Comparison of 3 vancomycin dosage regimens during hemodialysis with cellulose triacetate dialyzers: post-dialysis versus intradialytic administration.

AIMS: Traditionally, vancomycin is administered following dialysis to minimize drug loss when high-flux membranes are employed. Unfortunately, this approach is extremely inconvenient for patients and staff, requiring the patients to remain in the unit for at least 1 hour following dialysis. This study was designed to evaluate the feasibility of administering vancomycin during hemodialysis. Specifically, this study was designed to compare the pharmacokinetics of vancomycin when administered during the last 1-2 hours of dialysis (i.e. intra-dialytic administration) to that administered after completion of dialysis. MATERIALS AND METHODS: In a randomized, 3-way crossover trial, the pharmacokinetics of vancomycin were evaluated in 9 hemodialysis patients, comparing vancomycin 15 mg/kg following dialysis (Phase I), vancomycin 15 mg/kg during the last hour of hemodialysis (Phase II) or vancomycin 30 mg/kg during the last 2 hours of hemodialysis (Phase III). Vancomycin plasma concentrations were obtained over an 8-day period and subsequent comparisons between the treatment approaches were made with paired t-tests or ANOVA, as appropriate. Dialysate vancomycin concentrations determined on Day 1 and Day 3 of Phases II and III were used to calculate the fraction of vancomycin dose removed, and were compared to plasma data using paired t-tests. RESULTS: Vancomycin was significantly removed (33.4 to 39.5%) during a 3- to 4-hour high-flux dialysis session occurring on Day 3 after vancomycin administration. Mean serum concentrations immediately following intradialytic vancomycin administration of 15 mg/kg over the last hour of dialysis or 30 mg/kg over the last 2 hours of dialysis were initially high (77.7 and 95.5 mcg/ml respectively), but fell to 25.9 and 40.5 mcg/ml, respectively, by 4 hours post-dialysis. Predialysis concentrations on Days 3, 5 and 8 were similar for vancomycin 30 mg/kg administered over the last 2 hours of dialysis as compared with a 15 mg/kg dose given after dialysis. Vancomycin 15 mg/kg over the last hour of dialysis resulted in significantly lower subsequent predialysis concentrations than the other dosing schemes. CONCLUSIONS: Vancomycin administration of 30 mg/kg over the last 2 hours of dialysis achieves serum concentrations similar to conventional dosing of 15 mg/kg after dialysis and would allow dosing on a weekly basis.

Sildenafil inhibits hypoxia-induced pulmonary hypertension.

BACKGROUND: This study investigated the effect of the phosphodiesterase 5 inhibitor sildenafil on the pulmonary vascular response to hypoxia in humans and mice. METHODS AND RESULTS: In a randomized, double-blind study, sildenafil 100 mg or placebo was given orally to 10 healthy volunteers 1 hour before breathing 11% O(2) for 30 minutes. Pulmonary artery pressure (PAP) was measured with an indwelling right heart catheter. The acute 56% increase in mean PAP produced by hypoxia during placebo treatment (mean PAP [mean+/-SD mm Hg]: normoxia 16.0+/-2.1 versus hypoxia 25.0+/-4.8) was almost abolished by sildenafil (normoxia 16.0+/-2.1 versus hypoxia 18.0+/-3.6), with no significant effect on systemic blood pressure. In the isolated perfused lung of wild-type and endothelial nitric oxide synthase (eNOS)-deficient mice, sildenafil markedly blunted acute hypoxic pulmonary vasoconstriction. Wild-type mice dosed orally with the drug (25 mg. kg(-1). d(-1)) throughout 3 weeks of exposure to hypoxia (10% O(2)) exhibited a significant reduction in right ventricular systolic pressure (placebo versus sildenafil: 43.3+/-9.9 versus 29.9+/-9.7 mm Hg, P<0.05) coupled with a small reduction in right ventricular hypertrophy and inhibition of pulmonary vascular remodeling. In eNOS mutant mice, sildenafil attenuated the increase in right ventricular systolic pressure but without a significant effect on right ventricular hypertrophy or vascular remodeling. CONCLUSIONS: Sildenafil attenuates hypoxia-induced pulmonary hypertension in humans and mice and offers a novel approach to the treatment of this condition. The eNOS-NO-cGMP pathway contributes to the response to sildenafil, but other biochemical sources of cGMP also play a role. Sildenafil has beneficial pulmonary hemodynamic effects even when eNOS activity is impaired.

Characterization of adenylyl cyclase isoforms in rat peripheral pulmonary arteries.

