Albumin-binding of diclofenac and the effect of a site II inhibitor in the aqueous humor of cataract patients with the instillation of diclofenac.

Diclofenac instillation has been used widely in cataract surgery to prevent postoperative inflammation. Since diclofenac binds strongly to albumin in the circulation, it does not have a sufficient effect on patients in whom diclofenac binds strongly to albumin in the aqueous humor. A decrease in diclofenac binding and an increase in free diclofenac levels are necessary in these patients. The binding of diclofenac to albumin was investigated in the aqueous humor. In a diclofenac binding assay with albumin in the aqueous humor of individual patients, diclofenac was extracted from aliquots of the aqueous humor, and its total levels were measured using ultra high performance liquid chromatography (UHPLC). Free diclofenac levels were measured using ultrafiltration and UHPLC. The albumin-binding fraction of diclofenac was 0.8 or higher in the aqueous humor of some patients. Ibuprofen significantly inhibited diclofenac binding to site II of albumin in mimic aqueous humor, but not in pooled aqueous humor. This difference may have been due to the weak binding of diclofenac to site II in the pooled aqueous humor. Flurbiprofen was used instead of diclofenac. Flurbiprofen has been shown to bind more strongly than diclofenac to the same site of albumin. Thus, the inhibitory effect of ibuprofen on the binding of flurbiprofen to albumin was investigated in pooled aqueous humor. The results indicated that ibuprofen significantly inhibited the flurbiprofen binding. An effective diclofenac administration method may be established for clinical application by the instillation of an appropriate inhibitor of binding to the albumin site II.

A diclofenac suppository-nabumetone combination therapy for arthritic pain relief and a monitoring method for the diclofenac binding capacity of HSA site II in rheumatoid arthritis.

Diclofenac suppository, a non-steroidal anti-inflammatory drug (NSAID), is used widely in rheumatoid arthritis (RA) patients with severe arthritic pain. As the binding percentage of diclofenac to serum proteins is high, its free (unbound) concentration after rectal administration is low. To increase temporarily the free concentration of diclofenac and to enhance its analgesic effect by inhibiting the protein binding of diclofenac, the analgesic effect of diclofenac was examined before and after the start of an inhibitor administration to RA patients with insufficient control of arthritic pain, and the protein binding capacity of diclofenac was evaluated. Binding experiments were performed by ultrafiltration, and arthritic pain was recorded by the face scale. Free fractions of diazepam and diclofenac were augmented by increasing 6-methoxy-2-naphthylacetic acid (6-MNA; the active metabolite of the NSAID nabumetone) concentrations. The free fraction of diazepam increased after the start of nabumetone administration to RA patients, and arthritic pain relief was observed. These results suggest that 6-MNA has an inhibitory effect on the protein binding of diclofenac and the free fraction of diazepam can be used to evaluate the binding capacity of diclofenac. It is considered that diclofenac suppository-nabumetone combination therapy and the method for protein binding monitoring by diazepam can positively benefit RA patients with insufficient control of arthritic pain.

Caffeine increases the antitumor effect of Cisplatin in human hepatocellular carcinoma cells.

Caffeine is thought to increase the antitumor effect of cisplatin or DNA-damaging agents because it is known that caffeine inhibits DNA repair. Caffeine-assisted chemotherapy has been used in the treatment of osteosarcomas. In addition, there are several reports about combination chemotherapy with caffeine for certain malignancies other than osteosarcomas. However, there are no reports that show the utility of combination chemotherapy with caffeine for hepatocellular carcinoma (HCC). We examined the combined effects of caffeine and cisplatin in human HCC cell lines, and screened for a more effective administration method of caffeine in vitro. Human HCC cell lines (HepG2, HLF, HuH-7, and Li-7) were exposed to caffeine (0-0.5 mM) and cisplatin (0-1.2 µg/mL) for 72 h, either alone or in combination. Cell numbers were measured by WST-8 assay, and cell apoptosis was determined by annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) binding assay. As a result, caffeine increased the antitumor effect of cisplatin on cell proliferation and cell apoptosis in the HCC cell lines. Moreover, this effect was dependent on the amount of exposure to caffeine. These results suggest that caffeine-assisted chemotherapy is useful for HCC treatment.

