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At least 19 recordsLinked to original sources
PubMed1986

Comparison of bioavailability in man of tamoxifen after oral and rectal administration.

The bioavailability of tamoxifen from 40 mg suppositories was tested in six male volunteers and compared with that of tamoxifen (Nolvadex) tablets. Plasma concentrations of tamoxifen and its major metabolites, 4-hydroxytamoxifen and N-desmethyltamoxifen, were measured by extraction from plasma obtained at different times after administration, separated by HPLC, converted on-line to fluorescent phenanthrene derivatives and quantified with a fluorescence detector. The mean relative bioavailability from the suppositories was 28%; the addition of a surfactive agent diminished the bioavailability to 13%. Simulation of repeated administration of 40 mg suppositories suggests a mean steady state plasma concentration for tamoxifen of approximately 70 ng ml-1, i.e. 30% of the steady state value after simulated oral administration. Rectal administration of tamoxifen leads to a lower bioavailability than that by oral administration and therefore cannot be recommended when used in equivalent doses.

Administration, Oral↗
PubMed1977

Studies on the absorption and disposition of meptazinol following rectal administration.

1 Rectal administration of the new analgesic drug, meptazinol, resulted in rapid absorption of the compound both in the monkey and in man. Peak plasma levels were observed within 0.5 h of dosing. 2 Absorption of the drug following rectal administration was extensive as shown by the recovery of 65-90% of the dose in the urine. 3 Despite substantial inter-individual variation in the observed maximum plasma concentrations of the drug, it was still evident that concentrations after rectal dosage were considerably higher than when the same dosage was given orally. 4 Elimination of the drug from plasma took place rapidly in an apparently mono-exponential manner in both species. The half-life of elimination in monkeys was 1.25 h and in man 2.0 h.

Adult↗
PubMed1983

Plasma concentrations of atropine after rectal administration.

The rectal administration of the premedication for children is often preferred in order to minimise discomfort. The appropriate dose of atropine when rectally administered is poorly documented. In this study six children weighing between 7.5 and 41 kg were given 0.02 mg atropine sulphate/kg rectally and four children were given the same doses intramuscularly. Plasma concentrations of atropine were analysed at several intervals after administration by a modified mass fragmentographic method accurate to 0.1 ng/ml. Peak plasma concentration of atropine, reached after 15 minutes, was 0.7 ng/ml, compared with 2.40 ng/ml reached after 5 minutes for the intramuscular route. The relation between intramuscular and rectal peak concentration was 3.2:1.

Atropine↗
PubMed2001

Glutathione uptake after intraperitoneal administration and glutathione radiopharmacology after rectal administration, in mice.

Glutathione is a biologic aminothiol radioprotector. Hydrolysis of exogenous glutathione takes place in the extracellular compartment and leads to two metabolites: gamma-glutamylcysteine and glycine. In healthy mice, after an intraperitoneal administration of glutathione, all organs absorb the gamma-glutamylcysteine and the glycine with variable kinetics according to their enzymatic equipment. The rectal administration of glutathione in mice previously irradiated at the pelvic region, increases the availability of glutathione in the rectum and in other organs at a distant from the irradiation site. This contribution could be used to protect the rectum and the uterus during therapeutic irradiation.

Administration, Rectal↗
PubMed1993

Bioavailability and diuretic effect of bumetanide following rectal administration of suppositories containing weak acids in human subjects.

The bioavailability of bumetanide following the oral administration of tablets, or the rectal administration of either macrogol suppositories or suppositories with and without weak acids were evaluated in human subjects. The absorption of bumetanide from those suppositories containing bumetanide without weak acids (control suppositories) was extremely poor, while the absorption from those suppositories containing citric acid or tartaric acid was enhanced. The mean area under the plasma concentration-time curve (AUC) following the rectal administration of the suppositories containing citric acid and tartaric acid was 52 and 62%, respectively, of that following the oral administration. On the other hand, the absorption rate constant (ka) and the mean residence time (MRT) following the rectal administration of the suppositories containing weak acids increased significantly compared to those administered orally. The time (Tmax) required to achieve the maximum plasma concentration (Cmax) in the plasma following the rectal administration of the suppositories containing weak acids was significantly shortened compared to the time of those administered orally. These results indicated that the bumetanide contained in the suppositories containing weak acids might be absorbed rapidly after administration. The diuretic effect of bumetanide following the oral and rectal administration was also evaluated. Sufficient diuretic effects were obtained following the rectal administration of the suppositories containing weak acids.

Administration, Oral↗
PubMed1993

[Comparison of bioavailability of salbutamol between oral and rectal administration in rabbits].

