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A route of administration in pharmacology and toxicology is the path by which a drug, fluid, poison, or other substance is brought into contact with the body.[1]

A substance must be transported from the site of entry to the part of the body where its action is desired to take place (even if this only means penetration through the stratum corneum into the skin). Using the body's transport mechanisms for this purpose, however, is not trivial. The pharmacokinetic properties of a drug (that is, those related to processes of uptake, distribution, and elimination) are critically influenced by the route of administration.

Contents

Classification

Routes of administration can broadly be divided into:

  • topical: local effect, substance is applied directly where its action is desired.
  • enteral: desired effect is systemic (non-local), substance is given via the digestive tract.
  • parenteral: desired effect is systemic, substance is given by routes other than the digestive tract.

The U.S. Food and Drug Administration recognizes 111 distinct routes of administration. The following is a brief list of some routes of administration.

Topical

Enteral

Enteral is any form of administration that involves any part of the gastrointestinal tract:

Parenteral

Vaginal

Other

Advantages and Disadvantages

There are advantages and disadvantages to each route of administration

Inhalation

*Advantages*

  • Fastest method, 7–10 seconds for the drug to reach the brain
  • User can titrate (regulate the amount of drug they are receiving)

*Disadvantages*

  • Typically a more addictive route of administration because it is the fastest, leading to instant gratification. In addition, drugs taken by inhalation do not stay in the bloodstream for as long, causing the user to redose more quickly and intensifying the association between consuming the drug and its effects.
  • Difficulties in regulating the exact amount of dosage
  • Patient having difficulties administering a drug via inhaler

Injection

Injection incompasses intravenous (IV), intramuscular (IM), and subcutaneous (subcut) [7]

*Advantages*

  • Fast: 15–30 seconds for IV, 3–5 minutes for IM and subcutaneous subcu
  • 100% bioavailability
  • suitable for drugs not absorbed by the gut or those that are too irritant (anti-cancer)
  • One injection can be formulated to last days or even months, e.g., Depo-Provera, a birth control shot that works for three months
  • IV can deliver continuous medication, e.g., morphine for patients in continuous pain, or saline drip for people needing fluids

*Disadvantages

  • Onset of action is quick, hence more risk of addiction when it comes to injecting drugs of abuse
  • Patients are not typically able to self-administer
  • Belonephobia, the fear of needles and injection.
  • If needles are shared, there is risk of HIV and other infectious diseases
  • It is the most dangerous route of administration because it bypasses most of the body's natural defenses, exposing the user to health problems such as hepatitis, abscesses, infections, and undissolved particles or additives/contaminants
  • If not done properly, potentially fatal air boluses (bubbles) can occur.
  • Need for strict asepsis

Uses

  • Some routes can be used for topical as well as systemic purposes, depending on the circumstances. For example, inhalation of asthma drugs is targeted at the airways (topical effect), whereas inhalation of volatile anesthetics is targeted at the brain (systemic effect).
  • On the other hand, identical drugs can produce different results depending on the route of administration. For example, some drugs are not significantly absorbed into the bloodstream from the gastrointestinal tract and their action after enteral administration is therefore different from that after parenteral administration. This can be illustrated by the action of naloxone (Narcan), an antagonist of opiates such as morphine. Naloxone counteracts opiate action in the central nervous system when given intravenously and is therefore used in the treatment of opiate overdose. The same drug, when swallowed, acts exclusively on the bowels; it is here used to treat constipation under opiate pain therapy and does not affect the pain-reducing effect of the opiate.
  • Enteral routes are generally the most convenient for the patient, as no punctures or sterile procedures are necessary. Enteral medications are therefore often preferred in the treatment of chronic disease. However, some drugs can not be used enterally because their absorption in the digestive tract is low or unpredictable. Transdermal administration is a comfortable alternative; there are, however, only a few drug preparations are suitable for transdermal administration.
  • In acute situations, in emergency medicine and intensive care medicine, drugs are most often given intravenously. This is the most reliable route, as in acutely ill patients the absorption of substances from the tissues and from the digestive tract can often be unpredictable due to altered blood flow or bowel motility.

Notes

  1. ^ "Exposition" may be a more appropriate term in toxicology. "Administration", however, can be used for deliberate substance use.
  2. ^ Fenway Community Health
  3. ^ MDMA (ecstasy) metabolites and neurotoxicity: No occurrence of MDMA neurotoxicity from metabolites when injected directly into brain, study shows.
  4. ^ A potential application for the intracerebral injection of drugs entrapped within liposomes in the treatment of human cerebral gliomas.
  5. ^ Blood-brain barrier changes following intracerebral injection of human recombinant tumor necrosis factor-α in the rat
  6. ^ Acute Decreases in Cerebrospinal Fluid Glutathione Levels after Intracerebroventricular Morphine for Cancer Pain
  7. ^ http://www.ismp.org/Tools/errorproneabbreviations.pdf

See also

References

Inaba, Darryl and Cohen, William. 2007. Uppers, Downers, All Arounders. Medford, Oregon: CNS Productions, Inc.

External links








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