Activation of adenylyl cyclase (AC), of which there are 10 diversely regulated isoforms, is important in regulating pulmonary vascular tone and remodeling. Immunohistochemistry in rat lungs demonstrated that AC2, AC3, and AC5/6 predominated in vascular and bronchial smooth muscle. Isoforms 1, 4, 7, and 8 localized to the bronchial epithelium. Exposure of animals to hypoxia did not change the pattern of isoform expression. RT-PCR confirmed mRNA expression of AC2, AC3, AC5, and AC6 and demonstrated AC7 and AC8 transcripts in smooth muscle. Western blotting confirmed the presence of AC2, AC3, and AC5/6 proteins. Functional studies provided evidence of cAMP regulation by Ca(2+) and protein kinase C-activated but not G(i)-inhibited pathways, supporting a role for AC2 and a Ca(2+)-stimulated isoform, AC8. However, NKH-477, an AC5-selective activator, was more potent than forskolin in elevating cAMP and inhibiting serum-stimulated [(3)H]thymidine incorporation, supporting the presence of AC5. These studies demonstrate differential expression of AC isoforms in rat lungs and provide evidence that AC2, AC5, and AC8 are functionally important in cAMP regulation and growth pathways in pulmonary artery myocytes.

Parenteral iron use in the management of anemia in end-stage renal disease patients.

Intravenous iron is required by most dialysis patients receiving erythropoietin (EPO) to maintain an adequate hematocrit. In the United States, there are currently two parenteral iron preparations, iron dextran and iron gluconate, approved for such use, and a third product, iron sucrose, is under development. This article reviews each of these products. Each of the iron products increases the efficacy of EPO use in anemia management. There is considerable experience in the United States and elsewhere with the use of iron dextran. Although it is clinically effective, iron dextran is also associated with significant morbidity from both dose-dependent and -independent side effects. The slow release of iron from this complex necessitates a delay in monitoring iron indices after the administration of large doses of iron dextran. Recommended doses of iron sucrose appear very safe with little risk of anaphylactic reactions. Adverse effects are uncommon and not life threatening. If approved for use in the United States, iron sucrose may be a safe and effective alternative to iron dextran. Iron dissociates from iron gluconate quite rapidly and may increase the production of ionized free iron. Iron gluconate may be a safe alternative to iron dextran for patients with severe reactions, including anaphylaxis. The risk of allergic reactions to iron gluconate is very low. The exact place in therapy for the newer iron complexes remains unclear. Currently available data suggest that iron sucrose and iron gluconate may have diminished adverse effect profiles when compared with iron dextran. Additional clinical experience will establish the role for these new iron products.

Intravenous iron products.

Intravenous iron has been used extensively and successfully as part of the treatment of anemia in dialysis patients. Iron dextran can be used safely, however, there is a slight risk of severe, anaphylactoid reactions. Iron gluconate and iron sucrose are less likely to cause hypersensitivity reactions. These products should be safe and effective alternatives to iron dextran.

High expression of endothelial nitric oxide synthase in plexiform lesions of pulmonary hypertension.

The pathogenesis of pulmonary hypertension (PH) remains poorly understood. Vasoconstriction, although likely to be a major factor in the disease, varies between patients and studies of a variety of vasoactive substances have sometimes yielded conflicting results. Amongst these substances, alteration of the nitric oxide (NO) system has been cited as a possible pathogenic factor but both reduction and elevation of the expression of endothelial NO-synthase (eNOS) have been reported in pulmonary vessels. The present study has used immunocytochemistry with well-characterized antibodies to eNOS to investigate its expression in lung tissue taken at transplantation from 44 patients with PH (22 primary, 22 secondary) and 12 non-hypertensive controls. Semi-quantitative assessment showed that although the levels of eNOS expression in pulmonary vessels were variable within both hypertensives and controls, a statistically significant (P < 0.01) reduction of immunoreactivity was found in small arterioles from hypertensives compared with controls. In contrast, consistently strong expression of eNOS was seen in the endothelium of plexiform lesions in both the primary and the secondary PH patients. Although a decrease in the NO system of patients with PH has been reported, these findings show a distinct regional distribution of the enzyme with particularly high levels in plexiform lesions, a previously unreported observation, and offer a new perspective on the disease and on the evaluation of possible novel therapeutic approaches.

Expression of inducible nitric oxide synthase and formation of peroxynitrite in posttransplant obliterative bronchiolitis.

