Robert T. Koda

Mitomycin-C concentration in human aqueous humour following trabeculectomy.

The aim of the study was to determine mitomycin-C (MMC) concentrations in human aqueous humour during trabeculectomy and to correlate anterior chamber concentrations with method of application. MMC was applied intra-operatively by saturating sponges, ranging in size from 2 × 2 × 5 mm to 2 × 4 × 10 mm on dry cut, with 0.5 mg/ml MMC during trabeculectomy for 3–5 minutes. Applications to episclera were made in 18 cases and to the scleral bed after scleral flap dissection in 9 cases. Aqueous samples were collected by paracentesis with a 30 gauge needle 2–7 minutes after removal of sponge and external irrigation. Aqueous MMC concentrations were determined by high-performance liquid chromatography. Aqueous MMC concentration in 27 samples ranged from below minimum detectable concentration (less than 5 ng/ml) to 120.8 ng/ml. Mean aqueous drug levels obtained when the applications were to the scleral bed were 35.65 ± 39.17 ng/ml (range 5–120.8 ng/ ml). Applications on episclera gave mean aqueous concentrations of 4.98 ± 9.11 ng/ml (range 0–33.3 ng/ml). The difference was statistically significant (p = 0.004). There were no correlations between sponge size, time of MMC exposure and aqueous MMC level. In conclusion, MMC is detectable in aqueous humour within minutes of external application and the aqueous concentration level is higher if the application is in the scleral bed than on the episclera. Toxicity of the drug at this concentration range for corneal endothelial cells needs further investigation via in vitro and clinical studies.

Effect of Vehicles and Penetration Enhancers on the In Vitro and In Vivo Percutaneous Absorption of Methotrexate and Edatrexate Through Hairless Mouse Skin

AbstractPurpose. Low-dose methotrexate (MTX) is approved for the treatment of recalcitrant rheumatoid arthritis (RA). The objective of this study was to determine the effect of vehicles and penetration enhancers on the percutaneous absorption of MTX and its analog edatrexate (EDAM), and develop transdermal (TD) delivery systems of the drugs for the treatment of RA. Methods. From previously published pharmacokinetic parameters with low-dose MTX therapy, and considering a 50 cm2 diffusional area, the target steady state in vitroTD flux for MTX was calculated to be 35 μg/cm2/hr. Modified Franz diffusion chambers and hairless mouse skin were used for in vitro skin permeation studies. Hairless mice were used for in vivo studies. Delivered amounts of MTX and EDAM were determined by assaying the receiver phase fluid (or blood) with validated reversed phase HPLC methods. Results. Intrinsic partition coefficient of MTX was low (log P = −1.2). Target MTX fluxes of ≥ 35 μg/cm2/hr were achievable only with 1−15% (v/v) Azone® in propylene glycol (PG). Flux of EDAM (85 μg/cm2/hr) was higher than MTX from an isopropyl alcohol (IPA)—5% (v/v) Azone® system. Clinically significant steady state in vivo blood concentration of MTX and EDAM was achieved using delivery systems containing ≥ 2.5% Azone® in PG. Area under the drug concentration-time curves (AUC0−24hr) for MTX were 2379 and 3534 ng*hr/ml from PG—2.5% Azone® and PG—7.5% Azone® systems respectively. AUC0-24hr of EDAM was 6893 ng*hr/ml using a PG—2.5% Azone® system. Conclusions. Results of this study show the feasibility of using a transdermal delivery system of MTX and EDAM for the treatment of rheumatoid arthritis.