In order to obtain a basic knowledge for developing the rectal dosage form of salbutamol (SB), a comparison of the bioavailability was made between oral and rectal administrations. After the intravenous, oral and rectal dosing of SB solution in rabbits, SB and its glucuronide (SBG) in plasma and urine were determined. The bioavailability estimated by the area under the blood concentration-time curve (AUC) of SB from 0 to 9 h after oral and rectal administrations were 1.1 +/- 0.5% and 7.8 +/- 2.2% (mean +/- S. E., n = 5), respectively. Percent of dose excreted in urine as total SB (SB+SBG) 10 h after oral and rectal administrations were 77.3 +/- 3.82% and 9.80 +/- 0.15% (mean +/- S. E., n = 3), respectively, which indicating relatively good oral and poor rectal SB absorption. A partial avoidance of first-pass-effects might contribute to higher bioavailability after the rectal administration.

Administration, Oral↗
PubMed1986

Plasma concentrations of clonazepam after single rectal administration.

Clonazepam was administered rectally to six children aged 1.4 to 4.7 years in a dose of 0.05 mg/kg and to five children aged 1.4 to 4.1 years in a dose of 0.1 mg/kg. Plasma concentrations indicate that it is rapidly absorbed, and it may therefore be an alternative to rectal administration of diazepam in continuing convulsions.

Benzodiazepinones↗
PubMed1985

Methohexital plasma concentrations in children following rectal administration.

Despite the increasing use of rectal methohexital as a premedicant-induction agent in pediatric anesthesia, there are no data to confirm the assumption that low plasma methohexital concentrations are the cause of inadequate sedation of children and that high concentrations are associated with the loss of consciousness. Plasma methohexital concentrations were determined in 20 ASA Class I children, ages 2-7 yr, after the rectal administration of methohexital (25 mg/kg). Seventeen of the 20 children in this study fell asleep after receiving the drug and achieved peak plasma concentrations greater than 2 micrograms/ml. The maximum plasma methohexital concentration in children that did not fall asleep was less than 2 micrograms/ml. The mean time to the onset of sleep after drug administration was 8.3 min (at which time the mean plasma concentration was 4.4 micrograms/ml). The mean peak plasma concentration and the mean time to peak plasma concentration were 4.7 micrograms/ml and 13.9 min, respectively. Loss of consciousness after rectal administration of methohexital correlates well with the plasma concentration of the drug.

Anesthesia, Inhalation↗
PubMed1985

Bioavailability of indomethacin after intramuscular injection and rectal administration of solution and suppositories.

The pharmacokinetics of indomethacin was studied after intravenous and intramuscular injection of 50 mg and administration of rectal solution and suppositories of 100 mg to 8 volunteers. Peak plasma concentrations of indomethacin occurred 20 min. after administration of the rectal solution (3.7 micrograms X ml-1), 40 min. after intramuscular injection (2.7 micrograms X ml-1), and 60 min. after suppositories (3.7 micrograms X ml-1). The bioavailability after the two rectal forms was found to be almost the same, about 80%. After intramuscular injection the bioavailability was calculated to be complete. These results suggest that indomethacin administered as a rectal solution or as intramuscular injection may be an alternative to intravenous administration when an early plasma peak of the drug is required.

Adult↗
PubMed1995

[Rectal administration of ash bark].

A TLC-densitometric method was applied to determine aesculin in rabbit blood. The best way for ash bark rectal administration was found by orthogonal design [L4(2(3))]. The two routes of administration (per rectal, P.O.) were compared by bioavailabilities and the result indicated that per rectal was better than P.O. Modified isolated rectum-bag method was applied successfully to finding the best way for rectal administration of ash bark.

Administration, Rectal↗
PubMed2006

Perception of pain following rectal administration of morphine in children: a comparison of a gel and a solution.

BACKGROUND: Rectal administration of morphine is one possible route of delivery in children. The aim of this study was to determine the pain experience during rectal administration of two different morphine preparations. METHODS: The acceptance of the pain of rectal administration of morphine for premedication was studied in 120 children. Children were randomized to receive either morphine solution in saline (0.2 mg.kg(-1), 1 mg.ml(-1)) or morphine gel (0.2 mg.kg(-1), 1 mg.ml(-1)) with an adjusted pH for rectal use in a double-blind fashion. Children were stratified into three groups according to age (1-2, 3-6, and 7-10 years). Pain was assessed with the Children's Hospital of Eastern Ontario Pain Scale, the McGrath Facial Affective Scale, or the visual analogue scale, depending on the age group. RESULTS: The overall pain scores in all age groups were low. Children aged 1-2 years (P < 0.01) and 3-6 years (P < 0.05) had significantly less pain when morphine was administered as a gel than a solution. The difference in pain experience between the two forms was not significant in the age group of 7-10 years. CONCLUSION: The results indicate that most of the children tolerated rectal administration of morphine well in terms of pain experience, in both gel and solution form. The morphine gel, intended for rectal use appears to be the preparation of choice in children aged 1-6 years.