BACKGROUND: Obliterative bronchiolitis is characterized histologically by inflammation, epithelial cell damage and loss, fibrosis, and eventual obliteration of airways. Production of high levels of the potential cytotoxin nitric oxide by inducible nitric oxide synthase has been implicated in several inflammatory diseases. The damaging effects of nitric oxide are mediated by peroxynitrite, are formed from nitric oxide and superoxide, and can be demonstrated by the detection of nitrotyrosine. Our previous finding of high inducible nitric oxide synthase expression in inflamed airway epithelium led us to hypothesize that release of nitric oxide in obliterative bronchiolitis mediates the characteristic epithelial damage. METHODS: Immunocytochemistry was carried out to seek expression of inducible nitric oxide synthase and nitrotyrosine in transplant samples from patients with obliterative bronchiolitis (n=10) and, as controls, unused donor lungs (n=5). RESULTS: Inducible nitric oxide synthase was strongly expressed in the damaged airway epithelium in obliterative bronchiolitis and in inflammatory cells, where its distribution was matched by that of nitrotyrosine. Normal controls showed little or no immunoreactivity for any of the antigens studied. CONCLUSIONS: Our findings suggest that nitric oxide may play a role in the pathogenesis of obliterative bronchiolitis and indicate that further work is essential to fully understand the processes and mechanisms involved.

Human lung mononuclear cells induce nitric oxide synthase in murine airway epithelial cells in vitro: role of TNFalpha and IL-1beta.

Nitric oxide (NO) is a gas released by the airway epithelium, but the mechanism regulating NO release is unclear. We hypothesized that lung mononuclear cell release of tumor necrosis factor alpha (TNF) and interleukin-1beta (IL-1) would induce epithelial cells to release NO. Lung mononuclear cells were obtained from seven normal volunteers by bronchoalveolar lavage and cultured with Escherichia coli lipopolysaccharide for 24 h. The mononuclear cell culture-conditioned media (M-CM) were then applied to cultures of the murine lung epithelial cell line, LA-4. Nitrite and nitrite + nitrate concentrations were 0.9 +/- 0.1 and 11.8 +/- 2.4 microM in the M-CM. Culturing LA-4 cells line with the M-CM (1:10 dilution) resulted in a marked and time-dependent increase in nitrite or nitrite + nitrate compared with LA-4 cells cultured in media alone (2.4 +/- 0.5 versus 0.9 +/- 0.1 microm and 16.6 +/- 0.6 versus 11.8 +/- 2.4 microM after 24 h). Antibodies to TNF and/or IL-1 significantly reduced the nitrite or nitrite + nitrate concentrations and the concentrations of TNF and IL-1 in the M-CM correlated with nitrite concentrations in the LA-4 culture supernatant fluids (r2 = 0.848 and 0.956). Inducible nitric oxide synthase (iNOS) protein and mRNA examined by immunohistochemistry and Northern blot analysis revealed a marked elevation in the cells cultured with the M-CM which was significantly reduced by TNF and IL-1 antibodies. These data demonstrate that mononuclear cells can stimulate LA-4 cells to express iNOS by releasing TNF and IL-1.

Calcitriol in the management of secondary hyperparathyroidism of renal failure.

Secondary hyperparathyroidism (HPT) is characterized by persistent hypersecretion of parathyroid hormone (PTH), and produces characteristics of hyperparathyroid bone disease and a variety of biochemical and hormonal derangements. Management of uremic secondary HPT involves both prevention and treatment. Among preventive measures are attempts to control serum phosphate and serum calcium concentrations through dietary restriction, administration of phosphate binders, and calcium supplementation. Treatment with a vitamin D analog such as calcitriol returns plasma calcium concentrations toward normal and suppresses PTH secretion. The availability of a parenteral formulation of calcitriol, and new information regarding alternative routes of administration and regimens employing oral pulse dosing have renewed interest in calcitriol for the management of uremic secondary HPT.

Influence of cellulose triacetate hemodialyzers on vancomycin pharmacokinetics.

