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PubMed1993

Absorption of 2',3'-dideoxyinosine from lower gastrointestinal tract in rats and kinetic evidence of different absorption rates in colon and rectum.

This study explored the rectal route of administration for 2',3'-dideoxyinosine (ddI). Rats were given a rectal infusion of nonradiolabeled ddI (200 mg/kg in 0.7 mL saline) over 35 min along with an intravenous (iv) bolus injection of [8-(3)H]ddI (20 microCi, equivalent to 2.1 micrograms), which was used to calculate the absolute rectal bioavailability of ddI. Maximal plasma concentrations of rectally administered unlabeled ddI were 5.4 +/- 2.2 micrograms/mL and were reached at the end of the infusion. The rectal bioavailability averaged 15.6 +/- 4.4% (n = 9). The second aim of this study was to examine the kinetics of ddI absorption from the colorectal region. Analyses of the absorption rate-time profiles by the Loo-Riegelman and deconvolution methods showed biphasic absorption: a rapid phase during infusion and a slow phase postinfusion. These profiles were inconsistent with a mammillary model with absorption from a single site with one apparent rate constant. The model which gave the best fit for infusion and postinfusion data consisted of two different sites (colon and rectum) with different apparent absorption rate constants. The two sites were connected by a first-order transfer of drug solution from rectum to colon. The apparent absorption rate constant in the rectum was 39-fold higher than that in the colon. In conclusion, these results show absorption of ddI from the colorectal region and suggest the rectal route as an alternative to the oral route. The data further suggest different absorption sites in the colorectal region, with a more rapid absorption in the rectum than in the colon.

Administration, Rectal↗
PubMed1999

Perioperative pharmacodynamics of acetaminophen analgesia in children.

BACKGROUND: There are no adequate pharmacodynamic data relating concentrations of acetaminophen in serum to analgesia. METHODS: Children undergoing outpatient tonsillectomy were administered acetaminophen either orally, 0.5-1.0 h preoperatively (n = 20), or per rectum at induction of anesthesia (n = 100). No other analgesic agents were administered. Individual concentrations of acetaminophen in serum and pain scores (0-10) measured over a 4-h postoperative period were analyzed using a nonlinear mixed-effects model (NONMEM). RESULTS: Mean (% CV) estimates of population pharmacokinetic parameters with percent coefficient of variation, standardized to a 70-kg person, for a one-compartment model with first-order input, lag time, and first order-elimination were a volume of distribution of 60 (21) 1 and a clearance of 13.5 (46) 1/h. Rectally administered acetaminophen had an absorption half-life of 35 (63) min with a lag time of 40 min. The absorption half-life for the oral preparation was 4.5 (63) min without a detectable lag time. The relative bioavailability of the rectal compared with the oral formulation was 0.54. The equilibration half-time of an effect compartment was 1.6 (131) h. Pharmacodynamic population parameter estimates (percent coefficient of variation) for a fractional sigmoidal Emax model, in which the greatest possible pain relief equates to an Emax of 1, were Emax = 1, EC50 (the concentration producing 50% of Emax) = 3.4 (94) mg/l, and Hill coefficient = 0.54 (42). CONCLUSIONS: The pharmacodynamics of acetaminophen can be described using a sigmoidal Emax model with a low Hill coefficient. To achieve a mean posttonsillectomy pain score of 3.6 of 10, an effect compartment concentration of 10 mg/l is necessary.

Acetaminophen↗
PubMed1991

Rectal, buccal, and sublingual narcotics for the management of cancer pain.

