Route of administration Totally Explained

Everything about Route Of Administration totally explained

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.
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.

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 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), for example allergy testing, typical local anesthesia

inhalational, for example asthma medications

enema, for example contrast media for imaging of the bowel

eye drops (onto the conjunctiva), for example antibiotics for conjunctivitis

ear drops - such as antibiotics and corticosteroids for otitis externa

intranasal route (into the nose), for example decongestant nasal sprays

vaginal, for example topical estrogens, antibacterials

Enteral

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

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

Parenteral by injection or infusion

intravenous (into a vein), for example many drugs, total parenteral nutrition

intraarterial (into an artery), for example vasodilator drugs in the treatment of vasospasm and thrombolytic drugs for treatment of embolism

intramuscular (into a muscle), for example many vaccines, antibiotics, and long-term psychoactive agents

intracardiac (into the heart), for example adrenaline during cardiopulmonary resuscitation (no longer commonly performed)

subcutaneous (under the skin), for example 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

intrathecal (into the spinal canal) is most commonly used for spinal anesthesia and chemotherapy

intraperitoneal, (infusion or injection into the peritoneum) for example peritoneal dialysis

Other parenteral

transdermal (diffusion through the intact skin), for example transdermal opioid patches in pain therapy, nicotine patches for treatment of addiction

transmucosal (diffusion through a mucous membrane), for example insufflation (snorting) of cocaine, sublingual nitroglycerine, buccal (absorbed through cheek near gumline), vaginal suppositories

inhalational, for example inhalational anesthetics

Other

epidural (synonym: peridural) (injection or infusion into the epidural space), for example epidural anesthesia

intravitreal

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're receiving) Disadvantages

Most addictive route of administration because it hits the brain so quickly

Difficulties in regulating the exact amount of dosage

Patient having difficulties in giving themselves a drug by inhaler

Injection

Injection incompasses intravenous (IV), intramuscular (IM), and subcutaneous (subcu) Advantages

Fast: 15-30 seconds for IV, 3-5 minutes for IM and subcutaneous

One injection can be formulated to last days or even months, ex. Depo-Provera is a birth control shot that works for three months

IV can deliver continuous medication, ex. Morphine for patients in continuous pain, or saline drip for people needing fluids Disadvantages

Because it's fast, there's more risk of addiction when it comes to injecting drugs of abuse

If needles are shared, there's 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

If not done properly, air boluses (bubbles) can occur and can be fatal

Need of 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's here used to treat constipation under opiate pain therapy and doesn't 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 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.

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