Why is the enteral route seem by far the most common way to administer a drug to the body?

  • 1
    $\begingroup$ Who says it is the safest route? $\endgroup$
    – Chris
    Aug 30, 2014 at 20:57
  • $\begingroup$ Question seems valid to me. It appears difficult to deny that the oral route is the most common administration route. However, it is true that any answer given to this question will be partly opinion-based... $\endgroup$
    – Raoul
    Sep 8, 2014 at 17:27

2 Answers 2


Let's review drug administration routes, and see for yourself:

  • transdermal/ionophoric: expensive, unreliable release concentrations (which makes it expensive because of the extensive research needed for controlled release), noticeable to others ("why do you have that skin patch, mom?" Er...)
  • Sublingual: quite similar to oral route, however absence of first pass hepatic metabolism can result in completely different blood concentrations between the two routes. Impairs speech. Could cause mouth irritation (quite disabling). Requires patient compliance.
  • intravenous: quite unpractical in outpatient settings. Invasive measure.
  • intramuscular/intradermal: hurts. As all things using a needle. Usable, but impractical in the outpatient setting. Can lead to skin lesions (insulin injection in diabetes, for example)
  • rectal: culturally unacceptable to some, unreliable release.
  • vaginal: similar to rectal, but only for women obviously
  • spinal/epidural: very invasive, only in inpatient settings.
  • topical: usually only acts locally, can cause discomfort (eyes)
  • oral/enteral: well known pharmacokinetics, mostly invisible to others, practical in the outpatient setting, requires limited patient compliance, well known excipients. Of course there can be secondary effects, but that is the case for all administration routes. Most common side effects are abdominal discomfort and nausea, but no one can see you in the water closet. Plus people are used to see pills as medication, something which might not be the case for other routes, depending on the cultural background of the patient.

This answer is of course somewhat subjective, however the importance of the patient's perception and his/her view of what the administration route implies socially cannot be overemphasized.

  • 1
    $\begingroup$ Also IM (Intramuscular). $\endgroup$
    – L.B.
    Sep 2, 2014 at 18:33
  • $\begingroup$ i've done the sublingual with powerful medications and its not really that bad as long as your mouth doesn't blister and your oral nerves are not so affected. the taste can be abominable though. $\endgroup$
    – user1357
    Sep 2, 2014 at 22:00

Pill, tablet and time release are great enteral treatments because of their ability to control dosage by the patient at home. Compared with an IV and oil/sublinguals they are less effective at due to the greater risk of causing toxic damage to the liver and kidneys but there is little chance of overdose by reason of mechanical failure. That is the reason that viagra and metformin are first lines of defense; followed by insulin and alprostadil if they so fail. You do not infect yourself typically with a pill but with an injection its possible for a needle to be dirty. Likewise also there is the ever fear of an air bubble.

  • $\begingroup$ I would say that tablets are actually one of the hardest methods to regulate dosage over time. The drug release rate can be modified by the pH of the gut, how much food the patient has eaten, and other factors. The drugs hit the liver first, and experience first pass metabolism, usually losing most of the drug in the process. Metabolites can be excreted in the bile and reabsorbed in the intestines. While the IV route requires a needle, it guarantees the exact dose gets into the blood, and allows more of the drug to avoid the liver and hit the target site. $\endgroup$
    – user137
    Aug 31, 2014 at 4:34
  • $\begingroup$ @user137 is that better? $\endgroup$
    – user1357
    Aug 31, 2014 at 4:35
  • 1
    $\begingroup$ I would say that the reason sildenafil is typically preferred over alprostadil is largely due to Viagra being a nice friendly tablet and alprostadil being a particularly daunting injection into a sensitive area for patients. Perhaps this goes some way to indicating one of the main reasons many drugs are enteral in administration - patients find it easier. $\endgroup$
    – Rory M
    Aug 31, 2014 at 22:31
  • $\begingroup$ I think the edited answer does suggest that pills are preferred because they are easier to take, and the patient can do it by themselves. Patients can do their own injections, but must be trained and compliance is harder. However, pills are not foolproof. Taking too many pills is a common method of suicide, which is why the UK switched to putting acetaminophen in blister packs. And people who like to cut pills in half to swallow them easier inadvertently defeat the extended release mechanism, and cause drug levels to spike too fast. $\endgroup$
    – user137
    Sep 1, 2014 at 15:20
  • $\begingroup$ @RoryM yes agreed $\endgroup$
    – user1357
    Sep 1, 2014 at 23:22

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