Pharmacokinetics of trimetrexate and dapsone in AIDS patients with Pneumocystis carinii pneumonia.

The objective of this study was to determine the pharmacokinetics of trimetrexate and dapsone in AIDS patients with moderate to severe pneumocystis pneumonia. Trimetrexate, leucovorin, and dapsone were administered for 21 +/- 3 days in the following doses: trimetrexate glucuronate, 45 mg/m2; leucovorin, 20 mg/m2; and dapsone, 100 mg daily. The pharmacokinetics of trimetrexate, dapsone, and dapsone's metabolite, monoacetyldapsone, were determined at three separate periods over the course of treatment. Serial blood samples were obtained over 24 hours after dosing and analyzed for trimetrexate, dapsone, and monoacetyldapsone, and pharmacokinetic parameters were determined. The mean parameters obtained for the early, mid-, and late collection periods were the following: trimetrexate: t1/2 = 8.29, 9.15, 10.00 hr; AUC = 16.85, 22.38, 24.49 mg.hr/l; CI = 5.58, 4.14, 3.96 l/hr, respectively. DDS: t1/2 = 14.99, 16.59, 15.13 hr; AUC = 30.60, 35.29, 36.08 mg.hr/l; CI = 3.82, 3.49, 3.01 l/hr, respectively. Monoacetyldapsone: t1/2 = 20.25, 18.66, 16.32 hr; AUC = 24.05, 24.06, 23.86 mg.hr/l, respectively. No statistically significant changes in pharmacokinetics for trimetrexate or dapsone were observed over the 21 +/- 3 day course of treatment. The results suggest that there are no major interactions between trimetrexate and dapsone when administered together in acutely ill patients.

Phase I study of AG 331, a novel thymidylate synthase inhibitor, in patients with refractory solid tumors.

PURPOSE: This was a phase I study of AG 331 to determine systemic tolerance and pharmacokinetics following single and multiple escalating intravenous doses. METHODS: The study was an open-label phase I trial that was divided into two components. In phase IA (single dose), six dose levels from 12.5 to 225 mg/m2 were administered to 18 patients (3 at each dose level) and serial blood samples were collected for 72 h. Upon achieving satisfactory pharmacologic parameters, the multiple dosing component (phase IB) was initiated. Six dose levels from 50 to 800 mg/m2 per day were administered for 5 consecutive days to 18 patients. Pre- and postdose blood samples were obtained on days 1-4 and serial blood samples were collected over 24 h following dose 5. Nonhematologic and hepatic toxicities were assessed, serum AG 331 concentrations were measured and pharmacokinetic parameters determined. RESULTS: Other than fatigue, no severe toxicities were encountered in phase IA. Liver toxicity was manifested by elevations in transaminase first noted at multiple doses of 200 mg/m2 per day for 5 days. Fever and malaise but no myelosuppression were noted. The mean terminal t1/2 following single doses was significantly shorter than the t1/2 following multiple dosing (6.8 vs 9.9 h) and clearance was significantly faster following single doses than following multiple dosing (81.7 vs 30.4 l/h), but no significant difference in Vd was noted. CONCLUSIONS: The dose-related toxicity profile precludes further clinical development at this time. The pharmacokinetics of AG 331 following single and multiple doses showed significant differences.

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.

Fluorometric determination of methyldopa in biological fluids.

A fluorometric method for the analysis of methyldopa, based on the formation of a fluorophore after oxidation and rearrangement, is described. The drug is isolated from biological fluids by adsorption on alumina and elution with an organic solvent. Fluoresence is linear from 0.1 to 1.5 microgram of methyldopa/ml. The assay has a lower limit of sensitivity of 100 ng/ml and is suitable for pharmacokinetic studies following therapeutic doses in animals and humans.

Rapid GLC determination of fusaric acid in biological fluids.

A simple, sensitive GLC assay was developed for fusaric acid, the active metabolite of bupicomide, to follow the disposition of this investigational antihypertensive agent in patients undergoing therapy. Fusaric acid is efficiently extracted from biological samples, derivatized by on-column methylation, and chromatographed using flame-ionization detection. An internal standard is utilized to quantitate results. The procedure is rapid and specific for fusaric acid, and has a lower limit of sensitivity of 0.1 mug/ml. The method is suitable for supporting pharmacokinetic studies of bupicomide following therapeutic doses in animals and humans.

Effects of external irrigation on mitomycin-C concentration in rabbit aqueous and vitreous humor.

PURPOSE: These experiments were performed to determine what effect external irrigation with balanced salt has on limiting penetration of mitomycin-C into the aqueous and vitreous. METHODS: Bilateral 5 min scleral applications of mitomycin-C (0.5 mg/ml) were performed in 21 rabbits using identical 6x4x1 mm cellulose sponges uniformly soaked with 0.2 ml of the mitomycin-C solution. Irrigation of one eye, randomly selected, was then carried out with 10 ml of balanced salt solution over 1 min. High performance liquid chromatography was used to analyse aqueous and vitreous samples obtained from separate animals at 5, 15, 30, and 60 min and at 2,4, and 6 h after sponge removal. RESULTS: Nonirrigated eyes demonstrated continual rise in aqueous mitomycin-C concentration over 1 h. Irrigated eyes demonstrated lower mitomycin-C concentrations at all times studied and a continual fall in aqueous concentration after 15 min. Vitreous mitomycin-C was detected in both groups only at 5 min. CONCLUSIONS: Irrigation with balanced salt substantially reduces intraocular diffusion of mitomycin-C.