Administration, Rectal↗
PubMed1993

Serum concentration and cardiovascular effects of salbutamol after oral and rectal administration in healthy volunteers.

In order to evaluate rectal administration of salbutamol (SB), five healthy volunteers were dosed orally and rectally with racemic SB (0.1 mg/kg) solution. Compared with the oral SB, the rectal SB gave significantly higher serum SB concentration immediately after dosing but slightly lower levels in the elimination phase. The Cmax following rectal administration was 17.9 ng/ml (17.0 ng/ml for oral administration), the tmax 0.67 h (1.5 h for oral administration) and the AUC 98.2 ng/ml/h (100 ng/ml/h for oral administration). Heart rate also rose more rapidly to a maximum of 70% above baseline values after rectal dosing. The rate continued to be twice larger than after oral dosing for up to 5 h. The concentration versus response curves indicated that rectal SB was more effective than oral SB at increasing heart rate at the same SB concentration in serum. A plausible explanation for this phenomenon might be a difference in the stereo-selective first-pass metabolism of the two enantiomers. Therefore, the rectal dose of SB administered as a suppository for prophylactic treatment of asthma should be lower than that used orally.

Administration, Oral↗
PubMed1988

Further studies on the hydrolysis of salicyluric acid in intestinal microorganisms and prolonged blood concentration of salicylic acid following rectal administration of salicyluric acid in rabbits.

The blood concentrations of salicyluric acid and salicylic acid following intracecal and rectal administration of salicyluric acid were determined in rabbits. Immediate and very extensive salicylic acid formation in the cecum was found following intracecal administration. After rectal administration, a small amount of salicyluric acid was absorbed in intact form. The rest was rapidly hydrolyzed to salicylic acid, which was subsequently absorbed. The blood concentration of salicylic acid was maintained at 1.3-1.8 micrograms/ml from 2 to 12 h. Three doses of salicyluric acid were administered rectally. The peak level of salicyluric acid increased with dose. However, salicylic acid concentration in the blood following administration of salicyluric acid at 10.0 mg/kg (salicylic acid equivalent) was not double that observed following administration of salicyluric acid at 5.0 mg/kg (salicylic acid equivalent). It appears that a larger amount of salicyluric acid in the rectal lumen may have saturated the glycine deconjugation system.

Administration, Rectal↗
PubMed1997

Failure of absorption of baclofen after rectal administration.

We wished to determine the degree to which baclofen was absorbed from an aqueous vehicle after rectal administration. A comparison was made to absorption after oral administration. After oral administration, the baclofen half-life was 2.3 to 3.4 hours and peak serum concentrations were achieved from 1 to 2.1 hours after administration. No measurable absorption was observed after rectal administration of the drug in any subject. Rectal administration of baclofen is not a clinically sound treatment option when oral administration of the drug is not possible. For patients receiving chronic baclofen therapy, other medications such as a benzodiazepine should be considered at times when oral administration of medication is not possible.

Absorption↗
PubMed1995

Absorption of diazepam after its rectal administration in dogs.