Hyuganatsu orange (Citrus tamurana Hort. Ex Tanaka) contains a water soluble substance that suppresses bone loss in ovariectomized rats.

We investigated whether Hyuganatsu orange (Citrus tamurana Hort. ex Tanaka) contains water and acetic-acid soluble substances that increase bone mineral density (BMD) in ovariectomized rats. In in vivo study, femoral BMD can significantly increased. In in vitro study, tartrate-resistant acid phosphatase (TRAP) positive cells significantly decreased. We speculate that Hyuganatsu orange contains biologically active substances other than hesperidin that increase BMD.

Hepatic fibrosis does not affect the pharmacokinetics of 5-fluorouracil in rats.

In the case of cancer chemotherapy for hepatocellular carcinoma, 5-fluorouracil (5-FU) is used widely, and has typically been given by intrahepatic arterial (i.a.) infusion to increase treatment efficacy and to reduce systemic toxicity. 5-Fluorouracil is eliminated primarily by the liver, and so its use in patients with hepatic disease can be difficult. This study investigated the effect of hepatic fibrosis on the pharmacokinetics of 5-FU in rats. Experimental hepatic fibrosis was induced by carbon tetrachloride treatment. 5-fluorouracil was infused for 15 min into the hepatic artery or the saphenous vein of the rats at a dose of 1.25 mg/kg. There were no significant differences in the plasma concentration and AUC of 5-FU between hepatic disease rats and their controls after both intravenous and intraarterial injection. This result is probably attributed to the fact that there were no significant differences in hepatic blood flow and dihydropyrimidine dehydrogenase (DPD; an initial and rate-limiting enzyme in 5-FU catabolism) activity between hepatic disease rats and their controls, because the total clearance of 5-FU after intravenous and intraarterial administration is mainly limited by hepatic blood flow and DPD activity, respectively. In conclusion, the pharmacokinetics of 5-FU is not affected by hepatic fibrosis, unlike that of many hepatically metabolized drugs.

Possible roles of intestinal P-glycoprotein and cytochrome P450 3A on the limited oral absorption of irinotecan.

OBJECTIVES: Irinotecan is a widely intravenously used drug for the treatment of certain types of solid tumours. The oral administration of irinotecan has recently been recognized as being a more effective method for the treatment than intravenous administration. However, the limited oral bioavailability of irinotecan poses a problem for its oral delivery. In this study, we report on an investigation of the mechanism responsible for the limited oral absorption of irinotecan using rats as models. METHODS: The intestinal absorption of irinotecan in the absence and presence of several compounds was examined using intestinal loop method. The pharmacokinetics of irinotecan was investigated when verapamil, an inhibitor of the P-glycoprotein (P-gp) and cytochrome P450 3A (CYP3A) was pre-administered. KEY FINDINGS: The intestinal absorption of irinotecan was enhanced in the presence of verapamil, indicating that efflux by intestinal P-gp contributes to its limited oral absorption. Indeed, the oral bioavailability of irinotecan was increased when verapamil was orally pre-administered. This increased oral bioavailability was accompanied by a slight but significant decrease in the formation of a metabolite produced by the action of CYP3A. CONCLUSION: The findings presented herein suggest that intestinal efflux by P-gp is mainly and intestinal metabolism by CYP3A is partially responsible for the limited oral absorption of irinotecan.

Tumor Growth Suppression With Novel Intra-arterial Chemotherapy Using Epirubicin-entrapped Water-in-oil-in-water Emulsion In Vivo.