Development of a simple, rapid and reproducible HPLC assay for the simultaneous determination of hypericins and stabilized hyperforin in commercial St. John's Wort preparations

A reversed-phase HPLC method was developed and validated for the simultaneous determination of hypericins and stabilized hyperforin in St. Johns wort extract. The sample solution was prepared by extraction of the finely powdered extract with methanol-water (80:20, v/v) containing 5% HP-beta-cyclodextrin, and adjusted to pH 2.5 with orthophosphoric acid. Diluted extract solutions, maintained at 0 degrees C, were injected into a C18 column. The samples were eluted isocratically using a mobile phase consisting of acetonitrile and 0.3% v/v phosphoric acid (90:10, v/v) at a 1.5 ml/min flow rate with simultaneous fluorescence (315/590 nm, excitation/emission) and UV (273 nm) detection. Quantification of the marker compounds (hypericin, pseudohypericin, hyperforin) was achieved by use of standard curves generated by plotting peak heights versus concentrations. Validation studies demonstrated that this HPLC method is simple, rapid, reliable, and reproducible. The standard curves were linear over the concentration ranges, 0.5-2.5 microg/ml (hypericin), 0.35-1.6 microg/ml (pseudohypericin) and 5-50 microg/ml (hyperforin). The intra-day coefficients of variation obtained for hypericin, pseudohypericin and hyperforin were < or = 4.4%, < or = 5.4%, and < or = 2.8%, respectively; inter-day CVs were < or = 5.8%, < or = 4.9%, and < or = 2.5%, respectively. This method may be applied for the routine standardization of St. Johns wort products against hyperforin and the hypericins, the putative antidepressant principles in the herbal.

Glucosamine and chondroitin sulfates in the treatment of osteoarthritis: a survey.

For more than 30 years, non-steroidal anti-inflammatory drugs (NSAIDs) have been used as standards in the treatment of osteoarthritis (OA). Serious and often life-threatening adverse effects due to these agents are common. Clinical findings have revealed that glucosamine sulfate and chondroitin sulfate are effective and safer alternatives to alleviate symptoms of OA. Experimental evidence indicates that these compounds and their low molecular weight derivatives have a particular tropism for cartilage where they serve as substrates in the biosynthesis of component building blocks. This paper is a literature review of the chemistry, mechanism of action, pharmacokinetics, clinical efficacy and safety of these two nutraceuticals.

Buccal and Percutaneous Absorptions

Buccal absorption of 31 aromatic and aliphatic acids and 10 basic drugs in human subjects has been found to be parabolically dependent on the log P, where P is the l-octanol-water partition coefficient. The ideal lipophilic character (log Po) for maximum buccal absorption is found to range from 4.2 to 5.5. The log of the permeability constant of a series of alcohols and steroids has been found to be linearly dependent upon the log of the partition coefficient measured in three different solvent systems.

Acetaminophen Does Not Impair Clearance of Zidovudine

OBJECTIVE To determine whether concurrent treatment with acetaminophen and zidovudine impairs clearance of zidovudine, thereby increasing the risk for zidovudine-induced hematologic toxicity. DESIGN Dose escalation, drug interaction study. SETTING University clinical research center. PATIENTS Patients with the acquired immunodeficiency syndrome (AIDS) or advanced AIDS-related complex. INTERVENTIONS Acetaminophen and 200 mg of zidovudine simultaneously every 4 hours. For 13 patients, the unit dosage of acetaminophen was 325 mg for 3 days; for 8 patients, the dosage was 650 mg for 3 days; and, for 6 patients, the dosage was 650 mg for 7 days. MEASUREMENTS Zidovudine clearance and production of the glucuronide conjugate of zidovudine were assessed after acetaminophen treatment. MAIN RESULTS Neither zidovudine clearance nor production of the glucuronide conjugate of zidovudine was impaired after treatment with acetaminophen. Clearance of zidovudine was actually accelerated by 5%, 11%, and 33% with the three acetaminophen regimens, respectively (P = 0.002 by analysis of variance; P = 0.04 for linear trend when changes in the area-under-the-curve for zidovudine were compared). CONCLUSION Because serum concentrations of zidovudine decrease after the coadministration of acetaminophen, a pharmacokinetic interaction between zidovudine and acetaminophen is unlikely to increase the risk for hematologic toxicity associated with zidovudine.

