Comparison of native E. coli and PEG asparaginase pharmacokinetics and pharmacodynamics in pediatric acute lymphoblastic leukemia

Asparaginase (ASP) is used routinely in frontline clinical trials for the treatment of childhood acute lymphoblastic leukemia (ALL). The goals of this study were to assess the pharmacokinetics and pharmacodynamics of ASP and to mathematically model the dynamics between ASP and asparagine (ASN) in relapsed ALL. Forty children were randomized to receive either native or polyethylene glycolated (PEG) Escherichia coli ASP during reinduction therapy. Serial plasma ASP and ASN, cerebrospinal fluid (CSF) ASN, and serum anti-ASP antibody samples were collected. The ASP clearance was higher (P = 0.001) for native vs. PEG ASP. Patients with antibodies to PEG ASP had faster PEG ASP clearance (P = 0.004) than did antibody-negative patients. Patients who were positive for antibodies had higher CSF ASN concentrations than did those who were negative (P = 0.04). The modeling suggests that by modifying dosages, comparable ASN depletion is achievable with both preparations. At relapse, there were significant pharmacokinetic and pharmacodynamic differences attributable to ASP preparation and antibody status.

Asparaginase pharmacodynamics differ by formulation among children with newly diagnosed acute lymphoblastic leukemia

Polyethylene glycol-conjugated (PEG) asparaginase is approved for use in patients who develop allergy to other forms of asparaginase, although its ability to deplete asparagine systemically in patients with hypersensitivity has not been well elucidated. In 53 children with newly diagnosed acute lymphoblastic leukemia, we serially assessed asparagine concentrations in cerebrospinal fluid (CSF) and plasma as well as serum anti-asparaginase antibodies. All patients received native Escherichia coli (Elspar) asparaginase during induction therapy; patients received PEG asparaginase during reinductions when available, and those who developed allergy received Erwinia asparaginase. All eight patients who developed clinical evidence of allergy to asparaginase had anti-asparaginase antibodies. Among patients who had no antibodies, those who received E. coli had lower mean (+/-s.d.) CSF asparagine (0.29+/-0.63, n=9) than those who received PEG (0.77+/-0.82, n=4) (P=0.007). Results were similar for plasma asparagine. There was no situation where asparagine concentrations were more effectively depleted by PEG than by other preparations. None of the five patients who developed thrombosis had an allergy or antibodies to asparaginase at the time of the thrombosis. We conclude that asparagine concentrations were less effectively depleted by PEG than by E. coli asparaginase at the doses commonly used. The risk of thrombosis may be affected by the intensity of asparaginase exposure.

Evaluation of immunologic crossreaction of antiasparaginase antibodies in acute lymphoblastic leukemia (ALL) and lymphoma patients

To evaluate how well antibodies to one asparaginase preparation predict or correlate with antibodies to another preparation in acute lymphoblastic leukemia (ALL) and lymphoma patients who did and did not have hypersensitivity reactions during chemotherapy. In all, 24 children with newly diagnosed ALL or lymphoma, who received Escherichia coli asparaginase 10 000 IU/m(2) IM thrice weekly for nine doses as part of multiagent induction and reinduction chemotherapy, and seven monthly doses during the first 7 months of continuation treatment, were studied. Plasma samples were collected at postinduction and at postreinduction. Six of 24 patients had no overt clinical reactions (nonreacting) and received only the E. coli preparation. Of these, 18 patients who had allergic reactions were switched to Erwinia asparaginase. A total of 18 patients had an anaphylactoid reaction to Erwinia asparaginase and were switched to receive polyethylene glycol (PEG) asparaginase. Antibody levels were measured by enzyme-linked immunoadsorbent assay against all the three asparaginase preparations. At postinduction, antibodies against E. coli were higher in reacting patients (0.063+/-0.066) than in nonreacting patients (0.019+/-0.013) (P=0.03). At postreinduction, anti-Erwinia antibodies were significantly higher in reacting patients (0.431+/-0.727) than in nonreacting patients (0.018+/-0.009) (P=0.007). Anti-E. coli antibodies correlated with anti-PEG antibodies at postinduction (r=0.714, P<0.001) and at postreinduction (r=0.914, P<0.001), but did not correlate with anti-Erwinia antibodies at postinduction (r=0.119, P=0.580) and at postreinduction (r=0.078, P=0.716). The results indicate a crossreactivity between patient antibodies raised against natural E. coli and PEG asparaginase but not Erwinia asparaginase.

