Intra- and postoperative low-dose ketamine for adolescent idiopathic scoliosis surgery: a randomized controlled trial

BACKGROUND

In this randomized controlled trial, we examined whether intra- and postoperative infusion of low-dose ketamine decreased postoperative morphine requirement and morphine-related adverse effects as nausea and vomiting after scoliosis surgery.

METHODS

After IRB approval and informed consent, 36 patients, aged 10-19 years, undergoing posterior correction surgery for adolescent idiopathic scoliosis, were randomly allocated into two groups: intra- and postoperative ketamine infusion at a rate of 2 μg/kg/min until 48 h after surgery (ketamine group, n = 17) or infusion of an equal volume of saline (placebo group, n = 19). All patients were administered total intravenous anesthesia with propofol and remifentanil during surgery and intravenous morphine using a patient-controlled analgesia device after surgery. The primary outcome was cumulative morphine consumption in the initial 48 h after surgery. Pain scores (Numerical Rating Scale, NRS, 0-10), sedation scales, incidence of postoperative nausea and vomiting (PONV), and antiemetic consumption were recorded by nurses blinded to the study protocol for 48 h after surgery.

RESULTS

Patient characteristics did not differ between the two groups. Cumulative morphine consumption for 48 h after surgery was significantly lower in the ketamine group compared to the placebo group (0.89 ± 0.08 mg/kg vs. 1.16 ± 0.07 mg/kg, 95% confidence interval for difference between the means, 0.03-0.48 mg/kg, P = 0.019). NRS pain, sedation scales, and incidence of PONV did not differ between the two groups. Antiemetic consumption was significantly smaller in ketamine group.

CONCLUSIONS

Intra- and postoperative infusion of low-dose ketamine reduced cumulative morphine consumption and antiemetic requirement for 48 h after surgery.

Turn-over orbital septal flap and levator recession for upper-eyelid retraction secondary to thyroid eye disease

BACKGROUND

A turn-over septal flap has been reported as a spacer for levator lengthening in a single case report. This study reports the preliminary outcomes of this technique in a series of patients with upper-lid retraction (ULR) associated with thyroid eye disease (TED) causing symptomatic exposure keratopathy (EK).

METHODS

Retrospective, multicenter study of 12 eyelids of 10 patients with TED undergoing a transcutaneous levator-lengthening technique using the reflected orbital septum (OS) as a spacer. Change in palpebral aperture (PA) and contour, position of the skin crease (SC), symptoms of EK, and complications were recorded.

RESULTS

The average age was 47.5 years. Two patients were excluded, as their septa were found to be very thin at surgery. At an average of 13 months postoperatively, the PA was reduced by 2.5 mm on average (P<0.001) and was within 1 mm of the contralateral eyelid in 11 cases (92%); the position of the SC was within 1 mm of the desired position in all cases. EK resolved in all cases. Complications included one case of overcorrection and one case of recurrent lateral flare.

CONCLUSIONS

The turn-over orbital septal flap technique may be a viable option as an autogenous spacer for the treatment of ULR in TED. This technique may be possible in cases where the OS has been opened by previous surgery but may not be feasible in patients in whom the septum is very thin.

Genome-wide association scan detected candidate polymorphisms associated with overall survival (OS) in advanced non-small cell lung cancer (NSCLC) treated with carboplatin (CBDCA) and paclitaxel (PTX)

