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PubMed1986

The pharmacokinetic profile of clofoctol in rat plasma and tissues after oral and rectal administration.

The pharmacokinetics of clofoctol was investigated in rat plasma and tissues after both oral and rectal treatment at a single dose of 300 mg/kg. After oral administration the plasmatic peak was 2.12 +/- 0.92 microgram/ml, occurring at the 90th min, with T/2 of 121.45 +/- 23.41 min. After rectal administration a plasmatic peak of 1.97 +/- 0.61 microgram/ml was reached at the 20th min with T/2 of 41.07 +/- 12.30 min. The kinetic profile of the drug in tissues exhibited a pattern similar to that in the plasma, since the maximal peak of clofoctol in tissues following rectal administration occurred before that obtained after oral administration. Tissue concentrations significantly higher than plasmatic ones were obtained through both administration routes. The present results indicate that clofoctol is well absorbed after both oral and rectal administration; however rectal treatment produces more rapid absorption and elimination compared with oral treatment.

Animals↗

PubMed2004

Pharmacokinetics of artesunate following oral and rectal administration in healthy Sudanese volunteers.

The aims of this study were to determine the pharmacokinetic parameters of a single dose of 200 mg oral and rectal artesunate in healthy volunteers, and to suggest a rational dosage regimen for rectal administration. The study design was a randomized open cross-over study of 12 healthy volunteers; the analytical method used was a reversed phase high performance liquid chromatography with post column derivatization and subsequent ultraviolet detection. Pharmacokinetic parameters were derived from the main metabolite alpha-dihydroartemisinin data due to the rapid disappearance of artesunate from the plasma. Dihydroartemisinin following oral administration of artesunate had a significantly higher AUC(0-infinity) (P<0.05 95% confidence interval (CI) -1168.73, -667.61 ng x h/mL(-1)) and Cmax (P<0.05; 95% CI -419.73, -171.44 ng/mL(-1)), and had shorter tmax (P<0.05; 95% CI -0.97, -0.10 h) than that following rectal artesunate. There was no statistically significant difference in the elimination half-life between both routes of administration (P>0.05; 95% CI -0.14, 0.53 h). The relative bioavailability of rectal artesunate was [mean (coefficient of variation %) 54.9 (24.8%) %]. On the basis of these data an 8 hourly dosing regimen per day with rectal artesunate is proposed.

Administration, Oral↗

PubMed1994

Tacrine in Alzheimer's disease: pharmacokinetic and clinical comparison of oral and rectal administration.

In a previous pharmacokinetic study in Alzheimer patients great inter-individual variation and low oral bioavailability of the cholinesterase inhibitor tacrine (tetrahydroaminoacridine, THA) were found. In the present investigation oral and rectal administration of tacrine were compared with the aim to find a route for improved bioavailability through diminished first-pass metabolism in the liver. Eight patients suffering from Alzheimer's dementia were given tacrine by oral (25 and 50 mg b.i.d.) and rectal (12.5 and 25 mg b.i.d.) routes for 1 week with 4-6 weeks washout in between. Drug hydroxylation capacity in the patients was determined using the debrisoquine test. Levels of tacrine in plasma and cerebrospinal fluid (CSF) were determined and the cognitive performance was examined by the Mini-Mental State Examination (MMSE) and the Alzheimer Deficit Assessment Scale (ADAS). Tacrine was well tolerated in all but one patient, a slow hydroxylator, who developed an aplastic anemia. MMSE and ADAS scores did not significantly change, except for word recall which was improved on tacrine when given by the rectal route. Pharmacokinetic analysis of the two administration routes revealed that the drug dose may be reduced by almost 50% when given rectally compared to orally. Concentrations of tacrine in the CSF were significantly lower and correlated linearly with the concentrations in plasma.

Administration, Oral↗

PubMed1998

Chronic phenobarbital therapy reduces plasma benzodiazepine concentrations after intravenous and rectal administration of diazepam in the dog.

