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  • 1
    ISSN: 1573-904X
    Keywords: regional drug absorption ; gamma scintigraphy ; remote control capsule ; non-invasive
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Evaluate a prototype Remote Drug Delivery Capsule (RDDC) for use in beagle dogs and human volunteers for non-invasive drug absorption studies in different regions of the gastrointestinal tract. Methods. The device was dual radiolabeled and GI transit of the RDDC was monitored by gamma scintigraphy. Beagles were used initially to demonstrate the functional utility of the device where a solution of ranitidine hydrochloride (150 mg) was non-invasively delivered to the stomach, proximal small intestine and distal small intestine. A subsequent first time in human study enrolled twelve healthy male volunteers where the intended site of release was the stomach, early small bowel, distal small bowel or colon. Results. Preliminary studies conducted in beagles indicated that the RDDC operated successfully and the onset of ranitidine serum levels were dependent on the time of capsule activation and site of drug release. Results from the human study showed that all twelve subjects swallowed the device with no discomfort. Mean gastric emptying of the RDDC was 1.50 ± 1.28 h (range = 0.25 to 4.25 h), and total small intestine transit was 4.79 ± 1.82 h (range = 2.00 to 8.25 h). The capsule was retrieved from the feces at 30.25 ± 15.21 h (range = 14.12 to 74.25 h) and there were no reported adverse events. The prototype RDDC operated successfully in nine of the twelve human volunteers and the cause for the three failures was attributed to mechanical failure while the electronics assembly performed favorably. Conclusions. This prototype remote control capsule was shown to be well tolerated and functional to use in human volunteers as well as beagles. The application of the device coupled with gamma scintigraphy has the potential to be a valuable and rapid method to non-invasively evaluate regional drug absorption in the gastrointestinal tract under conditions that are both pharmaceutically and physiologically meaningful.
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  • 2
    ISSN: 1573-904X
    Keywords: neutron activation ; erbium-171 ; samarium-153 ; gamma scintigraphy ; dual-isotope imaging ; dual-labeled dosage forms ; radiolabeled dosage forms ; bilayer tablet ; compton scatter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-904X
    Keywords: neutron activation ; erbium-171 ; erythromycin ; drug delivery system ; gamma scintigraphy ; radiolabeled dosage forms ; scanning electron micrography ; erythromycin dissolution ; erythromycin antimicrobial activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract To evaluate the effects of a neutron activation radiolabeling technique on an enteric-coated multiparticulate formulation of erythromycin, test quantities were produced under industrial pilot scale conditions. The pellets contained the stable isotope erbium oxide (Er-170), which was later converted by neutron activation into the short-lived gamma ray-emitting radionuclide, erbium-171. In vitro studies indicated that the dissolution profile, acid resistance, and enteric-coated surface of the pellets were minimally affected by the irradiation procedure. Antimicrobial potency was also unaffected, as determined by microbiological assay. Neutron activation thus appears to simplify the radiolabeling of complex pharmaceutical dosage forms for in vivo study by external gamma scintigraphy.
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  • 4
    ISSN: 1573-904X
    Keywords: ranitidine ; effervescent tablet ; absorption ; bioavailability ; bioequivalence ; sodium acid pyrophosphate ; gastrointestinal transit time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract During development of a ranitidine effervescent oral solution dosage form, a marked decrease was observed in the extent of ranitidine absorption relative to the conventional oral tablet. Two studies were conducted in healthy volunteers to confirm the involvement of an excipient, SAPP (sodium acid pyrophosphate), and the mechanism of interaction, altered gastrointestinal transit. The first study (n = 12) involved single-dose crossover comparisons of (A) 150 mg ranitidine with 1132 mg SAPP versus (B) 150 mg ranitidine and (C) 150 mg ranitidine with all the effervescent tablet excipients except SAPP versus (D) a 150-mg ranitidine effervescent tablet, all administered as oral solutions. Serum ranitidine AUC, C max, and t max were compared using two one-sided t test 90% confidence intervals (CI). Comparing treatments A to B and D to C, all 90% CI were below the 80–120% range, indicating significantly less extensive ranitidine absorption (54% based on AUC) from the oral solutions containing SAPP. The second study (n = 12) was a single-dose crossover comparing 50 µCi 111InCl solutions with and without 1132 mg SAPP. Gastrointestinal transit times, determined by scintigraphic imaging, were compared between treatments. Gastric emptying time was unchanged, but small intestinal transit time was decreased to 56% in the presence of SAPP. More rapid small intestinal transit associated with an excipient of a solution dosage form apparently resulted in a decreased extent of ranitidine absorption. This observation contradicts the conventional wisdom that oral solutions are unlikely to fall short of bioequivalence relative to solid oral formulations.
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  • 5
    ISSN: 1573-8744
    Keywords: avitriptan ; bioavailability ; gastric emptying ; gamma scintigraphy ; samarium-153 ; gastrointestinal transit ; serotonin agonist ; food effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The study was conducted to assess the bioavailability of avitriptan after a standard high fat meal, in relation to gastrointestinal transit. Six healthy male subjects were enrolled in a four-period study with a partial replicate design where each was administered 150-mg avitriptan capsule (i) after an overnight fast, (ii) 5 min after a standard high-fat breakfast, and (iii) 4 hr after a standard high fat breakfast. The treatment administered in Period 3 was repeated in Period 4 to assess intrasubject variations in pharmacokinetics and gastrointestinal (GI) transit. Avitriptan capsules were specially formulated with nonradioactive 152 samarium chloride hexahydrate which was neutron-activated to gamma-emitting 153 samarium before dosing. Serial blood samples were collected for analysis of avitriptan up to 24-hr postdose, and serial scintigraphic images were obtained to assess the plasma concentration–time profile in relation to the GI transit of the avitriptan capsule contents. Bioavailability of avitriptan was reduced when administered in the fed condition but only the decrease in AUC(INF) was statistically significant Tmax was significantly delayed between the fed conditions and the fasted condition. Qualitative appearance of plasma concentration–time profiles for avitriptan could be related to the manner in which the drug emptied from the stomach. It was also apparent that avitriptan exerted a secondary pharmacologic effect that temporarily suspended gastric emptying in the fasted treatment. Thus, when gastric emptying was interrupted and then resumed, the net result was a double peak in some of the individual plasma concentration profiles. Scintigraphic analysis also demonstrated that upon emptying from the stomach, avitriptan was rapidly absorbed from the upper small intestine. In the fed state, gastric emptying was slow and continuous resulting in extended absorption and a lower occurrence of double peaks. Qualitatively, the intrasubject variability in Cmax and AUC could be explained by the intrasubject variability in gastric emptying in both fasted and fed conditions.
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