This study was designed to evaluate the pharmacokinetics of vancomycin during hemodialysis with cellulose triacetate (CT) high-flux dialyzers and to assess the influence of membrane surface area on intradialytic clearance. In a randomized crossover fashion, the pharmacokinetics of vancomycin were evaluated during dialysis with the CT 110 and CT 190 membranes. Six hemodialysis patients received 1 g of vancomycin immediately after the completion of a dialysis session, and subsequently, blood samples were obtained over a 5-day study period. On Day 3 subjects were dialyzed with CT 110 or CT 190 membranes. The mean intradialytic clearance of vancomycin was 56.7 +/- 7.5 and 100.70 +/- 10.7 mL/min with the CT 110 and CT 190 membranes, respectively (P < 0.05). Significant rebound in vancomycin serum concentrations occurred after dialysis; this rebound appeared to be complete 3 h postdialysis. On the basis of postrebound concentrations, the apparent percent removal of vancomycin was 23.6 +/- 1.2 and 25.2 +/- 8.6% for CT 110 and CT 190 membranes, respectively (not significant). Vancomycin is significantly cleared during dialysis with cellulose triacetate membranes, and its clearance is dependent on membrane surface area. Although a small supplemental dose of vancomycin could be administered after dialysis to replace drug lost during dialysis, it may be more efficient to give a larger dose of vancomycin after several dialysis periods. The determination of vancomycin removal can be used to estimate vancomycin serum concentrations as well as dosage requirements. This in conjunction with serum concentration monitoring can be used to optimize vancomycin dosing.

Pharmacist participation in cardiopulmonary resuscitation.

Pharmacist participation in cardiopulmonary resuscitation (CPR), including the basic life support (BLS) activities of artificial respiration and chest compressions, was studied. A questionnaire was mailed in September 1991 to the 197 graduates (1986-90) of a Michigan college of pharmacy requiring BLS training for graduation. Another questionnaire was mailed in April 1992 to the 181 pharmacy directors at all general acute-care hospitals in Michigan. The "graduate" survey covered practice setting, current status of BLS certification, use of BLS, and attitudes toward BLS training. The "director" survey covered the characteristics of the institution and its pharmacists, pharmacist involvement in CPR, and departmental BLS-training requirements. The response rates for the graduate and director surveys were 81% (160 questionnaires) and 76% (138), respectively. Only 66 (41%) of the graduates were currently certified in BLS, and only 77 (48%) had completed a BLS course since graduation. More than half (84, or 53%) indicated they had never been involved in any CPR activity. Activities most likely to be reported were drug preparation, dosage calculation, documentation, and drug information; very few pharmacists had given artificial respiration or chest compressions. Forty-six (33%) of the directors indicated that pharmacists routinely were members of the CPR team. Most (59%) of these 46 hospitals did not require BLS training for pharmacists. Hospital size significantly affected whether pharmacists were included on the CPR team. Hospitals with decentralized pharmacists were more likely than hospitals with centralized pharmacists to have pharmacist involvement on the CPR team. Both study groups expressed ambivalence about the value of BLS training for their current pharmacy practice situations.(ABSTRACT TRUNCATED AT 250 WORDS)

Benefits and work-schedule options in hospital pharmacy practice.

Hospital pharmacy directors were surveyed to determine whether their departments offered specific family-related benefits and work-schedule options and how their attitudes about these options compared with those of female hospital pharmacists. Questionnaires were mailed to 300 randomly selected hospital pharmacy directors to collect the following information: vacancy rates and male:female ratios in hospital pharmacy positions, which of 13 selected benefits and work-schedule options were offered, barriers that prevented the other options from being offered, and attitudes about the listed options. The options included in the survey were selected because they represent ways of balancing home and work (e.g., maternity leave, job sharing, day care). The pharmacy directors' responses were compared with those from a similar survey of female hospital pharmacists. The usable response rate was 50.3%. Position vacancy rates ranged from 5.5% for directors to 35.8% for clinical supervisors. All full-time positions had an even distribution of men and women except for director and assistant or associate director positions. Of 13 options, only maternity leave, part-time schedules, and flexible schedules were offered by more than half of the hospitals. These three were also the only listed options that the respondents considered important in recruiting and retaining pharmacists. Barriers to offering other options included the perception that current benefits and work-schedule options were adequate, lack of staff coverage, lack of funds, and the perception that some positions are not compatible with alternative schedules. Respondents' ratings of the importance of the listed benefits and work-schedule options were significantly lower than ratings given by female hospital pharmacists in a separate survey.(ABSTRACT TRUNCATED AT 250 WORDS)

Benefits and work-schedule options for female hospital pharmacists.