Disposition of diazepam (DZ) 2 mg/kg after single bolus intravenous (i.v.) and rectal (p.r.) administration before and after 30 day oral phenobarbital therapy was investigated in normal dogs. Adverse cardiovascular and neurologic effects for each drug, dosage and route of administration were evaluated. Plasma benzodiazepine concentrations were determined by fluorescence polarization immunoassay. This assay measured DZ and its active metabolites, oxazepam and nordiazepam to provide a total benzodiazepine concentration. Mean peak plasma concentrations after i.v. administration were 5963 and 5565 ng/mL, before and after phenobarbital treatment, respectively. After p.r. administration, mean peak concentrations were 629 ng/mL and 274 ng/mL and were reached within 30 min before and after phenobarbital treatment, respectively. The target concentration for potential seizure control (i.e. 150 ng/mL) was attained in five dogs in the post phenobarbital p.r. group with a median time to attainment of target concentration of 8 min. The administration of phenobarbital resulted in significantly lower areas under the plasma concentration vs. time curves (AUC) for both i.v. and p.r. administration. Similarly, there was a reduction in maximal plasma concentration, bioavailability (F), mean residence time, and time to target and peak concentrations in the postphenobarbital p.r. group, as compared to the prephenobarbital p.r. group. Adverse cardiovascular and neurologic effects were short-lived and were considered of minor clinical significance. Overall, chronic phenobarbital therapy in the dog reduces total benzodiazepine concentration after i.v. and p.r. administration presumably due to increased hepatic clearance of DZ and its metabolites oxazepam and nordiazepam. Despite this finding, administration of DZ rectally at 2 mg/kg may be a clinically useful alternative to i.v. administration to treat emergency seizures when i.v. therapy is not possible in dogs on chronic phenobarbital therapy.

Administration, Oral↗

PubMed1975

Absorption of 3H-benzocaine from ointments following rectal administration in rats.

Total radioactivity in the blood of rats for 5 hr following rectal administration of 3H-benzocaine in oleaginous, absorption, emulsion (water-in-oil and oil-in water), and water-soluble ointment vehicles was measured. The release was greatest from the water-soluble vehicle and followed the same relative order as seen in an earlier in vitro experiment. No intact benzocaine was found in the blood using radiochromatography. In vitro hydrolysis of benzocaine by rat blood did not occur as determined with the techniques of this experiment.

Administration, Topical↗

PubMed1979

First-pass effect after rectal administration of thiazinamium methylsulfate.

The absorption and metabolism of the quaternary ammonium compound thiazinamium methylsulfate were studied in humans using plasma concentration data and urinary excretion measurements. After giving a dose of 150 mg in suppositories, the relative bioavailability was 5.8 +/- 3.2 (SD) % of the dose, comparable to the values obtained following oral administration. The degree of first-pass effect observed after rectal administration was comparable with that after oral administration.

Aged↗

PubMed1982

Bioavailability of diazepam after intravenous, oral and rectal administration in adult epileptic patients.

1 The absorption of single doses of diazepam in six adult epileptic subjects following intravenous, oral and rectal administration were studied in order to evaluate the usefulness of the latter in emergency situations in the adult. 2 Diazepam tablets (Valium, Roche) and rectal solution (Valium solution for intravenous administration) produced similar peak serum concentrations after delays of 15-90 min. 3 Two suppository formulations showed statistically significant differences in absorption characteristics. 4 Serum diazepam levels above 400 ng ml-1 (suggested to be necessary for a satisfactory anticonvulsant effect) were reached in only a few subjects after rectal doses of 10-20 mg of solution, and then usually after a delay of over 2 h.

Administration, Oral↗

PubMed1996

Pharmacodynamic activity (leukopoietic effect) of recombinant human granulocyte colony-stimulating factor (rhG-CSF) after rectal administration in rabbits with leukopenia induced by cyclophosphamide.