We review current knowledge on the rectal, buccal, and sublingual routes of narcotic administration as potential alternatives to oral, intramuscular, intravenous, and subcutaneous administrations of narcotics for the management of cancer pain. Most of the experience reported in the literature is based on the use of rectal, sublingual, and buccal narcotics for the management of acute pain syndromes. Preliminary evidence suggests that both morphine sulfate and chlorhydrate can be administered rectally because there is acceptable absorption with this route even if considerable interpersonal variation exists. There are no controlled trials on the long-term use of rectal morphine for cancer pain. There are very few reports on the clinical effects of sublingual and buccal morphine, and pharmacokinetic data are often debatable. There is evidence to justify further research into all three routes of narcotic administration. At the moment rectal use is justified in clinical trials in cancer patients, but there are not enough data on the pharmacokinetics of different narcotics when administered by the buccal or sublingual routes.

Administration, Buccal↗
PubMed1983

[Pharmacokinetics of an ampicillin suppository (KS-R1) in mice, rats and rabbits].

KS-R1, a new suppository of ampicillin (ABPC) sodium, was rectally administered to study its absorption, excretion and distribution in mice, rats and rabbits. Concentrations of ABPC in plasma when 12.5 and 25.0 mg/kg of KS-R1 were rectally administered to experimental animals reached the peak levels rapidly. The values were 7.3 and 13.9 micrograms/ml in mice, 7.7 and 15.9 micrograms/ml in rats, and 14.1 and 35.3 micrograms/ml in rabbits, respectively. All of these values were about 3.5 times as high as those attained by oral administration of the same doses. Concentrations of ABPC in tissues when 25.0 mg/kg of KS-R1 was rectally administered to rats reached the peak level rapidly, as in the concentration in plasma. The concentrations distributed into various tissues were found as follows; liver not equal to kidney greater than spleen greater than heart greater than lung. Urinary recoveries of ABPC after rectal administration of 12.5 and 25.0 mg/kg were 23.4 and 28.4% (0 approximately 12 hours) in rats while 79.4 and 75.4% (0 approximately 6 hours) in rabbits, respectively. When 25.0 mg/kg of KS-R1 was administered to rats, 10.7% of the dose was excreted into bile during 6 hours after administration. The relative bioavailabilities of KS-R1, calculated on the basis of AUC and urinary recovery after parenteral administration of ABPC sodium, were 81.0 to 87.5% in mice, 37.6 to 45.9% in rats and 75.6 to 101% in rabbits, which were 1.5 to 2.8 times higher than those of ABPC orally administered.

Administration, Oral↗
PubMed1989

Drug absorption through mucosal membranes: effect of mucosal route and penetrant hydrophilicity.

The influence of mucosal route and penetrant hydrophilicity on the in vivo absorption of a model lipophilic compound, progesterone, was investigated in ovariectomized rabbits. The absorption rate and systemic bioavailability of progesterone and its monohydroxy, dihydroxy, and trihydroxy derivatives were evaluated and compared following oral, nasal, rectal, and vaginal administrations. Nasal delivery resulted in a significantly higher rate and extent of progesterone absorption than oral, rectal, or vaginal administration. The rate and extent of mucosal absorption decreased as penetrant hydrophilicity increased for the nasal, rectal, and vaginal routes. The results of this investigation indicate that the absorption characteristics of a lipophilic compound, such as progesterone, are influenced by the properties of both the mucosa and the drug.

Absorption↗
PubMed1986

Enhanced rectal potassium secretion in chronic renal insufficiency: evidence for large intestinal potassium adaptation in man.

