Mamoru Kobayashi

Effect of Switching Therapy to Pegaptanib in Eyes With the Persistent Cases of Exudative Age-Related Macular Degeneration

AbstractPurpose of this study was to evaluate the efficacy of switching to pegaptanib monotherapy for persistent cases of exudative age-related macular degeneration (AMD).Out of 296 eyes of 296 patients treated with ranibizumab or ranibizumab combined with photodynamic therapy (PDT), 50 eyes of 50 AMD patients were found to be resistant to these treatments. Over a 12-month period, intravitreal pegaptanib (IVP) 0.3 mg was administered at intervals of 6 weeks until the exudation disappeared prospectively. All patients were examined with the following tests: best-corrected visual acuity (BCVA) and central retinal thickness (CRT), determined at the initial visit, before the first IVP (baseline), and at 12 months. The factors responsible for achieving dry macula with IVP were examined statistically.The rate of persistent cases with intravitreal ranibizumab (IVR) and/or PDT was 17.0%. The mean number of IVPs administered was 5.4 (range, 2–9). Logarithm of the minimal angle of resolution BCVA at 12 months was stable or improved by ≥0.3 in 49 eyes (98.0%), with a significant improvement noted between the baseline and final BCVA (P = 0.01, paired t test). The CRT (mean ± standard deviation) was 446.9 ± 150.6 µm at the initial visit, 414.5 ± 146.5 µm at baseline, and 318.7 ± 99.0 µm at 12 months. There was a significant decrease in the mean CRT between the measurements at baseline and at 12 months after the first IVP (P = 0.002, Bonferroni correction). At 12 months, the exudative change was completely resolved in 27 eyes (54.0%) and reduced in 21 eyes (42.0%). The number of previous IVR treatments was significantly correlated with dry macula at 12 months.After switching therapy to pegaptanib in persistent cases of AMD, most patients maintained or improved their BCVA and exhibited a positive treatment response at 12 months.

The effect of vitreomacular and cataract surgery on oxygen saturation in retinal vessels

Purpose To evaluate the effects of vitreomacular and cataract surgery on retinal oximetry in vitreomacular disease. Patients and methods Thirty-eight eyes with epiretinal membrane (ERM) and 15 with idiopathic macular hole (MH) underwent 25 gauge pars plana vitrectomy combined with cataract surgery and intraocular lens implantation. Retinal oximetry was performed using the Oxymap T1 before, 1 month, and 6 months after surgery. Oxymap T1 simultaneously captures monochrome images of the fundus at two different wavelengths of light. Built-in Oxymap Analyzer software measures the oxygen saturation and vessel diameter. Results Mean arterial oxygen saturation significantly increased from 96.8%±6.2% to 100.2%±5.8% at 1 month and to 99.6%±5.8% at 6 months after surgery (P<0.01). Mean venous oxygen saturation also significantly increased from 54.6%±7.5% to 61.2%±6.4% at 1 month and to 62.6%±5.9% at 6 months after surgery (P<0.01). Mean arteriovenous (A-V) difference decreased from 42.2%±6.6% to 39.0%±7.8% at 1 month and to 37.0%±6.9% at 6 months after surgery (P<0.01). The ERM and MH groups showed similar changes in retinal oxygen saturation. However, there were no significant changes in the caliber of major retinal vessels after surgery (from 125.2±15.2 μm to 124.0±15.4 μm in artery, from 168.7±14.6 μm to 169.8±14.6 μm in vein). Conclusion Oxymap T1 was able to measure the increase in oxygen saturation in retinal arteries and veins, which led to a decrease in the A-V difference in oxygen saturation after vitrectomy combined with cataract surgery.

Development and validation of an LC–MS/MS method for simultaneously determining doxapram and keto-doxapram in human serum

AIM Doxapram, a respiratory stimulant, is used to treat apnea. A reliable method of determining doxapram in blood is required for monitoring purposes. RESULTS Doxapram, keto-doxapram (active metabolite) and propranolol (internal standard) were extracted from human serum by protein precipitation and plate filtration. Molecular ions were generated by electrospray ionization in positive ion mode, and the ions were analyzed using a triple-quadrupole mass spectrometer. The calibration curves were linear from 20 to 5000 ng/ml. The method was validated and the selectivity, reproducibility and stability met the acceptance criteria. CONCLUSION An LC-MS/MS method was successfully developed for determining doxapram and keto-doxapram in human serum. The method can be used to monitor doxapram and keto-doxapram concentrations in blood.