Female hospital pharmacists were surveyed to determine what benefits and work-schedule options they want and how they feel about those currently offered. Questionnaires were mailed to 750 randomly selected female ASHP members to (1) collect employment and personal data, (2) determine which of 13 family-related benefits and work-schedule options were offered at their institutions, (3) assess use of and attitudes about these options, and (4) determine whether use and attitudes differ by position or parental status. The options included in the survey were selected because they represent ways of balancing home and work (e.g., job sharing, day care, parental leave). The usable response rate was 65.3%. About 59% were married and 40% had children. Most (83.3%) held full-time positions, and 36.5% held staff nonclinical positions. More than 70% of the respondents indicated that a flexible schedule, flextime, and maternity leave were important in combining personal and professional roles. Respondents indicated that many of the benefits and work-schedule options that were not routinely offered would be used to a great extent if offered. Forty percent reported satisfaction with current benefits and work-schedule options. Many surveyed female ASHP members considered their current benefits and work-schedule options less than optimal and would be interested in more flexible schedules and benefits.

Chronic hemodialysis patients. Part I: Characterization and drug-related problems.

OBJECTIVE: To describe medication use in hemodialysis patients and to characterize the potential drug-related problems that may occur in this population. DESIGN: All patients being dialyzed during the study period who were responsible for taking their own medications and who were able to provide an accurate medication history were included in this study. A pharmacist administered a structured medication history and drug therapy review protocol known as the Focused Drug Therapy Review Program to identify potential drug-related problems. This process was modified for a hemodialysis population. SETTING: Outpatient hemodialysis unit at a university-affiliated hospital. RESULTS: Thirty patients with endstage renal disease requiring hemodialysis were enrolled in the study. On average, 10 prescription and 2 prescribed nonprescription medications were used per patient. The incidence of potential adverse effects and medication allergies or intolerances averaged 5.5 and 2.2 per patient, respectively. Twenty patients (67 percent) reported missing an average of 3.4 (range 1-11) doses of medication per month. A total of 216 potential drug-related problems (encompassing both prescribing choices and patient behaviors) were identified by the pharmacist; the categories of drug selection and medication compliance contained the greatest number of potential problems (24 and 23 percent, respectively). CONCLUSIONS: Hemodialysis patients use a large number of medications, which increases the risk for adverse reactions and other drug-related problems. The types of potential drug-related problems identified are amenable to pharmacist input. Thus, such patients should be targeted for clinical pharmacy intervention.

Chronic hemodialysis patients. Part II: Reducing drug-related problems through application of the focused drug therapy review program.

OBJECTIVE: To test the value and measure the impact of a model of pharmacy practice called the Focused Drug Therapy Review Program (FDTRP) in patients with endstage renal disease on hemodialysis. DESIGN: A modified version of FDTRP, adapted for a hemodialysis population, was assessed for its impact on prescriber behavior. The impact was measured by examining the percentage of pharmacist therapeutic recommendations accepted and implemented by the prescriber. SETTING: Thirty patients at a university hospital-based outpatient hemodialysis unit participated in the study. Twenty-four patients completed the study through the implementation evaluation. RESULTS: The pharmacist generated 114 therapeutic recommendations and 85 informative comments regarding drug therapy. The prescriber accepted 76 percent and implemented 70 percent of the therapeutic recommendations. The prescriber considered the informative comments to be helpful, even if the information was known previously. CONCLUSIONS: The FDTRP has been shown to be useful in the care of chronic hemodialysis patients. In addition, the pharmacist was able to provide clinically important recommendations in a closely monitored patient population.

Consumer vinegar test for determining calcium disintegration.

A consumer test and standardized methods were compared for measuring the disintegration of calcium tablets, and the disintegration results were compared with results of dissolution testing to determine the ability of the consumer test of disintegration to predict bioavailability of calcium. Disintegration of 17 calcium supplement products, in tablet form, was studied in Simulated Gastric Fluid Test Solution, USP, without pepsin (GF), in distilled water, and in white distilled vinegar. For disintegration testing with GF and with distilled water, six tablets of each product were placed in an apparatus and immersed in the solution at 37 degrees C for 60 minutes. Six tablets of each product were tested in 200 mL of vinegar at room temperature for 30 minutes. Disintegration was determined by visual observation. Seven products were tested for dissolution in GF or water. Three samples of each product were tested at intervals over 120 minutes for calcium content. Results of testing with an ion-selective electrode were converted to milligrams and compared with the calcium content of the tablets (as claimed on the package label). The mean disintegration times of various calcium products in vinegar ranged from 1.8 to greater than 30 minutes. The mean time in distilled water and GF ranged from 1.6 to greater than 60 minutes and from 1.0 to greater than 60 minutes, respectively. Results were in agreement in 87% to 93% of cases between the consumer vinegar test and the standardized disintegration test methods, a significant correlation. No correlation was found between disintegration time and the extent of dissolution. The disintegration and dissolution of commercially available calcium tablets was highly variable.(ABSTRACT TRUNCATED AT 250 WORDS)