8031

Background: The combination of CBDCA and PTX is one of the standard chemotherapy for patients with advanced NSCLC. Genome-wide association studies (GWAS) are a powerful tool for identifying genes for biomarkers of common diseases. This prospective study was investigated whether candidate polymorphisms in GWAS could influence OS in advanced NSCLC patients treated with CBDCA and PTX. Methods: Chemotherapy naïve stage IIIB or IV NSCLC patients, treated with CBDCA (AUC=6mg/ml/min) and PTX (200mg/m2, 3-hour), were eligible in this study. The DNA samples were extracted from peripheral blood mononuclear cells before treatment and 110,000 SNPs were obtained by Illuimna's Sentrix Human-1 Genotyping BeadChip. Statistical analyses were performed by the log-rank test and Cox proportional hazards model in consideration of the linkage disequilibrium. Results: From July 2002 to May 2004, 117 patients (male/female: 85/32, PS 0/1/2: 22/92/3, stage IIIB/IV: 50/67), aged 29–80 (median: 61) years, received a total of 387 cycles of treatment. The median survival time (MST) of 117 patients was 17.1 months. In the GWAS, four SNPs were associated significantly with shortened OS: rs1656402 in the EIF4E2 Gene (MST for AG [n = 54] + AA [n = 44] and GG [n = 19] were 18.2 and 7.7 months, respectively; p = 4.2× 10-7, HR = 3.58 [2.1–6.1]), rs1209950 in the ETS2 gene (MST for AA [n = 105] and AG [n = 12] + GG [n = 0] were 17.7 and 7.0 months, respectively. p = 9.2×10-8, HR = 4.95 [2.6–9.5]), rs10074374 (MST for CC [n = 114] and CT [n = 3] + TT [n = 0] were 17.1 and 2.2 months, respectively. p = 2.2×10-6, HR = 23.2 [6.3–85.1]) and rs2063681 (MST for CT [n = 45] + CC [n = 61] and TT [n = 11] were 17.8 and 6.6 months, respectively. p = 5.2×10-8, HR = 5.47 [2.8–10.9]). These four SNPs were statistically significant even after multiple comparison adjustment. Conclusions: GWAS is a powerful tool to search for new prognostic biomarkers for patients with stage IIIB or IV NSCLC who receive CBDCA and PTX as the first-line chemotherapy and may unveil an unexplored molecular pathways correlated with the drug response.

[Table: see text]

The effects of vasoactive agents, platelet agonists and anticoagulation on thrombelastography

BACKGROUND

Platelet activation is a critical step in primary hemostasis and clot formation. We tested a hypothesis that platelet stimulating effects of vasoactive agents or platelet agonists could be shown using thrombelastography (TEG) as faster onset or increased clot strength. We further examined if TEG could be modified to evaluate activated platelets as a reversal of anticoagulation in the presence of partial thrombin inhibition.

METHODS

Blood samples were obtained from 126 non-cardiac surgical patients. Effects of vasoactive agents on TEG and aggregometry were examined using epinephrine, norepinephrine, vasopressin, desmopressin acetate, milrinone and olprinone (Experiment I). Platelet agonists (epinephrine, ADP and collagen) were separately tested on TEG (Experiment II). Effects of platelet agonists (ADP and collagen) on TEG under anticoagulation in the absence or presence of abciximab were studied (Experiment III). We also tested antiplatelet effects of milrinone and olprinone in the presence of anticoagulants on TEG (Experiment IV).

RESULTS

Neither vasoactive agents nor platelet agonists affected TEG or aggregometry results except for milrinone and olprinone on aggregometry (Experiment I, II). Platelet agonists facilitated clotting in the presence of anticoagulants (Experiment III). Abciximab-treated platelets still exhibited procoagulant effects in the presence of heparin, while not in the presence of argatroban (Experiment III). Platelet inhibition on the modified TEG was more extensive with milrinone than olprinone, and it was dose dependent (Experiment IV).

CONCLUSION

Modified TEG using heparin or argatroban might delineate the procoagulant effects of platelets by adding platelet specific agonist.