Effect of pentoxifylline on nitrogen balance and 3-methylhistidine excretion in parenterally fed endotoxemic rats

Pentoxifylline interrupts early gene activation for tumor necrosis factor, interleukin-1, and interleukin-6 production and improves survival from experimental sepsis. These effects can alter nitrogen loss during critical illness. To determine the dose-dependent influence of pentoxifylline on nitrogen loss, 44 male Sprague-Dawley rats (220 to 265 g) were randomized to receive parenteral nutrition only (PN), PN plus continuous infusion of Escherichia coli 026:B6 lipopolysaccharide (LPS) at 9 mg x kg(-1) x d(-1), or PN plus LPS plus a continuous infusion of pentoxifylline at either 25 (PEN25) or 100 mg x kg(-1) x d(-1) (PEN100) for 48 h. Before randomization, all animals underwent intravenous cannulation and 40 h of PN adaptation. All animals received isocaloric, isonitrogenous PN (160 kcal x kg(-1) x d(-1) and 1.0 gN x kg(-1) x d(-1)) and were kept nil per os except for water ad libitum. Administration of LPS significantly worsened nitrogen balance for all three groups compared with PN control; however, pentoxifylline only modestly improved nitrogen balance compared with LPS (206 +/- 255, -497 +/- 331, -332 +/- 329, and -310 +/- 383 mg/48hr for the PN, LPS, PEN25, and PEN100 groups, respectively; P < 0.001). Pentoxifylline did not significantly change 3-methylhistidine urinary excretion compared with LPS (573 +/- 180, 705 +/- 156, 780 +/- 326, and 683 +/- 266 microg/48 h for the PN, LPS, PEN25, and PEN100 groups, respectively, P not significant). Pentoxifylline, given in therapeutic doses after an endotoxin challenge, modestly, but not significantly, improved nitrogen balance. Urinary 3-methylhistidine excretion was not influenced by pentoxifylline. A dose-dependent effect by pentoxifylline on these markers was not evident.

Pharmacokinetics of naratriptan in adolescent subjects with a history of migraine

Naratriptan is a novel 5-HT1 agonist developed to treat acute migraine. The study objective was to characterize the pharmacokinetics of oral naratriptan in adolescent migraine patients outside a migraine attack. Subjects received a single 2.5 mg naratriptan tablet. Serial serum samples for naratriptan concentrations were collected over 24 hours. Blood pressure, pulse rate, and 12-lead ECG were recorded at baseline and at regular intervals after dosing. Seven patients--3 males and 4 females, 12 to 16 years of age--received drug and completed the study. The geometric mean and 95% confidence interval maximum concentration (Cmax) was 8.0 ng/mL (5.9-10.7), elimination half-life (t1/2) was 4.9 hours (4.5-5.4), area under the concentration-time curve (AUC) was 74.6 ng.h/mL (56.6-98.2), and apparent total clearance (Cl/F) was 558.8 mL/min (424.3-735.9). The median time to maximal concentration (tmax) was 4 hours, with a range of 1.5 to 4. Blood pressure, pulse rate, and ECG parameters did not change significantly from baseline. No serious adverse events or subject withdrawal after drug administration occurred. Oral naratriptan pharmacokinetic parameters in adolescents were similar to values reported in adults. Naratriptan doses for adolescents older than 12 years of age would be expected to be similar to adult doses.

Sequential group trial to determine gastrointestinal site of absorption and systemic exposure of azathioprine

