Lecture 6 Flashcards
What is the route of administration of a drug primarily determined by?
- Properties of the drug – water or lipid solubility, ionisation, etc.
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Therapeutic objectives – desire for rapid onset of action, need for long term administration, restriction to a local site, etc.
- “What are you trying to achieve and how can you best achieve it?”
What are some commonly used routes of drug administration?
- Pareneteral: IV, IM, SC
- Sublingual
- Inhalation
- Oral
- Transdermal patch
- Rectal
- Topical
What are the 2 major routes of drug administration?
- ENTERAL - goes through a hole/orifice
- PARENTERAL - inject = break the skin barrier
List some Enteral, Parenteral and other routes of drug administration
Enteral
- Oral; Sublingual; Rectal
Parenteral
- Intravascular (IV) Intramuscular (IM) Subcutaneous (SC)
Other
- Inhalation; Intranasal; Intrathecal / intraventricular; Topical; Transdermal
Describe The oral route of drug administration
- mc
- most variable(effects)
- most complicated pathway(long) to the tissues
- easiest for compliance with conscious Pt
- usually absorbed by the upper GI tract (not stomach) then passes through the portal venous system where it can undergo First-Pass Metabolism
Why would you need to consider other routes of administration instead of Oral?
- If The drug is unstable or is rapidly inactivated in the GI tract.
- Loss of drug absorbance via the GI tract
- limited amounts of the drug gets through first-pass metabolism in the liver so an insufficient levels reach the target, vomiting or a disease state.
- Therapeutic effects demand local administration as systemic absorption would lead to adverse drug effects
Describe FIRST-PASS METABOLISM
- drug is absorbed in upper GI (oral)
- enters venus sytem must go through hepatic prortal vein to liver where it metabolises and degrades
- then exits via bile duct and returns to the venus system
- If drug is administered via IV drip it directly enters venous system and bipasses the liver (1st pass metabolism)
Describe the SUPLINGUAL route of administration
placement under tongue allows for drug to diffuse into the capillary network, avoiding first-pass liver metabolism and directly entering the systemic circulation.
Describe the RECTAL route of administation
- Since there is limited portal blood flow (very few BV go to the liver), exposure of drug to first-pass metabolism is less than with the oral route.
- useful if drug induces vomiting when given orally or if patient is already vomiting
What are some reasons for administering a drug via the PARENTERAL route?
- for drugs that are poorly absorbed from the GI tract
- for drugs that are unstable in the GI tract
- in treatment of unconscious patients
- in treatment where rapid onset of action is required
- Provides most control over actual dose delivered - (can assume almost 100% gets to target organ)
Describe INTRAMUSCULAR & SUBCUTANEOUS routes of administration
both require absorption of drug into tissue. Use of carrier vehicles (such as peanut oil) allows for control of delivery
intramuscular = drug injected directly into skeletal muscle
subcutaneous = absorbtion of drugs from subcutaneous tissues
Describe the INHALATION route of administration
allows for rapid delivery of drug across a large surface area (pulmonary/respiratory system). Used for drugs that are gases or aerosols.
Describe the INTRATHECAL/INTRAVENTRICULAR routes of administration
Introduction of drugs directly into cerebral spinal fluid.
Describe a TOPICAL route of administration
Used when a local effect of the drug is required.
For Example:
- eye drops
- ear drops
- intranasal
- via skin
Describe a TRANSDERMAL route of administration
This administration route achieves systemic effect by application of drugs to skin via a transdermal patch. Although absorption through skin may vary this route is used when sustained delivery is needed.