Determination of hydroxyurea in plasma and peritoneal fluid by high-performance liquid chromatography using electrochemical detection

A sensitive method has been developed for the determination of hydroxyurea in plasma and peritoneal fluid using reversed-phase high-performance liquid chromatography (HPLC) with electrochemical detection. Plasma or peritoneal fluid samples were treated with acetonitrile to precipitate proteins then injected to the HPLC. A C18 analytical column was used to separate hydroxyurea from interfering substances in the biological matrix. The mobile phase, consisting of 0.2 M sodium perchlorate-methanol (95:5, v/v) adjusted to pH 5.0, was delivered isocratically at a flow-rate of 1 ml/min and hydroxyurea was detected using a glassy-carbon electrode operating at an applied potential of +800 mV. Hydroxyurea eluted with a retention time of 3 min. The cycle time for analysis is short and the assay precision is acceptable (C.V. plasma=1.4-3.9%. C.V. peritoneal fluid=2.1-9.7%). The method has been validated and is linear from 25 to 400 ng/ml in plasma and 5 to 30 ng/ml in peritoneal fluid. The method has been shown to be applicable for pharmacokinetic studies.

Determination of the antimitotic agents N-Desacetylcolchicine, demecolcine and colchicine in serum and urine

In an effort to characterize the pharmacokinetic behavior of the antimitotic agent N-desacetylcolchicine a selective, sensitive high-performance liquid chromatographic method was developed for the determination of N-desacetylcolchicine, demecolcine and colchicine in serum or urine. To 0.5 ml of serum or 0.1 ml of urine diluted to 0.5 ml were added 50 microliters demecolcine (2 micrograms/ml) which serves as the internal standard. The sample was extracted using a C2 reversed-phase solid extraction column. N-Desacetyl-colchicine, colchicine and the internal standard were eluted from the column with methanol. The combined eluates were evaporated to dryness and the residue was reconstituted with water. The reconstituted sample was injected into a C18 reversed-phase column and eluted using a mobile phase consisting of 0.1 M potassium dihydrogenphosphate, 5 mM 1-pentanesulfonic acid in methanol and acetonitrile with a final pH of 6.0, at a flow rate of 1.5 ml/min. N-Desacetylcolchicine, colchicine and the internal standard were detected using a variable-wavelength ultraviolet detector at 254 nm. The limit of detection was 0.4 ng/ml for desacetylcolchicine and 4.0 ng/ml for colchicine. The method is linear over a concentration range of 1.0-200 ng/ml. The method has been shown to be a rapid, reliable method to monitor N-desacetylcolchicine levels in clinical trials in cancer patients.

Determination of mitomycin C in human aqueous humor and serum by high-performance liquid chromatography

Mitomycin C (MMC) is used in the treatment of disseminated adenocarcinoma of the stomach and pancreas and is used in ophthalmology as adjunctive therapy in trabeculectomy. Since only small volumes of aqueous humor are available for analysis, a sensitive method requiring limited sample preparation was developed. An internal standard, 4-aminoacetophenone, was added to aqueous humor specimens, and the solution was directly injected into the high-performance liquid chromatographic (HPLC) column. The use of a short 50-mm C18 reversed-phase column gave adequate resolution of peaks with improved sensitivity. The method was applicable for determination of MMC in serum, although solid-phase extraction for sample clean-up was required prior to injection into the HPLC column, and analytical columns of 150-250 mm were necessary for adequate resolution of peaks. The method has been validated and is linear from 6.25 to 50 ng/ml in aqueous humor and from 10 to 500 ng/ml in serum.

Diffusion of Drugs into Prostatic Fluid and Milk

THE PROSTATIC FLUID/PLASMA CONCENTRATION RATIO of various sulfonamides, antibiotics and antibacterial agents, and the milk/plasma ratio of sulfonamides and basic drugs have been quantitatively correlated with the degree of dissociation, as represented by log U/D, and the partition coefficient (log P). Because of the lower pH values of the prostatic fluid (6.6) and milk (6.8) as compared with the plasma pH (7.4), the degree of dissociation appears to be the most important factor in determining the distribution of these weak acids or bases. Partition coefficient also plays a secondary role. The log Po for maximum diffusion into milk is lower than that for maximum gastrointestinal, buccal or percutaneous absorption. This may be attributed to plasma protein binding which prevents diffusion of the drug from the blood circulation into the milk since high lipophilicity favors protein binding. The clinical implications of the correlations obtained are discussed.