Drug Application Routes and Places

Application Places of Drugs

• Drugs need to be present at a certain concentration to have an effect
• The concentration neededis called MEK (minimum effective concentration)
• Amounts and the application sites of drugs need to be determined, so an active substance reaches the place of effect in MEK

Drug Application Routes

• Routes of drug application are divided into 2
• Routes are based on the targeted purpose of the drug and the condition of the place where the drug is intended to affect
• Choice of administration route depends on drug and patient factors

Local Application Routes

• Epidermal
• Intracutaneous
• Intrathecal
• Intrapleural
• Intraperitoneal
• Intracardiac
• Intraarticular
• Intrauterine
• Intravaginal
• Into the rectum and colon
• On the conjunctiva
• Intranasal and buccal
• The place the drug is intended to affect needs to be on the body surface

Epidermal Application

• Only used for localized lesions in accessible areas
• Suited for drugs that have minimal or no absorption from these areas
• There should be 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

Conjunctiva Application

• Used in various infections
• Ophthalmic preparations called 'colir' are applied to the eye
• Must be sterile

Intranasal Application

• Used in diseases of the nasal mucosa and paranasal sinuses
• Anti-inflammatory, vasoconstrictor, and local anesthetic drug solutions are applied
• Systemic application is also possible

Buccal (Intraoral) Application

• Used for mouth and gum infections

External Ear Canal Application

• Medication applied in some diseases of the external ear canal or eardrum

Intrathecal Application

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

Intracardiac Application

• Used In emergency situations/ for cardiac resuscitation during cardiac surgery
• Stimulant drugs, like adrenaline, can be administered directly to the heart

Intraperitoneal Application

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

Intraarticular Application

• Corticosteroids/antibacterial drugs injected in some joint diseases

Rectal and Colonic Application

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

Intrauterine Application

• Oxytocic hormone is injected into the myometrium
• Used to accelerate uterine contraction following caesarean sections, reducing bleeding

Intravaginal application

• Medications often administered as pessary into the vagina
• Spermicide drugs in foam/gel form used to prevent pregnancy

Systemic Drug Application Methods

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

Enteral Administration

• Drugs not absorbed from the gastrointestinal tract or broken down are administered into a vein or tissue with a sterile syringe
• Starts working quickly

Transdermal application

• Drug applied to the skin in a special pharmaceutical form
• Formulation facilitates absorption from the skin and entry into the circulation

Inhalation

• Lipophilic drugs pass through the alveolar membrane in gas or vapor form
• Drug enters the general blood circulation

Oral Administration

• The most common, practical, & economical route.
• Drugs used orally must pass through the liver
• Drugs pass through the liver after absorption before entering systemic circulation, some are inactivated and absorption may be incomplete

Sublingual Administration

• Used when the drug effects needed quickly
• Able to create an effect with small amounts
• Quickly dissolving and highly soluble in fat
• Drugs in small tablets (nitroglycerin/nifedipine) are administered

Rectal Administration

• Applying drugs to the rectum to achieve a local or systemic effect through absorption from the rectal mucosa
• Drugs administered as suppositories or enemas
• Often used for those who cannot take oral medication/infants

Parenteral Administration

• Used when drugs cannot be absorbed, or broken down in sufficient amounts from the gastrointestinal tract
• Used when a rapid onset of effect is needed in emergency situations
• Used when a patient is unconscious, unable to swallow, or experiencing nausea/vomiting/ diarrhea

Disadvantages of Parenteral Adminstration

• It is painful
• Causes vascular or tissue damage
• Creates psychological stress
• Patient cannot administer it alone
• Disadvantages include the expense of a specialised pharmaceutical form used

Intravenous Aministration

• Only water-soluble/water-mixable drugs can be administered this way
• Preferred when a rapid effect is desired/if patient is unconscious/cannot swallow
• Bioavailability is usually 100%
• Drug solutions up to 10 ml are injected in 1-2 minutes
• Intravenous infusion: slow administration of large volumes of drug solutions (over 1-2 hours) into a vein

Disadvantages of Intravenous Administration

• Only water-soluble drugs can be administered
• Oily solutions and suspensions cannot be administered this way
• Injected drugs with a low water solubility precipitate in the vein if injected rapidly (diazepam, 5 mg/min)
• Administered drugs cannot be retrieved
• High risk of anaphylaxis
• Irritant drugs may cause tissue damage if extravasation occurs

Intramuscular Administration

• Injecting the drug into the appropriate muscle tissue
• The gluteal/deltoid muscle is usually preferred
• Solution should not exceed 5 ml
• Absorption of the injected drug is affected by blood flow
• Massage or exercise increases absorption

Subcutaneous Administration

• The outer surface of humerus/femur region preferred
• Max 2 ml of solution to prevent pain on the skin
• Irritant drugs should be applied intramuscularly
• Some drugs are placed under the skin as implants or pellets (compressed tablets),,drug is released slowly, & regularly, = providing long-lasting effect

Intraosseous injection

• In infants/sometimes adults, the drug is injected if veins can cannot be found
• Drug is injected into a suitable bone marrow (sternum)
• Drug then passes rapidly into the blood, this is a very rare method

Transdermal Administration

• Applies the drug to the skin surface for systemic effect
• Highly lipophilic + small dose effective drugs ,such as nitroglycerin, scopolamine, clonidine, fentanyl, +testosterone are applied in this way
• Uses a transdermal therapeutic system (patch)

Inhalation application:

• Alveoli have a very large surface area and a highly permeable membrane
• Blood flow rate in the lungs is very high
• Inhaled, they quickly pass through the alveolar membrane + enter the bloodstream
• Gaseous and vaporous drugs (sevoflurane) /high fat solubility, like general anesthetics (nitrous oxide), or asthma/COPD drugs, are often administered this way

Application Areas of Drugs and Pharmaceutical Forms (Local)

• Epidermal drugs are administered as ointment, pomade, cream, lotion, powder, soap, solution, liniment, plaster, paste
• Intranasal drugs are administered as nasal drops or spray
• Intravaginal drugs are administered as vaginal suppository, vaginal tablet, ointment, gel, foam
• Buccal drugs are administered as lozenge, solution, gargle
• Rectal drugs are administered as ointment or suppository
• Colon drugs are administered as an enema
• Otic drugs are administered as (ear) drops (solution or suspension)

Application Sites of Drugs and Pharmaceutical Forms (Systemic)

• Oral drugs are administered as solid forms: tablet, dragee, capsule, film-coated tablet, enteric tablet, chewable tablet, packet, effervescent tablet, cachet, or pill
• Oral drugs are administered as liquid forms: syrup, elixir, solution, suspension, or drop (concentrated solution), lotion, or emulsion, or extract
• Parenteral drugs are administered as solution or suspension for injection, emulsion (ampoule, vial, powder for reconstitution), and implantation pellet
• Inhalation drugs as gas, vapor, aerosol, inhaler, or nebulizer
• Transdermal drugs a patch (TTS) or ointment
• Other drugs are administered as a nasal spray