Rectal (medicine)
Encyclopedia
The rectal
route of administration
(ROA) is a way of administering drugs into the rectum to be absorbed
by the rectum's blood vesselsThe rectum
has numerous amounts of blood vessels available to absorbed the drug introduced into the rectum. and into the body's circulatory system
which distributes the drug to the body's organs and various systemsThe organs and systems include the (depending on if the drug is able to pass the blood-brain barrier
(BBB) or not) central nervous system
(CNS), brain
, peripheral nervous system
(PNS), cardiovascular system (CVS), et cetera
. where the drug elicits its effects.
A drug that is administered rectally will in general (depending on the drug) have a faster onset, higher bioavailability
, shorter peak, and shorter duration than the oral
route.
Another advantage of administering a drug rectally is that it tends to produce less nausea
compared to the oral route and also prevents any amount of the drug from being lost due to emesis (vomiting, "throwing up", or "puking") since the drug is in the rectum, not the stomach, and the contents of the rectum are not lost when there is emesis.
In addition the rectal route bypasses
first-pass metabolism, meaning the drug will reach the circulatory system with significantly less alteration and in greater concentrationsOther ROAs that bypass first-pass metabolism include inhalation
(smoking
, vaporizing, etc.), intravenous injection (IV), insufflation
("snorting"), et cetera, but the oral
route does not bypass first-pass metabolism..
The rectal ROA may be performed with either of the following:
Rectum
The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...
route of administration
Route of administration
A route of administration in pharmacology and toxicology is the path by which a drug, fluid, poison, or other substance is taken into the body.-Classification:Routes of administration are usually classified by application location...
(ROA) is a way of administering drugs into the rectum to be absorbed
Absorption (Pharmacokinetics)
In pharmacology , absorption is the movement of a drug into the bloodstream.Absorption involves several phases...
by the rectum's blood vesselsThe rectum
Rectum
The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...
has numerous amounts of blood vessels available to absorbed the drug introduced into the rectum. and into the body's circulatory system
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...
which distributes the drug to the body's organs and various systemsThe organs and systems include the (depending on if the drug is able to pass the blood-brain barrier
Blood-brain barrier
The blood–brain barrier is a separation of circulating blood and the brain extracellular fluid in the central nervous system . It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion...
(BBB) or not) central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
(CNS), brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
, peripheral nervous system
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...
(PNS), cardiovascular system (CVS), et cetera
Et cetera
Et cetera is a Latin expression that means "and other things", or "and so forth". It is taken directly from the Latin expression which literally means "and the rest " and is a loan-translation of the Greek "καὶ τὰ ἕτερα"...
. where the drug elicits its effects.
A drug that is administered rectally will in general (depending on the drug) have a faster onset, higher bioavailability
Bioavailability
In pharmacology, bioavailability is a subcategory of absorption and is used to describe the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. By definition, when a medication is administered...
, shorter peak, and shorter duration than the oral
Oral administration
Oral administration is a route of administration where a substance is taken through the mouth.-Terminology:Per os is an adverbial phrase meaning literally from Latin "by mouth" or "by way of the mouth." The expression is used in medicine to describe a treatment that is taken orally. The...
route.
Another advantage of administering a drug rectally is that it tends to produce less nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
compared to the oral route and also prevents any amount of the drug from being lost due to emesis (vomiting, "throwing up", or "puking") since the drug is in the rectum, not the stomach, and the contents of the rectum are not lost when there is emesis.
In addition the rectal route bypasses
Coronary artery bypass surgery
Coronary artery bypass surgery, also coronary artery bypass graft surgery, and colloquially heart bypass or bypass surgery is a surgical procedure performed to relieve angina and reduce the risk of death from coronary artery disease...
first-pass metabolism, meaning the drug will reach the circulatory system with significantly less alteration and in greater concentrationsOther ROAs that bypass first-pass metabolism include inhalation
Inhalation
Inhalation is the movement of air from the external environment, through the air ways, and into the alveoli....
(smoking
Smoking
Smoking is a practice in which a substance, most commonly tobacco or cannabis, is burned and the smoke is tasted or inhaled. This is primarily practised as a route of administration for recreational drug use, as combustion releases the active substances in drugs such as nicotine and makes them...
, vaporizing, etc.), intravenous injection (IV), insufflation
Insufflation (medicine)
Insufflation is the practice of inhaling a substance. Insufflation has limited medical use, but is a common route of administration with many respiratory drugs used to treat conditions in the lungs and paranasal sinus .The technique is common for many recreational drugs and is also used for some...
("snorting"), et cetera, but the oral
Oral administration
Oral administration is a route of administration where a substance is taken through the mouth.-Terminology:Per os is an adverbial phrase meaning literally from Latin "by mouth" or "by way of the mouth." The expression is used in medicine to describe a treatment that is taken orally. The...
route does not bypass first-pass metabolism..
Methods
- A suppositorySuppositoryA suppository is a drug delivery system that is inserted into the rectum , vagina or urethra , where it dissolves.They are used to deliver both systemically-acting and locally-acting medications....
, a drugDrugA drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
delivery system inserted into the rectum. - An enemaEnemaAn enema is the procedure of introducing liquids into the rectum and colon via the anus. The increasing volume of the liquid causes rapid expansion of the lower intestinal tract, often resulting in very uncomfortable bloating, cramping, powerful peristalsis, a feeling of extreme urgency and...
, the act of introducing a liquidLiquidLiquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
-drug solutionSolutionIn chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
(drug(s) dissolved in water, the amount usually being less than 10 millilitres) into the rectum and sometimes the colon (usually when more liquid is used).