Genetic variations and haplotype structures of the ABCB1 gene in a Japanese population: an expanded haplotype block covering the distal promoter region, and associated ethnic differences

As functional ABCB1 haplotypes were recently reported in the promoter region of the gene, we resequenced the ABCB1 distal promoter region, along with other regions (the enhancer and proximal promoter regions, and all 28 exons), in a total of 533 Japanese subjects. Linkage disequilibrium (LD) analysis based on 92 genetic variations revealed 4 LD blocks with the same make up as previously described (Blocks -1, 1, 2 and 3), except that Block 1 was expanded to include the distal promoter region, and that a new linkage between polymorphisms -1,789G>A in the distal promoter region and IVS5 + 123A>G in intron 5 was identified. We re-assigned Block 1 haplotypes, and added novel haplotypes to the other 3 blocks. The reported promoter haplotypes were further classified into several types according to tagging variations within Block 1 coding or intronic regions. Our current data reconfirm the haplotype profiles of the other three blocks, add more detailed information on functionally-important haplotypes in Block 1 and 2 in the Japanese population, and identified differences in haplotype profiles between ethnic groups. Our updated analysis of ABCB1 haplotype blocks will assist pharmacogenetic and disease-association studies carried out using Asian subjects.

In vitro effects of antihypertensive drugs on thromboxane agonist (U46619)-induced vasoconstriction in human internal mammary artery

BACKGROUND

Hypertension is a major problem in the perioperative period of cardiac and non-cardiac surgery. The vascular endothelium plays a crucial role in modulating vascular tone by producing vasodilators as well as vasoconstrictors. Thromboxane A2 (TxA2), a prototypical vasoconstrictor produced by endothelium and platelets, may play an important role in the pathogenesis of hypertension and subsequent ischaemic events. Although multiple drugs are currently available to treat perioperative hypertension, there is a paucity of data comparing these agents. Therefore, we examined the in vitro vascular effects of commonly used antihypertensive drugs on human internal mammary artery (IMA) segments.

METHODS

Relaxation responses to adenosine (a nucleoside), enalaprilat (a competitive inhibitor of angiotensin-converting enzyme), fenoldopam (a D1-dopamine receptor agonist), hydralazine, labetalol (an alpha- and beta-adrenergic blocker), nicardipine (a calcium channel blocker), nicorandil (K(+)-ATP channel opener), nitroglycerin (GTN, a nitrosovasodilator), and sodium nitroprusside (SNP, a nitrosovasodilator) were studied in IMA segments pre-contracted with the TxA2 analogue (U46619, 1.0 x 10(-8) M). Effects of labetalol were also studied in IMA segments pre-contracted with norepinephrine (1.0 x 10(-6) M). All drugs were added in a cumulative fashion (range 10(-10) to 10(-3) M).

RESULTS

All agents in the current study, with the exception of enalaprilat, dilated the IMA segments pre-contracted with U46619. Only GTN and SNP induced a complete (90-100%) relaxation. The order of efficacy of the in vitro relaxation was as follows: SNP, GTN, nicardipine, nicorandil, fenoldopam, hydralazine, adenosine, and labetalol. The potency was in the order of GTN, SNP, fenoldopam, nicorandil, hydralazine, adenosine, and nicardipine.

CONCLUSIONS

Various antihypertensive agents are effective in attenuating U46619-induced IMA vasoconstriction, but the efficacy and potency differ. The in vitro vasodilation may not be simply extrapolated to the clinical efficacy or outcome of each antihypertensive therapy; however, our data provide additional grounds for the choice of antihypertensive medication. Further clinical studies are needed to help to fully elucidate the use of different antihypertensive agents and clinical outcomes.

Effects of tirofiban on haemostatic activation in vitro

BACKGROUND

Thrombin plays a critical role in normal haemostasis and pathological thrombosis. Heparin has long been a mainstay choice of antithrombotic regimen in cardiac patients, but persistent thrombin generation seems to occur during heparin therapy. Because platelets are integral to primary haemostasis and clot formation, we evaluated the use of tirofiban (Aggrastat),a platelet inhibitor, as a therapy to improve heparin sensitivity and delay thrombin formation.

METHODS

Blood samples were obtained from healthy subjects (n=8) and cardiac surgical patients (n=34). Thrombin formation was measured in platelet-rich plasma with a Thrombogram-Ascent fluorescent plate reader system. Platelet inhibition by tirofiban was evaluated with Plateletworks, and the interaction of tirofiban and heparin (>1.5 U ml(-1)) on clot formation was evaluated with Sonoclot Analyzer or kaolin activated clotting times (ACTs).