BACKGROUND/AIM: A mixture of anticancer agents and iodized poppy seed oil (IPSO) has been widely used for intra-arterial chemotherapy of hepatocellular carcinoma. However, the anticancer agents can easily separate from IPSO, so the therapeutic potential is limited. We developed epirubicin-entrapped water-in-oil-in-water emulsion (WOW-Epi) using a double-membrane emulsification technique. MATERIALS AND METHODS: We delivered WOW-Epi through a hepatic arterial injection to VX2 hepatic tumor rabbit model (1.2 mg/kg). RESULTS: VX2 tumor growth was selectively suppressed in the WOW-Epi-treated group compared with the control treated groups. The accumulation of WOW in nearby cancer cells was confirmed via electron-microscopy. Endocytosis seemed to be the mechanism underlying the uptake of WOW. CONCLUSION: WOW-Epi led to tumour growth suppression in vivo. WOW does not cause toxicity to arterial vessels. WOW-Epi will be hopefully used for repeated intra-arterial chemotherapy to HCC patients in the near future.

Hepatocyte growth factor increases uptake of estradiol 17beta-D-glucuronide and Oatp1 protein level in rat hepatocytes.

Hepatocyte growth factor (HGF) ameliorates liver injuries in hepatectomized cholestatic rats. On the other hand, the protein level of organic anion-transporting polypeptide (Oatp1), which is responsible for the uptake of bile salts into hepatocytes, decreases in cholestatic humans and rats. However, the relationship between the ameliorative effects of HGF and the decrease in Oatp1 levels in cholestasis remains to be understood. Therefore, in order to investigate this relationship, we evaluated the effects of HGF on the function and protein level of Oatp1. HGF treatment significantly increased the uptake of radiolabeled estradiol 17beta-d-glucuronide ([(3)H]E(2)17betaG), a predominant Oatp1 substrate, in primary cultured rat hepatocytes. Additionally, there was an increase in the Oatp1 protein levels. The increased [(3)H]E(2)17betaG uptake was significantly inhibited by simultaneous incubation with the HGF receptor antibody and treatment with non-radiolabeled E(2)17betaG. However, inhibition by taurocholic acid, a Na(+)-taurocholate co-transporting polypeptide (Ntcp) substrate, was weaker than that caused by non-radiolabeled E(2)17betaG. Further, the increase was not altered by replacing Na(+) in the medium with Li(+). In the inhibition study, the increased [(3)H]E(2)17betaG uptake was inhibited by Oatp1 substrates, including bromosulfophthalein, ochratoxin A, and ouabain, but not by digoxin, which is an Oatp2-specific substrate. Furthermore, HGF did not alter the Oatp1 mRNA expression. In contrast, HGF treatment suppressed the ubiquitination of Oatp1 protein. In conclusion, this is the first report suggesting that HGF regulates Oatp1 protein level and that the ameliorative effects of HGF in cholestasis was induced, at least in part, by correcting the down-regulation of the Oatp1 protein level.

Inhibitory effects of fruit juices on cytochrome P450 2C9 activity in vitro.

There is limited information on the effect of fruits on human cytochrome P450 (CYP) 2C9 activity. The objective of this study was to determine the effect of fruit juice on CYP2C9-mediated drug metabolism. Nine citrus fruits and eight tropical fruits were chosen. We investigated effects of the fruits on diclofenac 4'-hydroxylation and tolbutamide hydroxylation by human liver microsomes. Among the fruits, pineapple juice showed potent inhibition of CYP2C9 activity. The addition of 25 microl (5.0% v/v) of pineapple juice resulted in almost complete inhibition. Next we examined the inhibitory effect of bromelain, a cysteine protease in pineapple. Bromelain also strongly inhibited CYP2C9 activity. In addition, E-64, a cysteine protease inhibitor, almost entirely blocked inhibition by pineapple juice and bromelain. Thus we found that pineapple juice was a potent inhibitor of CYP2C9, and that the inhibitory effect might be due to the bromelain contained in pineapple.

