Rectal administration (colloquially known asboofing orplugging) uses therectum as aroute of administration formedication and other fluids, which areabsorbed by the rectum'sblood vessels,[Note 1] and flow into the body'scirculatory system, which distributes the drug to the body'sorgans andbodily systems.[Note 2]
In addition to pharmacological effects, rectal administration has some properties which can be advantageous for the use in medicine. Rectal administration can allow patients to remain in the home setting when the oral route is compromised. Unlikeintravenous lines, which usually need to be placed in aninpatient environment and require special formulation ofsterile medications,[1] a specialized rectalcatheter can be placed by a clinician, such as ahospice nurse or home health nurse, in the home. Many oral forms of medications can be crushed and suspended in water to be given via a rectalcatheter.
The rectal route of administration is useful for patients with any digestive tract motility problem, such asdysphagia,ileus, orbowel obstruction, that would interfere with the progression of the medication through the tract. This often includes patientsnear the end of life (an estimated 1.65 million people are inhospice care in the US each year).[2] Because using the rectal route enables a rapid, safe, and lower cost alternative to administration of medications,[3] it may also facilitate the care of patients inlong-term care orpalliative care, or as an alternative tointravenous orsubcutaneous medication delivery in other instances.
Besides its application in medicine, rectal administration is also employed by users ofpsychoactive substances. As in the medical procedure, the psychoactive drug is injected via the anus and is absorbed by the rectum'sblood vessels.
A study shows that awareness of rectal administration as a possible route of administration varies greatly among users of different drugs. The knowledge of rectal administration is highest among groups of users ofalcohol,stimulants andopioids, where over 30% of users are aware of it.[4]
The reasons for rectal administration are largely the same as with medicinal drugs: Bypassing the first-pass effect, fast onset, and a relatively high bioavailability with some drugs.[5]
Rectal administration is sometimes thought of as a safer alternative tointravenous injection of psychoactive substances,[6] which carries a significant risk of infections and illnesses likepulmonary granulomatosis.[7]
However, rectal administration of psychoactive drugs has risks associated with it also.[4] The combination of a brief acting time (compared to oral administration) and an unpredictable absorption-rate can, particularly for new users, result in a risk ofoverdoses. Use of shared ornon-sterile equipment can increase the risk of acquiringsexually transmitted infections.[8] Some psychoactive substances likesubstituted amphetamines can induce a strongvasoconstriction in the rectal vasculature and lead tointestinal ischemia.[4]
As with illicit psychoactive drugs in general, risks connected to rectal administration stem from the often unknown purity and composition of the drugs. This leads to the user not knowing if and what substances,by-products orcutting agents are present in their drugs[9] before administering them rectally. Possible impurities or falsely marketed substances greatly increase the risk of administering illicit drugs rectally.
A drug that is administered rectally will in general (depending on the drug) have a faster onset, higherbioavailability, shorter peak, and shorter duration thanoral administration.[10][11] Another advantage of administering a drug rectally, is that it tends to produce lessnausea compared to the oral route and prevents any amount of the drug from being lost due toemesis (vomiting). In addition, the rectal route bypasses around two-thirds of thefirst-pass metabolism as the rectum's venous drainage is two-thirdssystemic (middle andinferior rectal vein) and one-thirdhepatic portal system (superior rectal vein). This means the drug will reach the circulatory system with significantly less alteration and in greater concentrations.[Note 3]
Rectal administration of medication may be performed with any of the following:
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