Absorption, disposition, metabolism and excretion of [14C]mizagliflozin, a novel selective SGLT1 inhibitor, in rats

Abstract The pharmacokinetic and metabolite profiles of mizagliflozin, a novel selective sodium glucose co-transporter 1 inhibitor designed to act only in the intestine, were investigated in rats. Mizagliflozin administrated intravenously (0.3 mg/kg) and orally (3 mg/kg) declined with a short half-life (0.23 and 1.14 h, respectively). The absolute bioavailability was only 0.02%. Following intravenous administration of [14 C]mizagliflozin (0.3 mg/kg), radioactivity in plasma was also rapidly declined. Up to 24 h after oral administration of [14 C]mizagliflozin (1 mg/kg), radioactivity was recovered in the faeces (98.4%) and in the urine (0.8%). No remarkable accumulation of radioactivity in tissues was observed using tissue dissection technique and whole body autoradiography. Orally dosed [14 C]mizagliflozin was mostly metabolised to its aglycone, KP232, in the intestine. In the plasma, KP232 and its glucuronide were predominant. KP232 glucuronide was also prominent in the bile and was recovered as KP232 in the faeces possibly because of the deconjugation by gut microflora. Mizagliflozin was observed neither in the urine nor the faeces. These findings suggest that orally administered mizagliflozin is poorly absorbed, contributing to low systemic exposure; if absorbed, mizagliflozin is rapidly cleared from circulation.

CLINICAL FEATURES OF TREATED AND UNTREATED TYPE 1 IDIOPATHIC MACULAR TELANGIECTASIA WITHOUT THE OCCURRENCE OF SECONDARY CHOROIDAL NEOVASCULARIZATION FOLLOWED FOR 2 YEARS IN JAPANESE PATIENTS

Purpose: To evaluate the clinical features of Type 1 idiopathic macular telangiectasia (IMT) followed up for 2 years. Methods: Forty-nine patients with unilateral Type 1 IMT were examined. Thirty-one IMT eyes were treated with direct laser photocoagulation and/or intravitreal bevacizumab; the remaining 18 eyes, with good vision or slight macular edema, were untreated. Changes in best-corrected visual acuity and central retinal thickness between baseline and 24 months after the initial visit were examined. Results: Of 49 eyes, nine were treated with direct laser photocoagulation, 12 with laser photocoagulation and intravitreal bevacizumab, 10 with intravitreal bevacizumab monotherapy, whereas 18 did not receive any treatment. The mean logarithm of the minimum angle of resolution best-corrected visual acuity was 0.20 ± 0.19 (median, 20/29) and 0.13 ± 0.22 (median, 20/25) at baseline and 24 months, respectively (P = 0.023). The mean central retinal thickness was 375.0 ± 94.5 &mgr;m and 315.3 ± 78.5 &mgr;m at baseline and 24 months, respectively (P < 0.001). Retinal vein occlusion and retinal macroaneurysm occurred in six eyes and one eye, respectively, during follow-up. Conclusion: Treatment with laser photocoagulation and/or intravitreal bevacizumab may be effective for Type 1 IMT, 36.7% of IMT eyes required no treatment over a 2-year follow-up, and other retinal vascular events were not uncommon.

The Relationship Between the Renin-Angiotensin–Aldosterone System and NMDA Receptor-Mediated Signal and the Prevention of Retinal Ganglion Cell Death

Purpose Excitotoxicity, which is due to glutamate-induced toxic effects on the retinal ganglion cell (RGC), is one of several mechanisms of RGC loss. The renin-angiotensin-aldosterone system (RAAS) has also been implicated in RGC death. Therefore, it is important to determine the exact relationship between the RAAS and N-methyl-d-aspartate (NMDA) receptor-mediated signal in order to prevent RGC death. Methods N-methyl-d-aspartate or aldosterone was injected into the vitreous body. After intravitreal injection of NMDA or aldosterone, animals were treated with spironolactone or memantine. Retinal damage was evaluated by measuring the number of RGCs at 4 weeks after local administration of aldosterone or at 2 weeks after local administration of NMDA. Vitreous humor levels of aldosterone were measured using enzyme immunoassay kits. Results A significantly decreased number of RGCs were observed after intravitreal injection of NMDA. Although spironolactone did not show any neuroprotective effects, memantine significantly reduced NMDA-induced degeneration in the retina. Furthermore, a significant decrease in the number of RGCs was observed after an intravitreal injection of aldosterone. While memantine did not exhibit any neuroprotective effects, spironolactone caused a significant reduction in the aldosterone-induced degeneration in the retina. There was no change in the aldosterone concentration in the vitreous humor after an NMDA injection. Conclusion Our findings indirectly show that there is no relationship between the RAAS and NMDA receptor-mediated signal with regard to RGC death.