A cross-over study was performed in 6 healthy mixed-breed dogs and 4 healthy Beagles. Diazepam was administered per rectum to Beagles (0.5 mg/kg of body weight) and mixed-breed dogs (2 mg/kg), and IV (0.5 mg/kg) to both groups of dogs. Each dog received the drug by both routes, with a 1-week washout period between dosages. After diazepam administration, blood samples were collected to measure plasma concentration of diazepam and its active metabolites, desmethyldiazepam and oxazepam, by use of reverse-phase high-performance liquid chromatography (HPLC). Systemic availability was assessed by comparing the area under the curve for diazepam metabolites for each route of administration. Mean (+/- SD) diazepam concentrations in plasma after rectal administration were low in comparison with those obtained after IV administration, with systemic availability of only 7.4 (+/- 5.9) and 2.7 (+/- 3.2)% for the high and low dose, respectively. However, diazepam was converted to its metabolites within minutes after administration. Accounting for the total concentration of benzodiazepines (diazepam plus desmethyldiazepam and oxazepam) in plasma, systemic availability was 79.9 (+/- 20.7) and 66.0 (+/- 23.8)% for the high and low dosage, respectively. After IV administration, diazepam concentration decreased, with a half-life of only 14 to 16 minutes, but desmethyldiazepam and oxazepam concentrations decreased more slowly, with a half-life of 2.2 to 2.8 hours and 3.5 to 5.1 hours, respectively. Each of the metabolites is reported to have anticonvulsant activity. After rectal administration of the high dose, mean total benzodiazepine concentration was above 1.0 microgram/ml within 10 minutes and was maintained above this concentration for at least 6 hours. We conclude that diazepam is absorbed after rectal administration in dogs, and that the pharmacologic effects are probably caused by the active metabolites, not the parent drug. Samples also were analyzed by use of a nonspecific commercial benzodiazepine fluorescence polarization immunoassay (FPIA). Correlation between the FPIA and HPLC assay was strongest for diazepam (R2 = 0.84), weak for desmethyldiazepam (R2 = 0.09), and nonexistent for oxazepam. We conclude from a comparison of assays that HPLC is preferred over the FPIA method for measuring benzodiazepines in dogs.

Absorption↗
PubMed1991

[Rectal administration of drugs. Fundamentals and applications in anesthesia].

Rectal administration of drugs has become a standard procedure in clinical anesthesia, most notably for anorectal induction in children. Limitations of this method include low bioavailability, a wide scatter of pharmacokinetic and pharmacological results, and poor predictability of the clinical effect in any particular patient. Historically, the rectal route has been used for the administration of smoke ("fumigation") for resuscitation and various other purposes. An ether boiler for rectal application was developed by Pirogoff as early as 1847. The pharmacokinetics of rectally administered drugs are determined by the anatomical properties of the rectum and, owing to interindividual variance, this adds to the inconsistency of absorption. Aspects that can be better controlled include the drug preparation and the vehicle, with hydrophilic solutions resulting in improved absorption. Larger volumes such as are associated with lower concentrations increase the bioavailability by enlarging the mucosal surface in contact with the drug. In contrast to the hypothetical assumption that hepatic circulation may be circumvented--thus avoiding first-pass metabolism--by direct venous drainage from the rectum into the systemic circulation via the vena cava, it has been shown that hepatic clearance is the main factor affecting bioavailability. This may be due to blood flow through anastomoses interconnecting the superior, medium and inferior rectal venous systems. Resorption from the rectum is also determined by physicochemical properties of drugs. According to the pH-partition hypothesis, only the non-ionized moiety of a compound will be available for transmucosal diffusion. The degree of ionization is a function of the local (or microclimate) milieu pH and pKa of the drug; the former is close to neutral in adults but alkaline in most children. Adsorption of feces, intraluminal degradation by microorganisms, metabolism within the mucosal cell, and lymphatic drainage do not significantly affect the fate of rectally administered drugs. In clinical practice, the rectal administration of methohexital and midazolam is an established method of premedication or induction of anesthesia in children; so far, midazolam appears to be associated with fewer complications. Ketamine has been shown to be as effective and as quick-acting as methohexital, but at least in one study its use as sole induction agent was associated with respiratory distress in some cases. However, painful diagnostic or therapeutic procedures in children may be indications for the rectal administration of ketamine. Early trials with rectally administered etomidate have been abandoned since its implication in suppression of cortisol synthesis. Narcotic analgesics in a hydrogel vehicle are effective in adult pain management.(ABSTRACT TRUNCATED AT 400 WORDS)

Administration, Rectal↗
PubMed1990

The pharmacokinetics of artemisinin after oral, intramuscular and rectal administration to volunteers.

The pharmacokinetics after oral, intramuscular and rectal administration of artemisinin, a new potent antimalarial drug, to healthy volunteers has been examined. The study was set-up as a four-way cross-over design with a wash-out period of one week between the test days. In ten volunteers artemisinin concentrations in serum were monitored using a reversed phase HPLC assay with UV detection after derivatization. After oral administration, artemisinin was rapidly but incompletely absorbed, the mean absorption time was 0.78 h and the bioavailability relative to the intramuscularly injected suspension in oil 32%. The mean residence time of the latter (10.6 h) was 3 times that of the oral formulation (3.4 h). This seems to enable a twice daily dosage regimen for the intramuscular oil injection, while the oral formulation necessitates a more frequent dosing interval. After intramuscular injection and rectal administration of an aqueous suspension, very low and variable artemisinin concentrations in serum were observed, probably indicating a poor and erratic absorption.

Administration, Oral↗