RESULTS

Addition of tirofiban (70-280 ng ml(-1)) progressively delayed onset of thrombin generation triggered by adenosine diphosphate (ADP). Plateletworks showed platelet inhibition with tirofiban (>35 ng ml(-1)), whereas heparin per se failed to produce platelet inhibition at 7 U ml(-1). Heparin (1.5 U ml(-1)) slowed the onset and rate of fibrin formation on Sonoclot analyses, and this was further slowed after addition of tirofiban (70 ng ml(-1)) to heparin-containing blood samples. Significant increases in ACT at all heparin concentrations were observed with the addition of tirofiban (70 ng ml(-1)). The addition of antithrombin (0.2 units/ml) to heparinized blood samples further prolonged ACTs, but the difference was not statistically significant when compared with heparin alone.

CONCLUSION

Tirofiban delays platelet activation-mediated thrombin generation and prolongs ACT in heparinized blood.

Hydrodynamic flows around tablets in different pharmacopeial dissolution tests

We investigated the hydrodynamic flows around tablets during several pharmacopeial dissolution tests: the rotating basket (RB), paddle (PD), flow-through cell (FT), and disintegration (DI) tests. The determination of hydrodynamic flow was based on the dissolution rate of United States Pharmacopeial salicylic acid nondisintegrating calibrators, and showed that, compared with the PD and RB methods, the FT method produced a lower hydrodynamic flow value whereas the DI method produced a higher value. The hydrodynamic flows during the PD and RB tests appeared to be similar at the same rotational speed, although the flow patterns around the tablet differed; with the RB method, homogeneous dissolution occurred from all surfaces of the tablet, while with the PD method, dissolution from the lower surface was slower. The use of a sinker seemed to enhance dissolution from the lower surface. Such differences in hydrodynamic flow could explain the apparently different dissolution behaviors of disintegrating prednisone and nondisintegrating acetaminophen tablets when assessed by the PD and RB methods. These differences in hydrodynamic flow between in vitro tests should be considered when choosing dissolution tests for studying in vitro/in vivo relationships and for quality control purposes.

Non-synonymous single nucleotide alterations found in the CYP2C8 gene result in reduced in vitro paclitaxel metabolism

By sequencing genomic DNA from 73 established cell lines derived from Japanese individuals, we detected 9 single nucleotide polymorphisms (SNPs) in the CYP2C8 gene. Of them, 3 exonic SNPs resulted in amino acid alterations (g416a, R139K; a1196g, K399R; c1210g, P404A). The first two alterations were detected concurrently in one cell line and thought to be the same as CYP2C8*3. To examine the effects of these amino acid alterations on CYP2C8 function, wild-type and four types of variant CYP2C8 cDNA constructs (R139K, K399R, R139K/K399R and P404A) were transfected into Hep G2 cells and their paclitaxel 6a-hydroxylase activities were determined in vitro. Km values were not significantly different from that of the wild-type in any of the variants studied. The variant R139K/K399R showed reduced values for Vmax and clearance (Vmax/Km) similar to those of its single variant, R139K. The variant P404A also showed a significantly lowered clearance due to reduced level of protein expression. These results suggest that not only the double variant (R139K/K399R, CYP2C8*3) but also our novel variant P404A in the CYP2C8 gene are less efficient in paclitaxel metabolism.

The study of the applicability of content uniformity and weight variation test--the state of commercial tablets and capsules in Japan