The role of the large intestine in K+ excretion in chronic renal insufficiency was studied with a rectal dialysis technique in 14 normal subjects and eight normokalaemic, normotensive patients with chronic renal insufficiency. At initial intraluminal K+ concentrations of 10, 20, 30 and 45 mmol/l, net K+ secretion in patients with renal insufficiency was significantly greater than in normal subjects by approximately 1.8 mumol h-1 cm-2. The increase in net K+ secretion was more marked in those patients with creatinine clearances of less than 10 ml/min. In contrast, there were no significant differences in net Na+ and water transport, transmucosal potential difference and plasma aldosterone concentrations between the two groups. With an initial intraluminal K+ concentration of 30 mmol/l, the addition of amiloride (final concentration 1 mmol/l) to the rectal lumen decreased net Na+ absorption and transmucosal potential difference in normal subjects by 69% (P less than 0.005) and 31% (P less than 0.005) respectively, and in patients with renal insufficiency by 75% (P less than 0.05) and 36% (P less than 0.05) respectively, but there was no change in net K+ secretion in either group. These results indicate that the K+ secretory capacity of the rectal mucosa increases in chronic renal insufficiency, and the large intestine may therefore contribute to the maintenance of K+ homoeostasis as renal K+ excretion declines. Increased rectal K+ secretion in renal insufficiency occurs independently of changes in plasma K+ and aldosterone concentrations, net Na+ absorption and transmucosal potential difference, and may reflect stimulation of an active K+ secretory process.

Adult↗
PubMed1995

[Rectal administration of anesthetic agents].

OBJECTIVES: To collect data in the current literature dealing with the diffusion, the reliability and the effectiveness of the rectal administration of anaesthetic drugs. To evaluate differences with parenteral administration. DATA SOURCES: Pharmacokinetics and clinical studies published in recent years in indexed journals. STUDY SELECTION: Based on the study methodology, drugs employed and pharmacokinetic parameters evaluated. DATA EXTRACTION: Factors involved in absorption of drugs from the rectal mucosa, clinical effect and pharmacokinetic data of the following drugs: diazepam, flunitrazepam, midazolam, ketamin and methohexital, then a brief evaluation of other drugs: thiopental, etomidate, morphine and chloral hydrate. DATA SYNTHESIS: The most widely used drugs are benzodiazepines: they are safe, easy to manage and highly effective; among them midazolam has the best kinetic and dynamic pattern. Ketamin is useful during painful diagnostic procedures; with the use of barbiturates there is a greater risk of respiratory depression and more caution must be employed. CONCLUSIONS: Wide intervariability of rate of absorption, achievement of plasma levels and clinical effect is a relevant drawback of this technique, such to make it not preferable to the parenteral route, when both are feasible. It deserves, anyway, more consideration, and maintains its validity for the preparation of the paediatric patient to general anaesthesia.

Administration, Rectal↗
PubMed1981

Enteral administration of insulin in the rat.

1 The effect of the surfactant, Cetomacrogol 1000, on the absorption of insulin across the rectal mucosa has been studied. 2 Rectal administration of microenemata containing Cetomacrogal 1000 and insulin causes a rise in the plasma concentration of insulin and a consequent fall in the blood glucose concentration in diabetic and non-diabetic rats. 3 The hypoglycaemic response is dependent on both the concentration of surfactant and the dose of insulin administered. 4 The results suggest that the transport of insulin across the rectal mucosa is facilitated by Cetomacrogal 1000.

Animals↗
PubMed1992

[Use of water-soluble beta-cyclodextrin derivatives as carriers of anti-inflammatory drug biphenylylacetic acid in rectal delivery].

To improve the rectal delivery of an anti-inflammatory drug, biphenylylacetic acid (BPAA), the use of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) and heptakis (2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CyD) was investigated. Inclusion complex formations of BPAA with both beta-CyDs in a molar ratio of 1:1 in water were ascertained, and their stability constants were determined. The dissolution of BPAA in water and the release of BPAA from an oleaginous suppository (Witepsol H-5) were significantly increased by beta-CyDs, depending on the magnitude of the stability constants of the water-soluble complexes. However, the serum levels of BPAA after rectal administration of the suppositories containing BPAA or its beta-CyDs complexes in rats increased in the order of BPAA alone much less than DM-beta-CyD less than or equal to HP-beta-CyD complex. The in situ recirculation study revealed that the greater the stability constant of the complex, the lesser was the absorption of BPAA from the rectal lumen of rats under the solution state. Both in vivo and in situ studies demonstrated that rather high amount of HP-beta-CyD (about 20% of dose) was absorbable from the rat's rectum, compared with DM-beta-CyD (less than 5% of dose), suggesting the possibility of the permeation of BPAA through the rectal membrane in the form of HP-beta-CyD complex. Furthermore, DM-beta-CyD and HP-beta-CyD significantly reduced the irritation of the rectal mucosa caused by BPAA after the administration of the suppositories to rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Rectal↗
PubMedDate not supplied

[Bioavailability of acetylsalicylic acid administered orally or rectally in the rabbit].