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. John's 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. John's wort products against hyperforin and the hypericins, the putative antidepressant principles in the herbal.

Oculotoxicities of systemically administered drugs.

There have been many drugs reported to cause oculotoxic responses after their systemic administration. The severity of these toxicities range from minor ocular inconvenience to permanent loss of vision. This paper reviews the current literature and attempts to suggest some probable factors involved in the development of oculotoxicities by systemic drugs. Various drug entry and exit pathways in the eye are presented and the role of some intraocular structures in the toxicity development is examined. The issues of melanin binding, genetic heterogeneity, photosensitivity and environmental pollution are discussed.

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.

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.

The ocular distribution of bunolol in the eyes of albino and pigmented rabbits.

The ocular administration of a 50 microL instillation of bunolol hydrochloride, a beta 1- and beta 2- adrenoceptor blocking agent, resulted in significantly higher drug levels in the choroid/retina, iris, and ciliary body of pigmented rabbits compared with albino rabbits following topical administration. The concentrations in these tissues also persisted longer in the pigmented rabbits' eyes. However, no statistically significant differences in tissue levels were observed in the cornea or conjunctiva. The results of this study support the previously reported finding with timolol which showed longer retention of the drug in the iris, ciliary, choroid, and retina of pigmented rabbits than albinos.

Effect of vehicles and penetration enhancers on the in vitro and in vivo percutaneous absorption of methotrexate and edatrexate through hairless mouse skin.

PURPOSE: 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 vitro TD flux for MTX was calculated to be 35 micrograms/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 > or = 35 micrograms/cm2/hr were achievable only with 1-15% (v/v) Azone in propylene glycol (PG). Flux of EDAM (85 micrograms/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 > or = 2.5% Azone in PG. Area under the drug concentration-time curves (AUC0-24 hr) for MTX were 2379 and 3534 ng*hr/ml from PG-2.5% Azone and PG-7.5% Azone systems respectively. AUC0-24 hr 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.

Pharmacokinetics, pharmacology of atenolol and effect of renal disease.

1. The pharmacokinetics of intravenous and oral atenolol (50 mg) in six healthy volunteers was studied. Plasma, saliva and urine were collected up to 24 h after each dose. 2. There was no significant difference in atenolol half-life when administered by the two routes. Bioavailability of the orally administered atenolol was 50%. 3. Atenolol levels in saliva required about 2 h to reach equilibrium with plasma drug levels. 4. A comparison between the pharmacokinetics and pharmacology of atenolol was made in twelve healthy subjects. 5. Dose-independent pharmacokinetics were observed. Reductions in resting heart rate and arterial blood pressure were proportional to either the logarithm of dose or area under the plasma concentration time curve or cumulative urinary atenolol excretion. 6. Plasma elimination half-life in five subjects with renal failure was prolonged.

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.

Phase I and pharmacologic study of i.v. hydroxyurea infusion given with i.p. 5-fluoro-2'-deoxyuridine and leucovorin.

Preclinical data suggests that the action of fluoropyrimidines may be enhanced by the addition of hydroxyurea. We developed a phase I trial to determine the maximum tolerated dose and pharmacokinetics of i.v. hydroxyurea (HU) in combination with i.p. 5-fluoro-2'-deoxyuridine (FUdR) and leucovorin (LV). Eligible patients had metastatic carcinoma confined mostly to the peritoneal cavity, and adequate hepatic, renal and bone marrow function. Patients were treated with a fixed dose of FUdR (3 g) and LV (640 mg) administered on days 1--3. HU was administered as a 72-h infusion starting simultaneously with i.p. therapy on day 1. The following dose levels were studied: 2.0, 2.5, 3.0 and 3.6 g/m(2)/day. Pharmacokinetics were studied in blood and peritoneal fluid. Twenty-eight patients were accrued. Steady-state plasma and peritoneal fluid HU levels increased with increasing dose, and steady state was achieved within 12 h of continuous dosing. The steady-state HU plasma:peritoneal fluid concentration ratio ranged from 1.06 x 10(3) to 1.25 x 10(3) and the plasma HU clearance ranged from 4.63 to 5.81 l/h/m(2). Peritoneal fluid AUC = 137,639 +/- 43,914 microg/ml x min, t(1/2) = 100.9 +/- 56.4 min and Cl = 25.29 +/- 10.88 ml/min. Neutropenia represented the dose-limiting toxicity. We conclude that i.p. FUdR and LV in combination with i.v. HU is well tolerated. The addition of systemic HU increased the incidence of myelosuppression.