The pharmacodynamic activity (leukopoietic effect) and pharmacokinetics of recombinant human granulocyte colony-stimulating factor (rhG-CSF) administered in various doses as hollow-type suppositories were investigated in rabbits with leukopenia induced by cyclophosphamide (CPA-treated rabbits). We found that serum granulocyte colony-stimulating factor (G-CSF) concentration was increased following the rectal administration of rhG-CSF. Therefore, rhG-CSF could be absorbed from the rectal mucosa in leukopenic rabbits who received CPA at a dose of 30 mg/kg/d. When rhG-CSF of at least 300 micrograms/kg was administered rectally once a day for 3 d in CPA-treated rabbits 1 d after the induction of leukopenia (the total count of leukocytes in peripheral blood [total blood leukocyte count] was below 5000/microliter), decreased total blood leukocyte count returned to the normal physiological level and a maximum (7000-16000/microliter) was obtained 3 d after the start of the rhG-CSF multiple-dosing regimen. We report for the first time that rhG-CSF administered rectally induces leukopoiesis in CPA-treated rabbits and reduces the period of leukopenia induced by CPA. Thus, the rhG-CSF hollow-type suppository offers a promising means of reducing the risk of leukopenia, an adverse side effect of CPA therapy.

Administration, Rectal↗

PubMed1993

Plasma concentrations of midazolam after i.v., nasal or rectal administration in children.

Midazolam is used frequently for premedication in children, preferably by non-parenteral administration. We have compared plasma concentrations of midazolam after nasal, rectal and i.v. administration in 45 children (aged 2-9 yr; weight 10-30 kg) undergoing minor urological surgery. General anaesthesia consisted of spontaneous respiration of halothane and nitrous oxide in oxygen via a face mask. After administration of atropine and fentanyl i.v., children were allocated randomly to receive midazolam 0.2 mg kg-1 by the nasal, rectal or i.v. route. In the nasal group, children received 50% of the dose of midazolam in each nostril. In the rectal group, midazolam was given rectally via a cannula. Venous blood samples were obtained before and up to 360 min after administration of the drug. Plasma concentrations of midazolam were measured by gas chromatography and electron capture detection. After nasal and rectal administration, midazolam Cmax was 182 (SD 57) ng ml-1 within 12.6 (5.9) min, and 48 (16) ng ml-1 within 12.1 (6.4) min, respectively. Rectal administration resulted in smaller plasma concentrations. In the nasal group, a plasma concentration of midazolam 100 ng ml-1 occurred at about 6 min. After 45 min, the concentration curves after i.v. and nasal midazolam were similar.

Administration, Intranasal↗

PubMed1989

Sustained blood concentration of salicylic acid following rectal administration of salicyluric acid in dogs.

The blood concentrations of salicyluric acid and salicylic acid following rectal, intravenous and oral administrations of salicyluric acid (5, 10 and 60 mg/kg, respectively: salicylic acid equivalent) were determined in dogs. After rectal administration, a small amount of salicyluric acid was absorbed in intact form. The rest was hydrolyzed to salicylic acid, which was subsequently absorbed. The blood concentration of salicylic acid was maintained at 0.4-0.7 microgram/ml from 2 to 12 h. Following intravenous administration of salicyluric acid, salicyluric acid was detected in the blood but was rapidly eliminated. A trace amount of salicylic acid was detected, suggesting that systemic de-conjugation of glycine was involved. After oral administration of salicyluric acid, salicyluric acid was well absorbed. Salicylic acid was detected at low concentration for 12 h. Species difference in the metabolic fate of salicyluric acid in dogs, rabbits, rats and humans reported previously is discussed.

Administration, Rectal↗

PubMed2000

Enhanced absorption of indomethacin after oral or rectal administration of a self-emulsifying system containing indomethacin to rats.