The aim of this study is to compare the bioavailability of acetylsalicylic acid administered rectally in suppositories form and orally in tablets form to the rabbit. Acetylsalicylic acid was given to 8 males rabbits rectally and orally in a balanced crossover design with 15 days of interval between each study. In blood samples, acetylsalicylic acid is determined by Trinder's method. It has been established that the rectal route has a faster absorption than the oral route however it displayed a more intense first pass effect than that of the oral route.

Administration, Oral↗
PubMedDate not supplied

Bile acid absorption after near-total proctocolectomy in dogs: ileal pouch vs. jejunal pouch-distal rectal anastomosis.

Bile acid malabsorption is often present in patients after near-total proctocolectomy and ileal pouch-anal canal anastomosis, suggesting ileal dysfunction. Experiments were performed in dogs to compare bile acid absorption after a modified procedure, in which a jejunal pouch was interposed between the terminal ileum and the distal rectum, with that after a conventional ileal pouch operation. Fecal bile acid output (equivalent to hepatic bile acid biosynthesis) and composition were determined by gas chromatography/mass spectrometry in five jejunal pouch dogs and in five ileal pouch dogs more than 6 months after operation. Fecal bile acid output in the jejunal pouch dogs (mean +/- standard deviation) was 215 +/- 59 mg/day (10.1 +/- 2.7 mg/kg-day), a value similar to that obtained in the ileal pouch dogs (261 +/- 46 mg/day [12.8 +/- 3.1 mg/kg-day]; P >0.05). These values were also similar to those reported by others for healthy unoperated dogs, indicating that increased bile acid biosynthesis occurring in response to bile acid malabsorption was not present. Fecal bile acids in pouch dogs were completely deconjugated and extensively 7-dehydroxylated (jejunal pouch = 90.4% dehydroxylated; ileal pouch = 88.6% +/- 6.6% dehydroxylated) and consisted predominantly of deoxycholic acid derivatives. We conclude that when either a jejunal pouch or an ileal pouch is used as a rectal substitute in dogs, an anaerobic pouch flora develops that efficiently deconjugates and dehydroxylates bile acids, rendering them membrane permeable. The resultant passive absorption of unconjugated bile acids appears to compensate for any loss of active ileal absorption of conjugated bile acids, and bile acid malabsorption does not occur.

Absorption↗
PubMed1985

Pharmacokinetics of benzydamine.

Clinically, benzydamine can exert its action locally or systemically. Consequently the pharmacokinetics of this drug have been studied after its administration by several different routes. Oral doses of benzydamine are apparently well absorbed and plasma drug concentrations reach a peak fairly rapidly (e.g. 0.8 micrograms/ml after a 100-mg dose) and then decline with a half-life of about 13 h. Less than 20% of the drug is bound to plasma proteins. Assuming complete oral systemic availability, values of 193 ml/min and 213 litres respectively were calculated for the systemic clearance and volume of distribution of benzydamine. Cutaneous doses of benzydamine are more slowly absorbed and lead to peak drug levels about three-fold lower, but more persistent than those after oral administration. Although local drug concentrations are relatively large, the systemic absorption of mouthwash-gargle, vaginal and rectal doses of benzydamine is relatively low compared to oral doses: this lower absorption should greatly diminish the potential for any systemic drug side-effects when benzydamine is administered by these routes. Benzydamine is metabolized primarily by oxidation, conjugation and dealkylation.

Absorption↗