Dosage plan of a flurbiprofen injection product using inhibition of protein binding by lipid emulsion in rats.

Flurbiprofen-axetil (FP-ax), a bolus injection product of a non-steroidal anti-inflammatory drug (NSAID), is a prodrug of flurbiprofen, an NSAID. As flurbiprofen strongly binds to site II of human serum albumin (HSA), the free (unbound) concentration of flurbiprofen after injection of FP-ax is low. We have examined the inhibitory effect of free fatty acid (FFA), a binding inhibitor for site II of HSA, on the binding of flurbiprofen in-vitro and in-vivo by ultrafiltration, to establish an effective dosage of FP-ax. In-vitro, fatty acid mixtures (FAs) inhibited the binding of flurbiprofen to rat serum albumin. The free fraction of flurbiprofen was remarkably increased by FAs in rat serum. In-vivo, FP-ax was injected into a control group (low FFA concentration in serum) and a lipid emulsion group (high FFA concentration in serum). The area under the curve of the free concentration of flurbiprofen during the alpha phase and the distribution volume of the central compartment of flurbiprofen were significantly higher in the lipid emulsion group than the control group (5.0- and 1.2-times, respectively). When FP-ax was administered at high FFA concentration, the free concentration of flurbiprofen and distribution of flurbiprofen to tissues increased transiently. This administration method may be useful for patients with cancer pain, having a potent analgesic effect.

[Medical emergency education using emergency care simulators in the School of Pharmaceutical Sciences].

Clinical pharmacy training III (bedside training) in the School of Pharmaceutical Sciences, Kyushu University of Health and Welfare is intended to train pharmacists who can also cope with medical emergencies. Therefore we produced original scenarios that provide experience of various medical emergencies using emergency care simulators. As a result, these simulators enabled students to experience dealing with various medical emergencies such as cardiopulmonary resuscitation, automated external defibrillation (AED), adrenalin administration, and oxygen inhalation. In addition, a survey on the necessity for and the degree of the understanding of training contents associated with emergency care simulators was performed before and at the end of clinical training. After clinical training, the necessity for and the degree of the understanding of these training contents significantly increased (p<0.01). The introduction of emergency care simulators into clinical pharmacy training provides experience of not only cardiopulmonary resuscitation but also the treatment procedures as well as observation of improvement in the pathological condition after drug administration, which increases pharmacists' awareness of patient needs in drug therapy. Therefore these simulators are helpful for pharmacy education aiming at improving pharmacists' pharmaceutical care ability.

Relationship between UGT1A1*27 and UGT1A1*7 polymorphisms and irinotecan-related toxicities in patients with lung cancer.

BACKGROUND: The objective of this study was to evaluate the effects of gene polymorphisms, including UGT1A1*7, *27, and *29, on the safety of irinotecan therapy. METHODS: The eligibility criteria were: lung cancer patients scheduled to undergo irinotecan therapy, aged ≥ 20 years, with a performance status of 0-2. Thirty-one patients were enrolled and their blood was collected and used to examine the frequency of UGT1A1*6, *7, *27, *28, and *29 polymorphisms and the concentrations of irinotecan, SN-38, and SN-38G after irinotecan therapy. RESULTS: The patients' characteristics were as follows: male/female 25/6, median age 71 years (range 55-84), stage IIB/IIIA/IIIB/IV 2/6/11/12, and adenocarcinoma/squamous cell carcinoma/small cell carcinoma/other 14/10/3/4, respectively. The -/-, *6/-, *7/-, *27/-, *28/-, and *29/- UGT1A1 gene polymorphisms were observed in 10 (32%), 10 (32%), 2 (6%), 2 (6%), 7 (23%), and 0 (0%) cases, respectively. The UGT1A1*27 polymorphism occurred separately from the UGT1A1*28 polymorphism. The lowest leukocyte counts of the patients with the UGT1A1*27 and UGT1A1*6 gene polymorphisms were lower than those observed in the wild-type patients. SN-38 tended to remain in the blood for a prolonged period after the infusion of irinotecan in patients with UGT1A1*27 or UGT1A1*28 polymorphisms. No severe myelotoxicity was seen in the patients with UGT1A1*7. CONCLUSION: UGT1A1*27 can occur separately from UGT1A1*28 and is related to leukopenia during irinotecan treatment. UGT1A1*7 is less relevant to irinotecan-induced toxicities, and UGT1A1*29 seems to have little clinical impact.