A self-emulsifying system (SES), a mixture of an oil and a surfactant which forms an oil-in-water emulsion, is expected to improve the in vitro drug dissolution and enhance the in vivo drug absorption. In this study, a poorly water-soluble drug, indomethacin (IDM) was incorporated into the SES to increase bioavailability. The SES with 30% of Tween 85 and 70% of ethyl oleate, EO (w/w) was selected as an optimized formulation (high drug loading, low surfactant concentration, and small particle size). After an oral administration of the SES containing IDM and IDM suspension, (IDM was suspended in methyl cellulose), 22.5 mg/kg as IDM, to rats, the area under the plasma concentration-time curve from time zero to the last measured time in plasma, 12 h (AUC(0-12 h)) was significantly greater (57% increase) in the SES, suggesting that oral absorption of IDM increased significantly by the SES. After a rectal administration of gelatin hollow type suppositories, filled with the SES containing IDM and IDM powder physically mixed with the SES, 22. 5 mg/kg, to rats, the AUC(0-12 h) also increased significantly (41% increase) by the SES, suggesting that rectal absorption of IDM also increased significantly by the SES.

Administration, Oral↗

PubMedDate not supplied

The rectal administration of MS Contin: clinical implications of use in end stage cancer.

Mercy Hospice in Nampa, Idaho administered unmodified MS Contin 30 mg tablets rectally to 39 terminally ill patients. All patients had pain controlled on oral MS Contin but were switched to the rectal route of administration because of intractable nausea, inability to swallow or both. Pain control was maintained on all patients receiving rectal MS Contin. In 11 patients, the dosage of MS Contin was decreased. No local or systemic adverse reactions developed. The rectal administration is a safe, effective and simple means of maintaining pain control in terminally ill patients.

Administration, Rectal↗

PubMed1983

Absorption and excretion of azodisal sodium and its metabolites in man after rectal administration of a single 2-g dose.

The behaviour of azodisal sodium (ADS) and its metabolites after a single 2-g rectal dose was investigated in 10 healthy volunteers. Blood samples were drawn frequently, and urine was collected during intervals of 24 h. The ADS absorption gave a mean peak serum concentration of 2.1 (SD +/- 0.7) microgram/ml. The urinary excretion of ADS was 0.8% of the given dose. After rectal administration 5-aminosalicylic acid (5-ASA) could be detected in the serum only in two of the subjects, with a mean concentration of less than 0.5 microgram/ml. Ac-5-ASA was present in increasing serum concentrations, being 0.93 microgram/ml at 24 h. The mean 24-h urinary excretion of these two metabolites was only 2.7% of the given dose. In another study the azo bond of ADS has been shown to be split by anaerobic and aerobic bacteria. The low absorption of its metabolites indicates that ADS is a suitable molecule for delivering the presumed pharmacologically active moiety, 5-ASA.

Adult↗

PubMed1981

Serum and saliva levels of 8-methoxypsoralen after rectal administration as a micro-enema.

Serum and saliva concentrations of 8-methoxypsoralen (8-MOP) were determined in seven healthy human volunteers after rectal administration of a micro-enema. High peak serum levels were reached very soon(0.7 + or - 0.3 h) after administration of 8-MOP. Nausea was not experienced. There was a reasonable good linear correlation between 8-MOP concentrations in saliva and serum (r = 0.937). The saliva/serum ratio for 8-MOP concentration was 0.08 +/- 0.02.

Enema↗

PubMed1977

Plasma-diazepam in infants after rectal administration in solution and by suppository.

Twenty infants aged 1-2 years who had previously had one attack of febrile convulsions were randomly given a single dose of diazepam rectally, either as a solution (0.7 mg/kg) or by suppository (5 mg). Plasma-diazepam levels were determined repeatedly during the first hour using gas chromatography. Rectal administration of diazepam in solution resulted in anticonvulsant plasma values within 4 +/- 1 min. Similar plasma levels were obtained only after 20-30 min in the group treated with suppositories. Diazepam in solution given rectally may therefore be useful in the acute treatment of febrile convulsions, while treatment by suppository would seem to be of little value in this respect. Moreover, diazepam in solution given rectally seems suitable for use at home in case of recurrent febrile convulsions. This treatment, however, cannot be recommended until the anticonvulsant effect and side-effects have been elucidated further.

Child, Preschool↗

PubMed1989

[Pharmacokinetic studies following intravenous and rectal administration of midazolam in children].

