Route of administration
In
pharmacology and
toxicology, a
route of administration is the path by which a
drug, fluid, poison or other substance is brought into contact with the body.
[In toxicology, "exposition" may often be a more appropriate term, however "administration" can be used for deliberate substance use.]Obviously, 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). However, using the body's transport mechanisms for this purpose can be far from 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.
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 other routes 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
*epicutaneous (application onto the skin), e.g. allergy testing, topical
local anesthesia*inhalational, e.g.
asthma medications
*
enema, e.g. contrast media for imaging of the bowel
*eye drops (onto the
conjunctiva), e.g.
antibiotics for conjuncitivitis
*ear drops - such as antibiotics and
corticosteroids for
otitis externa*intranasal, e.g.
decongestant nasal sprays
*vaginal, e.g. topical estrogens, antibacterials
Enteral
*by
mouth (orally), many drugs as
tablets, capsules, or drops
*by
gastric feeding tube,
duodenal feeding tube, or
gastrostomy, many drugs and
enteral nutrition*
rectally, various drugs in
suppository or
enema form
*
intravenous (into a
vein), e.g. many drugs,
total parenteral nutrition*intraarterial (into an
artery), e.g.
vasodilator drugs in the treatment of
vasospasm and
thrombolytic drugs for treatment of
embolism*
intramuscular (into a
muscle), e.g. many
vaccines, antibiotics, and long-term psychoactive agents.
*
intracardiac (into the heart), e.g.
adrenaline during
cardiopulmonary resuscitation (not commonly performed anymore)
*
subcutaneous (under the skin), e.g.
insulin*
intraosseous infusion (into the
bone marrow) is, in effect, an indirect intravenous access because the bone marrow drains directly into the venous system. This route is occasionally used for drugs and fluids in emergency medicine and paediatrics when intravenous access is difficult
*
intradermal, (into the skin itself) is used for
skin testing some
allergens, and also for
tattoos
*intraperitoneal, (into the
peritoneum) is predominantly used in veterinary medicine and animal testing for the administration of systemic drugs and fluids due to the ease of administration compared with other parenteral methods.
Parenteral (other than oral)
*
transdermal (diffusion through the intact skin), e.g. transdermal opioid patches in pain therapy
*transmucosal (diffusion through a mucous membrane), e.g.
cocaine snorting, sublingual
nitroglycerine*inhalational, e.g.
inhalational anestheticsOther
*intraperitoneal (infusion or injection into the
peritoneal cavity), e.g.
peritoneal dialysis*epidural (synonym: peridural) (injection or infusion into the
epidural space), e.g. epidural anesthesia
*intrathecal (injection or infusion into the
cerebrospinal fluid), e.g. antibiotics,
spinal anesthesia*
intravitrealSome 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, 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 few drug preparations 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.
*
Pharmaceutical form*
Medical injection*
Catheter*
Intravenous therapy*
Hypodermic needle*
FDA Center for Drug Evaluation and Research Data Standards Manual: Route of Administration.*
FDA Center for Drug Evaluation and Research Data Standards Manual: Dosage Form.
