Drug Application Routes and Sites

Application Places of Drugs

• For drugs to have an effect, they must be present at a certain concentration, known as MEK (minimum effective concentration).
• The amounts and application sites must be determined so the active substance reaches the place of effect in MEK.

Routes of Application

• Routes of application are divided into two types, based on the targeted purpose and the condition of the intended site.
• Choice of administration route depends on drug and patient factors.
• Local application affects the body surface.

Local Application Routes

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

Epidermal Application

• Used only for localized lesions in accessible areas.
• Administered only with drugs that have minimal or no absorption in those areas.
• Has minimal systemic side effects or toxicity.

Intracutaneous Application

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

Conjunctiva Application

• Used in various infections and involve the application of sterile ophthalmic preparations called "colir".

Intranasal application

• Used for treating diseases of the nasal mucosa and paranasal sinuses
• Delivers anti-inflammatory, vasoconstrictor, and local anesthetic drugs.
• Systemic application is also possible.

Buccal (Intraoral) Applications

• Used for mouth and gum infections.

External Ear Canal applications

• Delivers medication to treat some diseases of the external ear canal or eardrum.

Intrathecal Applications

• Administered with sterile antibiotic or local anesthetic solutions.
• Meant to create a local effect on the meninges or spinal nerve roots.

Intracardiac Applications

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

Intraperitoneal Applications

• Used in some cases of inflammation of the peritoneum; injections can be made into the abdominal cavity.

Intraarticular Applications

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

Rectal and Colonic Applications

• Involve the use of suppository or enema.
• Used for ointment-shaped preparations for superficial lotions of the rectum, hemorrhoids, and some diseases of the colon.

Intrauterine Applications

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

Intravaginal Applications

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

Systemic Drug Application Methods

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

Oral Administration

• Most commonly used, practical, and economical route.
• Orally administered drugs must pass through the liver after absorption, potentially leading to inactivation.
• Absorption may not be complete.

Sublingual Administration

• Used when a quick drug effect is needed.
• The drug is quickly dissolving
• Able to create an effect with small amounts
• Highly soluble in fat
• Drugs in the form of small tablets (such as nitroglycerin, nifedipine) are administered this way.

Rectal Administration

• Achieves either a local or systemic effect through absorption from the rectal mucosa.
• Drugs are administered in the form of suppositories or enemas.
• This method is more commonly used in patients who cannot take oral medication and in infants.

Parenteral Administration

• Used when drugs cannot be absorbed or broken down in sufficient amounts when administered orally.
• Used when drugs require rapid onset of effect, in emergency situations.
• Used when the patient is unconscious, unable to swallow, or experiencing nausea, vomiting, diarrhea, etc.

Disadvantages of Parenteral Administration

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

Intravenous (IV) Administration

• Administered with drugs that are water-soluble or water-mixable.
• Preferred in cases where a rapid effect is desired.
• Used when the patient is unconscious and cannot swallow the drug.
• 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 Intravenous (IV) Administration

• Only water-soluble drugs can be administered.
• Oily solutions and suspensions are not administered intravenously (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: severe allergic reaction

Intramuscular (IM) Administration

• Involves 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 blood flow in that area.
• Massage or exercise increases absorption.

Subcutaneous Administration

• The outer surface of the humerus or femur region is often preferred.
• The maximum dose 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.

Intraosseous Injection

• In infants and sometimes adults, if veins cannot be found.
• The drug is injected into a suitable bone marrow (sternum) and passes rapidly into the blood.
• A very rare method.

Transdermal Administration

• The application of the drug to the skin surface for systemic effect.
• Requires highly lipophilic and small dose effective drugs (such as nitroglycerin, scopolamine, clonidine, fentanyl, testosterone).

Inhalation

• Alveoli are advantageous because they have a very large surface area and a highly permeable membrane.
• The blood flow rate in the lungs is also very high.
• When inhaled, drugs pass through the alveolar membrane and enter the bloodstream quickly.
• Drugs that are gaseous and vaporous (sevoflurane) and have high fat solubility (such as general anesthetics like nitrous oxide) are administered through inhalation.

Application Areas and Forms (Local)

• Epidermal: 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: Lozenge, solution, gargle
• Rectal: Ointment, suppository, enema
• Colon: Enema
• External ear: Otic (ear) drops (solution, suspension)

Application Sites and Pharmaceutical Forms (Systemic)

• Oral: Solid forms (tablet, dragee, capsule, film-coated tablet, enteric tablet, chewable tablet, packet, effervescent tablet, cachet, pill) and liquid forms (syrup, elixir, solution, suspension, drop)
• Parenteral: Solution or suspension for injection, emulsion (ampoule, vial, powder for reconstitution), implantation pellet
• Inhalation: Gas, vapor, aerosol, inhaler, nebulizer
• Transdermal: Patch (TTS), ointment
• Others: Nasal spray