Adsorption of irinotecan onto oral adsorbent AST-120 (Kremezin) for preventing delayed diarrhea.

PURPOSE: One of the significant dose-limiting toxicities of irinotecan hydrochloride (CPT-11) is severe diarrhea due to impairment of the intestinal membrane induced by the excreted CPT-11 and its metabolites. AST-120 (Kremezin) is a prominent oral adsorbent that consists of porous spherical carbonic particles. To evaluate whether Kremezin can prevent the diarrhea induced by CPT-11, we investigated the adsorption characteristics of CPT-11 and its metabolites onto Kremezin in vitro and in vivo. METHODS: For in vitro studies, Kremezin was added to each solution containing one of the camptothecin drugs (CPT-11, SN-38, and SN-38-glucuronide), and adsorption activities were determined under various conditions. For in vivo studies, CPT-11 was consecutively administered, and the occurrence of diarrhea was compared between Kremezin-treated and non-treated rats. RESULTS: Kremezin drastically adsorbed the camptothecin drugs in vitro, and the adsorption percentages of the camptothecin drugs for 60 min were more than 85%. In addition, the frequency of diarrhea in Kremezin-treated rats decreased by approximately half of that in the non-treated rats. CONCLUSION: Kremezin showed potent adsorption capacities for the camptothecin drugs and mitigated the symptoms of diarrhea in rats. These results suggest that Kremezin is useful to prevent the diarrhea in clinical CPT-11 chemotherapy.

[Interpretations of laboratory test data on serum protein binding].

Serum proteins that are important in the serum protein binding of drugs are human serum albumin (HSA) and alpha1-acid glycoprotein (AGP). Several binding sites exist on HSA and AGP molecules. HSA, AGP, free fatty acid (FFA), blood urea nitrogen (BUN) and bilirubin, which can all be determined by laboratory test, affect the binding capacities of binding sites on these proteins. The increase and decrease of HSA and AGP influence the binding capacities of all binding sites. As an additional influence on the binding sites on protein molecules, the increment of FFA decrease the binding capacity of site II, while binding capacity of site I is enhanced by FFA. Increase in bilirubin remarkably decreases the binding capacity of site I. BUN data are associated with the amounts of several uremic toxins, 3-carboxy-4-methyl-5-propyl-2-furanpropanate (CMPF), indole-3-acetate (IA), indoxyl sulfate (IS) and hippurate (HA). With CMPF, the binding capacity of site I is decreased, while IA, IS, HA contribute to the binding inhibition of site II of HSA. If we can monitor binding capacities of binding sites of HSA and AGP, laboratory test data can be interpreted from a pharmaceutical perspective regarding protein binding, because changes in laboratory test data that are endogenous substance concentrations have an influence on the binding capacities of those binding sites.

[Need for pharmaceutical skill in using displacement of protein binding].

