum), from there it passes rapidly into the blood.
• This is a very rare method.

Transdermal Route

• The application of the drug to the skin surface for systemic effect.
  • Highly lipophilic and small dose
  • Effective drugs (such as nitroglycerin, scopolamine, clonidine, fentanyl, testosterone) are applied this way.
• Use a transdermal therapeutic system (patch).

Inhalation Route

- The alveoli have a very large surface area and a highly permeable membrane, and 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) and have high fat solubility, such as general anesthetics (nitrous oxide) and asthma and COPD drugs, are administered this way.

Application Areas of Drugs and Pharmaceutical Forms Based on Local application

• Epidermal on the skin uses: ointment, pomade, cream, lotion, powder, soap, solution, liniment, plaster, or paste
• Intranasal route uses: Nasal drops and Nasal spray
• Intravaginal route uses: Vaginal suppository, vaginal tablet, ointment, gel, or foam
• Buccal route uses: lozenge, solution, or gargle
• Rektal route uses: Ointment, suppository, enema.
• Kolon route uses: Enema
• Dış kulak yolu, Otic (ear) drops (solution, suspension)

Pharmaceutical Forms based on Systemic application

• Oral (ağızdan) applications uses : Solid Forms: tablet, dragee, capsule, film-coated tablet, enteric tablet, chewable tablet, packet, effervescent tablet, cachet, or pill
• Uses : Liquid Forms: Syrup, elixir, solution, suspension, drop (concentrated solution), lotion, or emulsion
• Parenteral(sc, im, iv) route uses: Solution or suspension for injection, emulsion (ampoule, vial, powder for reconstitution), implantation pellet
• Inhalation route uses: Gas, vapor, aerosol, inhaler, or nebulizer
• Transdermal route: Patch (TTS) or ointment. Other routes :Nasal spray