Routes of Drug Administration

Routes of Drug Administration
The route of administration (ROA) that is chosen may have profound effect upon the speed and efficiency with which the drug acts.

Definition 
A route of administration is the path by which a drug, fluid, poision or other substance is brought into contact with the body



Drugs are introduced into the body by several routes. They may be 
  • Taken by mouth (orally) 
  • Injection routes given by injection into vein ( intravenously, iv ) into the muscle ( intramuscular, IM ) into space around the spinal cord (intrathecally), or beneath the skin (subcutaneously,SC)
  • Place under the tongue (sublingually) or between gums and check(buccally)
  • Inserted in rectum (rectally) or vagina(vaginally)
  • Place in eye(ocular route) or ear (by the otic route)
  • Nasally sprayed into nose and absorbed through nasal membranes 
  • Breathed into the lungs, usually through the mouth ( by inhalation) or mouth and nose ( by nebulization)
  • Applied to the skin (cutaneously) for a local (topically) or bodywide (systemic) effect 
  • Delivered through the skin by a patch (transdermally) for systemic effect 
Each route has specific purpose, advantages, and disadvantages.

Oral route 
Advantages
  • Convenient can be self administered,pain-free, easy to take 
  • Absorption takes place the whole length of GI track 
  • Cheap compared to most other parenteral routes
Disadvantages
  • Sometimes inefficient only part of the drug may be absorbed
  • First pass effect drug absorbed orally are initially transported to liver via the portal vein 
  • Irritation to gastric mucosa nausea and vomiting
Parenteral route 
Advantages
  • Precise, accurate and immediate onset of action, 100% bioavailability.
  • Suitable for injection of drug in aqueous solution ( rapid action ) and drug in suspension or emulsion ( sustained release ) 
  • When a person cannot take anything by mouth
Disadvantage
  • Pain at injection site for certain drugs 
  • Risk of embolism 
  • High concentration attained rapidly leading to greater risk of adverse effects
Buccal/Sublingual route 
Advantages
  • Avoid hepatic first pass 
  • Rapid absorption
  • Drug stability 
Disadvantages
  • Holding the dose in the mouth is inconvenient
  • Small doses only can be accommodated easily
  • Unpleasant taste of some drugs 
Rectal route 
Advantages
  • Avoid hepatic first pass 
  • Patient unable to take drug orally 
Disadvantages
  • Erratic absorption
  • Not well accepted 
Inhalation route 
Advantages
  • Large surface area 
  • Thin membrane seprate alveoli from circulation
  • High blood flow as result a rapid onset of action 
Disadvantages
  • Most addictive route of administration because it hits the brain quickly 
  • Difficulties in regulating the exact amount of dosage 
  • Sometimes patient having difficulties in giving themselves a drug by inhaler 
The Route of Administration is determined by the physical characteristics of drug, the speed which the drug is absorbed and or released, as well as the need to bypass hepatic metabolism and achieve high concentration at particular sites 

No single method of drug administration is ideal for all drugs in all circumstances

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