Drug Application Types and Routes

Application Places of Drugs

• Drugs need to be present at a certain concentration to have an effect.
• The needed concentration is called MEK (minimum effective concentration).
• The active substance has to reach the place of effect in MEK when drugs are administered.
• Determining the amounts and application sites facilitates this

Routes of Drug Application

• Routes of application are categorised into two: local and systemic.
• The classification depends on the purpose of the drug and the condition/location to be treated.
• The choice of administration route depends on drug and patient factors.

Local Application Ways

• Drug is intended to affect the body surface.
• Examples of local application routes include:
  • 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
• Used for drugs that have minimal or no absorption from these areas
• There are no or minimal systemic side effects or toxicity

Intracutaneous Application

• 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 Application

• Used in various infections
• Ophthalmic preparations must be sterile; these are called 'colir'

Intranasal Application

• Used in diseases of the nasal mucosa and paranasal sinuses
• Anti-inflammatory, vasoconstrictor, local anesthetic drug solutions can be applied this way
• Systemic application is also 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 administered to create a local effect
• Target the meninges or spinal nerve roots

Intracardiac Application

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

Intraperitoneal Application

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

Intraarticular Application

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

Rectal and Colonic Application

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

Intrauterine Application

• Oxytocic hormone is injected into the myometrium to accelerate uterine contraction after cesarean sections
• This is done to reduce bleeding

Intravaginal Application

• 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 Application

• Administration of drugs that are not absorbed from the gastrointestinal tract, or are broken down there
• Injected into a vein or tissue with a sterile syringe and starts to work quickly

Transdermal Application

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

Inhalation

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

Oral (Per Os) Application

• Most commonly used, practical, and economical route
• Drugs must pass through the liver after absorption before entering systemic circulation.
• Some may be inactivated, and absorption may also be incomplete

Sublingual Application

• Used when a drug effect is desired to start very quickly
• Quickly dissolving, able to create an effect with small amounts, and highly soluble in fat
• Drugs prescribed are given in the form of small tablets (nitroglycerin, nifedipine)

Rectal Administration

• Applying drugs to the rectum, either a local or systemic effect is achieved by absorption from the rectal mucosa
• Drugs can be administered in the form of suppositories, enemas, or enemas
• More commonly used in patients who cannot take oral medication and in infants

Parenteral Administration

• Used for drugs that cannot be absorbed or broken down enough from the gastrointestinal tract when administered orally
• Effective for drugs that require rapid onset of effect, used in emergency situations
• Used when the patient is unconscious, unable to swallow, or experiencing nausea, vomiting, diarrhea, etc.

Parenteral Disadvantages

• Can be painful and 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) Application

• Only drugs that are water-soluble or water-mixable can be administered
• Application is preferred when a rapid effect is needed
• Application is also preferred 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 is the slow administration of large volumes of drug solutions (over 1-2 hours) into a vein

Intravenous Disadvantages

• Only water-soluble drugs can be administered
• Oily solutions and suspensions cannot be administered intravenously due to embolism
• Drugs with low water solubility may precipitate in the vein if injected rapidly
• Administered drug cannot be retrieved
• High risk of anaphylaxis
• Irritant drugs may cause tissue damage if extravasation occurs

Intramuscular (IM) Application

• 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 is mostly affected by blood flow in that area
• Massage or exercise increases absorption

Subcutaneous Application

• 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)
• The drug is then released slowly and regularly to provide patients with a long-lasting effect

Intraosseous Injection

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

Transdermal Drug Application

• The drug is applied to the skin surface for a systemic effect
• For highly lipophilic and small dose effective drugs like nitroglycerin, scopolamine, clonidine, fentanyl, and testosterone
• Can use a transdermal therapeutic system (patch, patch)

Inhalation Application Advantages

• The alveoli have a large surface area

• There is a highly permeable membrane

• The blood flow rate in the lungs is very high

• When inhaled, drugs quickly pass through the alveolar membrane in the lungs and enter the bloodstream

• Used for drugs that are gaseous and vaporous (sevoflurane)

• Also useful for drugs that have high fat solubility, such as general anesthetics (nitrous oxide), and asthma and COPD drugs

Application Areas of Local Drugs

• Epidermal: Ointment, pomade, cream, lotion, powder, soap, solution, liniment, plaster, or paste
• Intranasal: Nasal drops and nasal spray
• Intravaginal: Vaginal suppository, vaginal tablet, ointment, gel, or foam
• Buccal: Lozenge, solution, or gargle
• Rectal: Ointment, suppository, or enema
• Colon: enema
• External Ear Canal: Otic drops (solution, suspension)

Application Sites of Systemic Drugs

• Oral: tablet, dragee, capsule, film-coated tablet, enteric tablet, chewable tablet, packet, effervescent tablet, or cachet and pill
• Syrup, elixir, solution, suspension, drop (concentrated solution), lotion, or emulsion and extract
• Parenteral: Solution or suspension for injection, emulsion (ampoule, vial, or powder for reconstitution) can be used
• Inhalation: Gas, vapor, aerosol, inhaler, or nebulizer
• Transdermal: Patch (TTS) or ointment
• Other: Nasal spray