routes of administration

week 1 ppt

clinical pharmacology

• science of drugs and their use in humans

what is a drug?

• molecule which has a physiological effect when ingested or otherwise introduced into the body

bioavailibility

• the proportion of administered drug which reaches systemic circulation unchanged and is thus available for distribution to site of action

intravenous injection

• achieves 100% bioavailibilty

• all of drug dose reaches systemic circulation unchanged

• rapid and powerful action

• incovenient for long term therapy

subcutaneous injection

• consistent absorption from small volumes 

• uptake into bloodstream via absorption across capillary walls

intramuscular injection

• access to large blood flow in muscles of upper arm

• route is reliable and can be suitable for certain irritant drugs

• good for depot preparations (longer lasting drug release)

• rapid absorption and good for larger volumes compared with SC injections (common for vaccinations)OR

oral routes

• very common, safe, convenient

• always less than 100% bioavailability achieved

• exposure to pH, enzymes and microbial activity in gut

• exposure to first pass metabolism

• absorption can depend on rates of GI transit

• requires patient compliance

mucosal routes

• routes:

1. sublingual, buccal

2. nasal

3. vaginal, rectal

• achieves rapid transit to systemic circulation

• avoids first pass metabolism

• drug stability (pH in mouth is neutral compared to acidic in stomach)

inhalation route

• aerosols: for airway disease

• lipid soluble anaesthetics: rapid absorption

• avoids first pass metabolism

transdermal route

• outer skin layer in fluences rate of absorption

• low input rates can aid long term use

topical route

• especially for dermatology

• e.g- steroid cremas for skin conditions

pharmacokinetics

• what the body does to the drug

• study of drug movements within the body

pharmacodynamics

• what drug does to the body

• study of drug effects and mechanisms of action

ADME criteria

Absorption

Distribution

Metabolism

Excretion