In pharmacotherapy, to alleviate pains of patients and to provide comforts to patients, pharmacists should improve their pharmaceutical skills of their clinical sense involving pharmaceutical investigational outcomes. Without pharmaceutical skills, pharmacists cannot apply the essence of drug therapies for patients in the most urgent 24 hours treatment. To cope with these drug therapies, we have developed search methods which easily identify the diachronic change of protein binding and the factors in serum (=a new pharmaceutical distribution diagnostic method). This method can speculate diachronic change factors in serum, by monitoring diachronically binding capacities of drug binding sites on human serum albumin (HSA) and alpha(1)-acid glycoprotein (AGP) molecules in patient sera (add each site probe to each patient serum, and measure the free level of each probe by using TDX/FLX analyzer and HPLC detector), and considering the binding capacities and values of HSA, AGP, free fatty acids, bilirubin (Bil) and blood urea nitrogen (BUN) associating with the amounts of uremic toxins laboratory tests. In addition, the diagnostic method could attempt effective administration by using the protein binding displacement of drugs that have a high protein binding capacity and small distribution volume, or high targeting (=the pharmaceutical skill of protein binding displacement). We have practiced pain control of patients with rheumatoid arthritis by the pharmaceutical skill. It is important for pharmacists to master the pharmaceutical skill in pharmacotherapy.

Intestinal alkalization as a possible preventive mechanism in irinotecan (CPT-11)-induced diarrhea.

The therapeutic efficacy of irinotecan (CPT-11), a DNA topoisomerase inhibitor, is often limited by the induction of severe late-onset diarrhea. This prodrug and its active metabolite, 7-ethyl-10-hydroxy-camptothecin (SN-38), have a labile alpha-hydroxy-lactone ring that undergoes pH-dependent reversible hydrolysis. At physiological pH and higher, equilibrium favors the less toxic carboxylate form, whereas at acidic pH, the more potent lactone form is favored. We have reported previously that the initial uptake rate of CPT-11 and SN-38 by intestinal cells was significantly different between the respective lactone and carboxylate form. Results from the present study in HT-29 cells further demonstrate the correlation between the CPT-11/SN-38 initial uptake rate and the induced toxicity, cell cycle alteration, apoptosis, and colony-forming efficiency. The exposure of HT-29 cells to SN-38 for a limited period of time (<2 h) was sufficient to induce these events. Because the decreased initial uptake of SN-38 carboxylate resulted in a reduced cellular toxicity, we postulated that the CPT-11-induced diarrhea was preventable by influencing the equilibrium toward the carboxylate form and, thus, reducing its intestinal uptake. In the golden Syrian hamster model, p.o. sodium bicarbonate supplementation (5 mg/ml in drinking water) led to alkalization of the intestinal contents. In addition, this alkalization resulted in the reduction of the histopathological damage to the mucosa of the small and large intestine, as well as a 20% reduction of the intestinal SN-38 lactone concentration of animals receiving CPT-11 (20-50 mg/kg x 7 days). Taken together, these results from in vitro and in vivo studies support intestinal alkalization by sodium bicarbonate supplementation as a preventive mechanism against CPT-11-induced diarrhea. In addition, this provides a strong rationale for the usage of this measure as an adjunct to CPT-11 treatment.

Development of the Virtual Physical Assessment Learning Material That Allows the Learners to Check Drug Efficacy and Early Detection of Adverse Effects through Virtual Experience.

We utilized the information and communication technology to develop the physical assessment (PA) learning materials in the virtual experience type. This learning material consists of two parts which include case learning and basic learning. We created example scenarios about various conditions that a pharmacist may experience in medical scenes such as in a hospital ward, community pharmacy, home, and drugstore. Illustrations of a virtual patient's avatar before and after taking the medicines were incorporated in the learning materials. The virtual training includes a stethoscope that was used in examining sounds (heart, pulmonary and bowel sounds) that served as evidences in the confirmation of drug efficacy and its possible adverse effects. In addition, we included the images of each body part, the 24 format question items, the palpation (rate and rhythm) of the radial artery, brachial artery and pedal artery, the clinical data obtained from several medical equipment, the pupillary reflex, and the urine dipstick test. This way, learners are able to experience PA with reference to the subjective and objective data from patient reception and questions. The virtual patient's avatar displayed on the monitor features auscultatory sounds on the stethoscope. It also features clinical data obtained from other medical equipment that can give the learners an interactive way of learning about various medical conditions. For evaluation, we gave out questionnaires on the virtual PA to pharmacy students. As a result, a high evaluation was reflected in terms of the degree of usefulness for both case learning and basic learning.