This study intends to determine the rational criteria (e.g., threshold value) for applying the weight variation test and to investigate the adequacy of the acceptance value for existing commercial products in Japan. The studied products were 489 lots (3 lots x 163 products) of compressed tablets (plain, film-coated, sugar-coated) and 42 lots (3 lots x 14 products) of hard capsules marketed in Japan. The individual drug content and the weight of 10 units in a lot were determined for each product and the acceptance values were calculated according to the Japanese Pharmacopoeia thirteenth edition (JP13) Content Uniformity Test (M=100.0, k=2.2). Product-specific intra-lot relative standard deviation of content (RSDD), weight (RSDW) and concentration (RSDC) were calculated by analysis of variance (ANOVA) using three lots of data per product. The RSDD and RSDC tended to increase with the decrease of the label strength for plain tablets, but not for film-coated and sugar-coated tablets, and hard capsules. A good correlation was found between RSDD and RSDC but not between RSDD and RSDW. These findings indicate that 1) it is difficult to rationally set the threshold level for weight variation, especially regarding the dosage forms except for plain tablets, 2) the application of weight variation tests should, in principle, be decided on the mixing homogeneity that is RSDC. 3) Most (99.6%) of the tablets and all the capsules investigated met the requirement of content uniformity test of JP13. Therefore the criteria of the JP13 content uniformity test are considered acceptable from the viewpoint of manufacturing capability.

Xeroderma pigmentosum variant heterozygotes show reduced levels of recovery of replicative DNA synthesis in the presence of caffeine after ultraviolet irradiation

Patients with xeroderma pigmentosum variant show clinical photosensitivity, skin neoplasias induced by ultraviolet light, and defective postreplication repair, but normal nucleotide excision repair. We recently reported an alternative, simple method for the diagnosis of xeroderma pigmentosum variant that measures by autoradiography three cellular markers for DNA repair after ultraviolet irradiation: unscheduled DNA synthesis, recovery of RNA synthesis, and recovery of replicative DNA synthesis. Among hereditary photosensitive disorders, including other xeroderma pigmentosum groups, Cockayne syndrome, and a newly established ultraviolet-sensitive syndrome, only xeroderma pigmentosum variant cells exhibited normal unscheduled DNA synthesis, normal recovery of RNA synthesis, but reduced recovery of replicative DNA synthesis (51 +/- 6% the rate relative to normal controls). This reduction of recovery of replicative DNA synthesis was enhanced in the presence of a nontoxic level of caffeine to 36 +/- 5%. In this study we assess the cellular markers in two independent families that included two photosensitive patients that were identified as xeroderma pigmentosum variant. Cells from heterozygotic parents showed normal levels of unscheduled DNA synthesis, recovery of RNA synthesis, and recovery of replicative DNA synthesis, but reduced rates of recovery of replicative DNA synthesis in the presence of 1 mM caffeine (53 +/- 8% relative to the normal control). Furthermore, with a colony-forming assay, the cells showed normal survival by ultraviolet without caffeine, but slightly reduced survival by ultraviolet with 1 mM caffeine present. In one family, we confirmed inheritance of two heterozygous mis-sense mutations. One mutation is an A-->G transition at nucleotide 1840 that generates a K535E mis-sense mutation. Another mutation is an A-->C transversion at nucleotide 2003 that generates a K589 mis-sense mutation. Each of these mutations were absent in 52 unrelated Japanese individuals. These results suggest that xeroderma pigmentosum variant heterozygotes can be identified by their sensitivity to ultraviolet irradiation in the presence of nontoxic levels of caffeine.

Hemodynamic effects of milrinone during weaning from cardiopulmonary bypass: comparison of patients with a low and high prebypass cardiac index

OBJECTIVE

To compare the hemodynamic effects of milrinone during weaning from cardiopulmonary bypass (CPB) in patients with a low pre-CPB cardiac index (CI) <2.5 L/min/m2) and in patients with a high pre-CPB CI (> or =2.5 L/min/m2).

DESIGN

Prospective, randomized, double-blind study.

SETTING

University hospital.

PARTICIPANTS

Forty-eight patients scheduled for elective coronary artery bypass graft surgery.

INTERVENTION

Patients were divided into 4 groups: (1) low pre-CPB CI/placebo, (2) low pre-CPB CI/milrinone, (3) high pre-CPB CI/placebo, and (4) high pre-CPB CI/milrinone. Patients received a loading dose of 20 microg/kg of milrinone followed by an infusion of 0.2 microg/kg/min or placebo 15 minutes before the anticipated weaning time.

