Rectal administration

If a drug undergoes an extensive first-pass metabolism (e.g., morphine, metoclopramide, ergotamine, or lidocaine), rectal administration may produce an even higher plasma level. The prolonged rectal administration of multiple drugs may produce local irritation or even rectal ulceration. 

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Extravasation of barium sulfate iato the peritoneal cavity through a perforated GI tract can produce serious adverse reactions. When a perforation is suspected, the use of a water-soluble iodinated contrast medium is iadicated. In this case, oral or rectal administration of sodium or meglumine-sodium salts of diatrizoic acid (6) and oral use ofiohexol (11) are the preferred procedures. 

Oral administration of mesalamine may cause abdominal pain, nausea, headache dizziness, fever, and weakness. The adverse reactions associated witii rectal administration are less than those seen witii oral administration, but headache abdominal discomfort, flu-like syndrome, and weakness may still occur. Olsalazine administration may result in diarrhea, abdominal discomfort, and nausea Sulfasalazine is a sulfonamide witii adverse reactions the same as for the sulfonamide drugs (see Chap. 6). 

Rectal Administration. The administration of drugs by a solid rectal dosage form (i.e., suppositories) results in a wide variability in the rate and extent of absorption in children [79]. This fact, coupled with the inflexibility of a fixed dose, makes this a route that should not be promoted for pediatric patients. At least one death involving a 7-month-old infant can be directly attributed to the use of solid rectal dosage form of a therapeutic dose of morphine [80]. 

Rectal administration of a drug is considered unacceptable by adolescents and various ethnic groups. 

The ability of NB-355 to stimulate locomotor activity and induce dyskinesia in MPTP-treated squirrel monkeys was studied (MPTP induces parkinsonism) [9], NB-355 was similar to L-dopa in stimulating locomotor activity. Furthermore, NB-355 induced less severe dyskinesia than was seen with L-dopa. Some other prodrugs of L-dopa include short-chain alkyl esters (methyl, ethyl, isopropyl, butyl, hydroxypropyl, and hydroxybutyl) intended for rectal absorption [10], These esters of L-dopa have high water solubility (>600 mg/mL). Initial bioavailability studies indicated that all of these esters, with the exception of the hydroxypropyl ester, resulted in significantly greater bioavailability than that obtained with L-dopa itself. However, given the high level of esterase activity in the small intestine, the use of these compounds is limited to rectal administration. 

H Sandberg-Gretzen, M Ryde, G Jarnerot. Absorption and excretion of azodisal sodium and its metabolites in man after rectal administration of a single 2-g dose. Scan J Gastroenterol 18 571-575, 1983. 

A bowel movement may result within a few hours of oral doses and in 1 hour or less after rectal administration. 

Rectal administration is a reasonable alternative in patients in whom oral or parenteral administration is not feasible. 

Rectal Administration Rectal administration of a drug may be applied when the patient is unable to take the drug orally and some other routes are impractical. The drug administered via the rectum is absorbed and partially bypasses the liver. However, the absorption of drugs may be unreliable in certain cases. 

Indometacin, which is a non-steroidal anti-inflammatory drug, inhibits the enzyme cyclo-oxygenase implicated in inflammatory reactions. Indometacin is more effective as an anti-inflammatory agent than ibuprofen and tends to have a higher side-effect profile, including headache, diarrhoea and gastrointestinal disturbances. Rectal administration reduces but does not prevent gastrointestinal tract disturbances. 

Taking broken, chewed, or crushed tablets could lead to the rapid release and absorption of a potentially fatal dose of oxycodone. OxyContin is not indicated for rectal administration. Data from a study involving 21 normal volunteers show that OxyContin tablets administered per rectum resulted in an AUC 39% greater and a Cmax... 

Rectal administration Rectally administered barbiturates are absorbed from the colon and are used occasionally in infants for prolonged convulsive states, or when oral or parenteral administration may be undesirable. 

Rectal administration For outpatient treatment when oral dosing is not possible, suppositories containing 25 mg metoclopramide have been extemporaneously compounded (5 pulverized oral tablets in polyethylene glycol). Administer 1 suppository 30 to 60 minutes before each meal and at bedtime. 

Sznitowska M. et al.. Bioavailability of diazepam from aqueous-organic solution, submicron emulsion and solid lipid nanoparticles after rectal administration in rabbits, Eur. J. Pharm. Biopharm., 52, 159, 2001. 

Intravenously administered diazepam is first-line therapy for status epilepticus. However there is a serious risk for severe respiratory depression, hypotension, bradycardia and cardiac arrest. Rectal administration as micro-clysma can be an attractive alternative, especially in children. 

Prednisone, which in the body is converted to the active form prednisolone, is the most widely used corticosteroid. Maximal activity occurs mostly within 1-2 hours after oral administration, and the effects last up to 36 hours. For patients with colitis localized in the lower part of the colon prednisolone sodium phosphate is formulated for rectal administration as an enema. 

Minimal absorption following oral and rectal administration. Absorbed drug is excreted in urine remainder is eliminated in feces. 

Rectal administration-, burning of rectal mucosa, mild proctitis... 

Pharmacokinetics Readily absorbed from the G1 tract following PO administration. Well absorbed following rectal administration. Protein binding 70%-80%. Metabolized inliveranderythrocytestotheactivemetabolite,trichloroet Hanoi, which may be further metabolized to inactive metabolites. Excreted in urine. Half-life 7-10 hr (trichloroethanol). 

Pharmacokinetics Slowly and incompletely absorbed from the GI tract rapidly and extensively absorbed after rectal administration. Protein binding greater than 90%. Undergoes extensive first-pass metabolism in the liver to active metabolite. Eliminated in feces by the biliary system. Half-life 21 hr. 

Drugs may also be administered locally in the form of bougies, jellies for urethra, pessaries, vaginal tablets, creams and douches for vagina and suppositories for rectal administration. 

Enema are solution, suspension or emulsion (oil/water type) of medicament intended for rectal administration. 

Rectal administration The drug is also administered rectally in the form of suppositories and enema preparations which are absorbed from the colon. 

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