UNLABELLED: In children, rectal midazolam is being used increasingly for premedication, as this substance is reported to have a short half-life and rapid action. Above all it is the only known diazepam derivative with a good correlation of plasma concentration and clinical action despite its receptor binding capacity. As pharmacokinetic data in children are lacking and different dose regimens for rectal premedication exist, we studied plasma concentrations in 3 groups of children. METHODS. After obtaining informed parental consent we studied children aged 3-7 years (15-30 kg body weight) ASA I status scheduled for minor elective surgery. Group 1 (n = 6) received 0.1 mg/kg midazolam i.v. for induction of anesthesia. Group 2 (n = 10) was premedicated with 0.35 mg/kg midazolam, instilled just behind the anal sphincter; group 3 (n = 5) received 0.5 mg/kg midazolam rectally. Blood samples were drawn up to 120 min after application. The anesthesia technique consisted of N2O/O2, enflurane, intubation and the use of muscle relaxants, if necessary. Midazolam plasma levels were measured by HPLC. RESULTS. There were no differences with respect to age or body weight. Group 1: half-life in children was shorter than in adults, Vdss was smaller and clearance identical. Group 2: Rectal midazolam 0.35 mg/kg has a remarkably short onset of action with peak plasma concentrations (71 ng/ml) in the range of sedative levels in adults occurring in 7.5 min. After 2 h they reached levels of 30 ng/ml. Group 3 patients had peak levels of midazolam of 246 ng/ml after 12.5 min, falling to an average concentration of 120 ng/ml after 2 h. The bioavailability of rectal midazolam, comparing the area under the median curves, is 4.7% in group 2 and 16.1% in group 3. CONCLUSIONS: The pharmacokinetics of midazolam in our patients showed a shorter half-life, probably due to the higher hepatic clearance based on the high CI in children, as midazolam is known to have a first-pass effect of 30-70%. The increased metabolic transformation and the smaller amount of fatty tissue accounts for the smaller Vdss in children compared to adults. Rectal midazolam has a remarkably short onset and especially in a dose of 0.5 mg/kg prolonged action due to ongoing resorption from the rectum as demonstrated by the clinically relevant plasma concentrations. This fact must be taken into consideration in the overall anesthesia management.(ABSTRACT TRUNCATED AT 400 WORDS)

Administration, Rectal↗

PubMed1981

Rectal administration of theophylline in aqueous solution.

Theophylline has a narrow therapeutic index which complicates rapid effective administration. Therapeutic serum levels without toxic concentrations can usually be achieved only by a 20 min intravenous administration. In the present study 20 children were given a single dose of theophyllinne in aqueous solution rectally. Serum theophylline levels were determined, and they equalled those found after a 20 min intravenous infusion of theophylline. No adverse effects were observed. The variations in peak serum levels were the same as those reported after intravenous administration. Therefore rectal administration of an aqueous solution of theophylline may become a valuable alternative to the intravenous route. The procedure is simple, can be used at home by the parents even in cases of nausea and vomiting, and an accurate dosage calculated in mg/kg is possible. This treatment, however, cannot be recommended until further investigations have been carried out.

Asthma↗

PubMed1987

Absolute bioavailability of hydromorphone after peroral and rectal administration in humans: saliva/plasma ratio and clinical effects.

The absolute bioavailability of hydromorphone was investigated in eight healthy male subjects by a cross-over design (with washout period of two weeks) after intravenous (2 mg), peroral (4 mg) and rectal (3 mg) administration of hydromorphone. The use of saliva hydromorphone concentrations as a noninvasive technique in pharmacokinetic evaluation was investigated, and the clinical effects after the three routes of administration were determined. Hydromorphone has an absolute bioavailability of 51.35 +/- 29.29% and 36.33 +/- 29.60% after peroral and rectal administration, respectively. More side effects were observed after intravenous administration of hydromorphone than after rectal or peroral dosing. The saliva sampling for the hydromorphone concentration was found to be a useful noninvasive technique for the estimation of the elimination half-life of hydromorphone.

Administration, Oral↗