MEASUREMENTS AND MAIN RESULTS

In the low pre-CPB CI/ placebo group, low CIs and high systemic vascular resistances (SVRs) were observed after CPB. High doses of dopamine and dobutamine were needed, and infusion of epinephrine was used in 5 of the 12 patients for hemodynamic support. Milrinone improved CI and reduced SVR in the low pre-CPB CI/milrinone group. Norepinephrine was needed to maintain an adequate systemic blood pressure in 6 of the 12 patients, however. In the high pre-CPB CI/placebo group, satisfactory CIs and SVRs were observed during weaning from CPB with low doses of dopamine and dobutamine. Milrinone significantly increased CI and decreased SVR in the high pre-CPB CI/milrinone group: 10 of the 12 patients had CIs above the upper limit of normal, and 7 patients had SVRs below the lower limit of normal.

CONCLUSION

Milrinone was effective during weaning from CPB in patients with a low pre-CPB CI. Milrinone in combination with norepinephrine was a good alternative to epinephrine for the treatment of myocardial dysfunction after CPB.

[Validation of dissolution testing: evaluation of vibration levels of dissolution apparatuses]

The collaborative study participated by seven laboratories was carried out to develop a dissolution standard for evaluating vibration levels of dissolution apparatuses using enteric-coated granules of cefalexin (EG). Dissolution apparatuses could be divided into two groups according to their vibration levels and the dissolution test results of EG by the rotating basket method at 50 rpm. The critical value of acceleration was about 0.05 m/s2. The upper limit of normal dissolution rates of EG was calculated from the results of the rotating basket method at 50 rpm obtained from low vibration apparatuses. All high vibration apparatuses used in this study were distinguished by the limit from low vibration apparatuses, although most of them were not distinguished by current USP calibrators. These results suggest that EG would be useful as a calibrator for detection of apparatuses on high vibration levels.

[Exceptional Application of Content Uniformity Test and Weight Variation Test in the Japanese Pharmacopoeia 13 revision and usage of these tests for in-process tests]

The criteria of Content Uniformity test and Weight Variation test in JP 13 were greatly changed to reduce consumer's risk. The new criteria were set to keep the rate of defectives in lots passing the tests less than the acceptable rate. However, in some cases, the new criteria can not directly be applied to some formulations and several modifications are needed in the criteria. In this report, the several resolution of this problem are represented. The applicability of these tests for in-process tests is also discussed.

Effects of codeine on the agitating force and gastrointestinal transit time in dogs, for use in drug absorption studies

Drug absorption studies using dogs have been difficult because of different gastrointestinal(GI) conditions between dogs and humans, including dogs' shorter intestinal transit time and strong agitation force in the GI tract. We attempted to modify the agitation force and GI transit time in dogs using codeine. The agitation force was examined based on the in vitro/in vivo correlation for a CR tablet of acetaminophen showing agitation-dependent release. Codeine improved the GI condition better than atropine or loperamide, employed previously.

Effects of atropine and loperamide on the agitating force and GI transit time in dogs in drug absorption studies

There are difficulties in drug absorption studies using dogs because of different gastrointestinal (GI) conditions between these animals and humans, including shorter intestinal transit time and strong agitation force in the GI tract. We attempted to modify the agitation force and GI transit time using atropine and loperamide. The agitation force was examined based on in vitro/in vivo correlation for two controlled release (CR) formulations of acetaminophen. Atropine treatment considerably reduced the agitating force whereas that of loperamide did not.

Effect of destruction force on drug release from multiple unit controlled release dosage forms in humans

PURPOSE

This study examined the effects of mechanical destructive forces on drug release from controlled release (CR) multiple unit dosage forms in vitro and in vivo and their colonic release, using two CR granules of acetaminophen, AG and BG, which differed in hardness (AG was hard and BG was soft), but which did not depend on agitation speed or pH for their release.

METHODS

In vitro release rates were determined using several official methods and the rotating dialysis cell method. Granules were administered to healthy volunteers under fasting and fed conditions.