Pramipexole reduces parkinsonian tremor induced by pilocarpine infusion in the rat striatum.

OBJECTIVE: Pramipexole is widely prescribed for the treatment of Parkinson's disease. This dopamine (DA) receptor agonist has a higher affinity for D3 over D2 receptors. We compared the effect of pramipexole to apomorphine, a non-specific DA receptor agonist, on the suppression of tremulous jaw movements (TJMs) in a rat model, to elucidate the possible ameliorating effect of D3 receptor activation on parkinsonian tremor. RESULTS: In experiment 1, pilocarpine (4.0mg/kg) was injected into rats intraperitoneally, and the number of rapid vertical deflections of the lower jaw was counted for 20min immediately after the injection, to evaluate TJMs. TJMs were reduced by intraperitoneal administration of pramipexole (1.0mg/kg). In experiment 2, the number of TJMs was counted after the rats received intraperitoneal administration of either apomorphine (0.25, 1.0, 4.0mg/kg) or vehicle, followed by the micro-infusion of pilocarpine (50µg/1µL/side) or vehicle into the ventrolateral striatum (VLS) via implanted guide cannulae. In experiment 3, either pramipexole (0.25, 1.0, 4.0mg/kg) or vehicle was intraperitoneally administered, followed by the micro-infusion of pilocarpine or vehicle into the VLS 30min later. Pramipexole (1.0 and 4.0mg/kg) and apomorphine (1.0 and 4.0mg/kg) significantly reduced the number of TJMs induced by micro-infusion of pilocarpine into the VLS. CONCLUSIONS: These findings suggest that activation of D3, as well as D2 receptors could play important roles in the suppression of parkinsonian tremor.

Hypoglycemic effect of surfactant-coated insulin solubilized in a novel solid-in-oil-in-water (S/O/W) emulsion.

A novel solid-in-oil-in-water (S/O/W) emulsion for oral administration of insulin has been developed using surfactant-coated insulin. The S/O/W emulsion prepared by a shirasu porous glass (SPG) membrane provided a sharp size distribution and was stable. Leakage of insulin from the S/O/W emulsions was not observed for several days. The S/O/W emulsion showed the hypoglycemic activity for a long period after oral administration to rats.

Prediction of plasma concentration-time curve of orally administered theophylline based on a scintigraphic monitoring of gastrointestinal transit in human volunteers.

The plasma concentration-time profile of theophylline after oral administration in human volunteers was predicted using the individual gastrointestinal (GI) transit data monitored by a gamma scintigraphic technique. Theophylline was administered as aminophylline under fasted and fed condition, along with 99mTc-labeled diethylenetriamine-pentaacetic acid (DTPA), an unabsorbable marker to evaluate the GI transit by a gamma scintigraphic technique. Two healthy male volunteers participated under fasted and fed conditions in a crossover study. The GI transit was evaluated by dividing the GI tract to four segments, stomach, jejunum, ileum and cecum/colon. Under the fed condition, the GI transit pattern for each segment was confirmed to alter considerably, causing a delay in the gastric emptying mainly. Further, the plasma concentration curves of theophylline after oral administration were predicted using the GI-Transit-Absorption Model on the basis of individual GI transit parameters calculated by the fitting of the observed data to the GI-Transit Kinetic Model. The absorption rate constant in each segment and the pharmacokinetic parameters after intravenous administration used for the prediction were the values extrapolated from the data in rats and the ones normalized from the values in literatures, respectively. The plasma concentration-time curves for theophylline were well predicted using obtained individual GI transit parameters. The analysis using this method could estimate the variable absorption behavior governed by the GI transit in detail.