Investigation of Drug–Drug Interactions Between Ritobegron, a Selective β3‐Adrenoceptor Agonist, With Probenecid in Healthy Men

We evaluated the effects of probenecid, a potent organic anion transporter 1 (OAT1) and OAT3 inhibitor, on the pharmacokinetics and safety of ritobegron, a selective β3‐adrenoceptor agonist, in healthy men. Twelve healthy men were administered a single oral dose of ritobegron (20 mg) alone or in combination with probenecid 2 hours before administration of ritobegron. In the combination sequence, additional doses of probenecid were administered 4 and 10 hours after the administration of ritobegron. Probenecid increased the Cmax of KUC‐7322, an active form of ritobegron, and the AUC0–48 h by 1.39 and 2.93 times, respectively. Probenecid prolonged the t1/2 of KUC‐7322 from 1.6 to 3.4 hours and decreased the renal clearance and cumulative fraction of KUC‐7322 excreted in urine from 18.5 to 4.9 L/h and from 64.7% to 49.7%, respectively. Coadministration of probenecid did not influence adverse events, blood pressure, pulse rate, or heart rate relative to ritobegron alone. Although probenecid inhibited renal tubule secretion of KUC‐7322 via OAT3 and increased KUC‐7322 exposure, it did not influence adverse effects or vital signs. Therefore, clinically significant drug–drug interactions are unlikely to occur when probenecid is administered in combination with OAT3 inhibitors or substrates.

Anti-Vascular Endothelial Growth Factor Therapy for Macular Edema following Central Retinal Vein Occlusion: 1 Initial Injection versus 3 Monthly Injections

Purpose: To compare the 12-month efficacy of 1 initial intravitreal injection of an anti-vascular endothelial growth factor (VEGF) agent followed by pro re nata (PRN) dosing with that of 3 initial monthly injections followed by PRN dosing in patients with macular edema (ME) after central retinal vein occlusion (CRVO). Methods: Twenty-nine eyes received 1 initial injection (1+PRN group) and 20 received 3 monthly injections (3+PRN group). Results: At month 12, changes in logMAR visual acuity from baseline were -0.172 ± 0.372 and -0.142 ± 0.317 in the 1+PRN and 3+PRN groups, respectively; the difference was not significant (p = 0.769). The number of anti-VEGF injections administered in the 3+PRN group (5.9 ± 2.1) was significantly greater than that in the 1+PRN group (4.1 ± 2.8; p = 0.022). Conclusion: When used for ME after CRVO, a 1+PRN regimen achieved 12-month outcomes similar to those of a 3+PRN regimen with fewer injections.

Elevated plasma aldosterone levels are associated with a reduction in retinal ganglion cell survival

Objective: The purpose of this article is to investigate the relationship between the plasma concentration of aldosterone and changes in the number of retinal ganglion cells (RGCs) after systemic administration of aldosterone. Methods: An osmotic minipump that was subcutaneously implanted into the midscapular region of rats administered 40, 80 or 160 μg/kg/day aldosterone or vehicle. Enzyme immunoassay kits were used to measure the plasma aldosterone concentrations two weeks after the systemic administration of aldosterone or vehicle. Six weeks after these systemic administrations, the number of RGCs was measured. Results: The plasma aldosterone concentrations at two weeks after systemic administration of vehicle or 160 μg/kg/day aldosterone were 238 ± 17 pg/ml and 1750 ± 151 pg/ml (748.5% ± 183.2%), respectively. There was a significant decrease in the number of RGCs in the central retina of the rats after the administration of either 80 or 160 μg/kg/day aldosterone. In the peripheral retina, however, there was a significant decrease in the number of RGCs in 40, 80 or 160 μg/kg/day aldosterone. There was a significant correlation between the number of RGCs and plasma aldosterone concentration. Conclusions: After systemic administration of aldosterone, there was a negative correlation between the plasma aldosterone concentration and the number of RGCs.