RESULTS

Both granules showed similar release rates under mild destructive conditions in official dissolution tests, but BG showed a faster release rate in the rotating dialysis cell method. In the fasting state, the drug absorption-time profiles of AG and BG were almost equal. In the fed state, the drug release rate of BG increases whereas that of AG is almost equal to the fasted state. The food effect on BG could be caused by an increase in the mechanical stress of the GI tract due to food intake judging from the findings in vitro and in dogs. The colonic release from multiple unit CR products was larger than that from single unit ones.

CONCLUSIONS

In vivo release of drug from a multiple unit CR product that is structurally weak is affected by mechanical stresses, which differ among human subjects but are increased by food ingestion. Colonic release from multiple unit CR products is larger than that from single unit products.

Oral solid controlled release dosage forms: role of GI-mechanical destructive forces and colonic release in drug absorption under fasted and fed conditions in humans

PURPOSE

This study was undertaken to examine the effects of mechanical destructive forces on drug release from controlled release (CR) dosage forms in vitro and in vivo and their colonic release, using two CR tablets of acetaminophen A and B, showing slower and faster erosion rates, respectively.

METHODS

In vitro release rates were determined by several official methods. Tablets were administered to healthy volunteers under fasting and fed conditions.

RESULTS

Both tablets showed similar release rates under mild destructive conditions (e.g., paddle method at 10 rpm) but CR-B showed faster release under highly destructive conditions (e.g., rotating basket method at 150 rpm), where the tablet was eroded. The in vivo release from CR-B was faster than from CR-A, possibly because of enhanced erosion. The variable in vivo release from CR-B indicated large inter-subject differences in destructive GI forces. The fastest in vivo release from CR-B among individuals was approximated by the in vitro dissolution determined by destructive methods such as the rotating basket at 150 rpm. The slowest in vivo release from tablets A and B was lower than the dissolution by the paddle method at 10 rpm. The release from both tablets was markedly reduced at 3-4 hrs after dosing irrespective of feeding conditions which can be attributed to release inhibition in the colon.

CONCLUSIONS

Effects of GI destructive forces on the tablet erosion and the release inhibition in the colon must be considered in the development of CR dosage forms.

Estimation of agitation intensity in the GI tract in humans and dogs based on in vitro/in vivo correlation

In this study, we assessed the hydrodynamic flow around a dosage form in the GI tract in humans by comparing the characteristics of in vitro and in vivo release of two different types of controlled release acetaminophen (paracetamol) tablets, A and B. The former tablet showed an agitation speed-dependent release at a high speed range (50-100 rpm), whereas the latter showed this characteristic at a low speed range (10-50 rpm). The mean release amount-time profiles of tablets A and B in humans showed biphasic characteristics, and the first phase of the absorption profiles of A and B was close to their in vitro profiles at a paddle speed of 10 rpm. The in vivo profiles were also superimposable on in vitro dissolution curves obtained by the flow-through cell method at a flow rate of 1 mL/min (velocity 0.89 cm/min) or less. These results indicate that the hydrodynamic flow around the dosage forms in the human GI tract could be extremely low. The in vivo release rate of these tablets in dogs was greater than in humans, and was estimated to be equivalent to the release rate determined by the paddle method at 100 rpm. This indicates that a higher agitation intensity in the GI tract in dogs than in humans may be one cause of the discrepancies between humans and dogs in drug absorption studies.

In vitro and in vivo correlation for controlled-release formulation of d-chlorpheniramine maleate

Four commercial controlled-release tablets of d-chlorpheniramine maleate, which showed various drug release properties, were administered to beagle dogs, and the correlation between in vitro drug release and in vivo absorption was studied. The mean in vivo absorption amount-time profile for each product showed good accordance with the in vitro drug release profile until 2-3 h after administration. However, absorption of the drug in dogs terminated at about 3 h. This short absorption time may be due to a short intestinal residence time for these dosage forms in the dog. In the present study, the deconvolution method was proved to be useful for in vitro/in vivo comparison, which clarified the in vivo absorption of controlled-release dosage forms having various release profiles.