Azathioprine (AZA) is used in the treatment of patients with refractory inflammatory bowel disease; however, its use is limited because of systemic toxicity associated with long-term use. Ileocecal delivery of AZA might be advantageous if local intestinal therapeutic effects could be provided with decreased systemic side effects. Decreased cecal systemic absorption would allow higher dosages of AZA to be administered. A two-phase study was performed to compare the systemic exposure of AZA and 6-mercaptopurine (6-MP) following administration of AZA into the stomach, jejunum, and cecum and to compare the systemic exposure to AZA and 6-MP following administration of three different dosages of AZA into the cecum. In phase I, six healthy male volunteers received three 50 mg sequential doses of AZA via an oral tube directly placed into the stomach, jejunum, and cecum, respectively. In phase II, six healthy male volunteers received three different dosages (50, 300, 600 mg of AZA) into the cecum. Plasma concentrations of AZA and 6-MP at various times were quantified and area under the plasma concentration-time curve (AUC) and mean residence time (MRT) were determined. No significant differences in the AUC of AZA were seen at the different sites. The AUC of 6-MP following administration of AZA into the jejunum (67.0 +/- 30.1 ng x hr/ml) was higher compared to the stomach (39.9 +/- 38.1 ng/hr/ml) and cecum (29.2 +/- 10.9 ng x hr/ml). Jejunal absorption was 68% higher than absorption from the stomach and 129% higher than that of the cecum. Gastric absorption was 27% higher than that of the cecum. Increased dosages given into the cecum resulted in increased AUCs of AZA and 6-MP. The AUCs of AZA following 50, 300, and 600 mg dosages were 16.9 +/- 7.4, 52.3 +/- 67.2, and 132 +/- 151 ng x hr/ml, respectively, and the AUCs of 6-MP were 22.2 +/- 14.9, 63.4 +/- 50.6, and 104 +/- 115 ng x hr/ml, respectively. Systemic exposure to 6-MP is reduced following administration of AZA into the cecum, most likely secondary to reduced absorption of 6-MP from the colon. Higher dosages of AZA presented to the cecum do result in increased systemic absorption, but may still allow more drug to be administered with less toxicity than the same dose received orally.

ELISA to evaluate plasma anti-asparaginase IgG concentrations in patients with acute lymphoblastic leukemia

The development of antibodies to asparaginase may attenuate the pharmacologic effect of asparaginase treatment, may be associated with hypersensitivity reactions, and may necessitate switching to a different commercial asparaginase preparation for current or future therapy. Thus, development of an ELISA for measurement of anti-asparaginase antibody levels is important in the clinical setting. An anti-asparaginase antibody reference was established by screening 65 plasma samples from six patients with acute lymphoblastic leukemia (ALL) who had recently developed a hypersensitivity reaction to Escherichia coli or Erwinia chrysanthemi asparaginase therapy. Twenty-one plasma samples were selected for the anti-asparaginase antibody reference pool. Five micrograms per milliliter of commercial E. coli and Erwinia asparaginase and 10 microg/ml of E. coli asparaginase conjugated with polyethylene glycol (PEG asparaginase) were found to be optimal as coating antigen concentrations. Anti-asparaginase antibody concentrations were determined using a commercial polyclonal goat anti-human IgG horseradish peroxidase conjugate. The antibody reference curves were linear in a range of absorbance from 0.1 to 1. 5 O.D. units for dilutions from 1:1600 to 1:51,200. Inter-assay coefficients of variation were 9.04, 14.7 and 13.0%, and intra-assay coefficients of variation were 1.44, 4.43 and 3.28% for antibodies against E. coli, Erwinia, and PEG L-asparaginase, respectively. The cut-off for positivity in plasma was determined as mean+2 S.D. of the optical density values for plasma from untreated healthy volunteers. Measurement of specific IgG by this ELISA allows for the evaluation of plasma anti-asparaginase antibody concentrations in patients receiving one or more of the multiple commercial L-asparaginase preparations.

Hypersensitivity or development of antibodies to asparaginase does not impact treatment outcome of childhood acute lymphoblastic leukemia

PURPOSE

Development of antibodies and hypersensitivity to asparaginase are common and may attenuate asparaginase effect. Our aim was to determine the relationship between antiasparaginase antibodies or hypersensitivity reactions and event-free survival (EFS).

PATIENTS AND METHODS

One hundred fifty-four children with acute lymphoblastic leukemia received Escherichia coli asparaginase 10,000 IU/m(2) intramuscularly three times weekly for nine doses during multiagent induction and reinduction phases and for seven monthly doses during continuation treatment. Erwinia asparaginase was used in case of clinical hypersensitivity to E coli but not for subclinical development of antibodies. Plasma antiasparaginase antibody concentrations were measured on day 29 of induction in 152 patients.

RESULTS

Antibodies were detectable in 54 patients (35.5%), of whom 30 (55.6%) exhibited hypersensitivity to asparaginase. Of the 98 patients who had no detectable antibodies, 18 (18.4%) had allergic reactions. Patients with antibodies were more likely to have a reaction than those without antibodies (P <.001). Among the 50 patients who experienced allergic reactions (including two for whom antibodies were not measured), 36 (72.0%) were subsequently given Erwinia asparaginase; seven (19.4%) reacted to this preparation. EFS did not differ among patients who did and did not have antibodies (P =.54), with 4-year EFS (+/- 1 SE) of 83% +/- 6% and 76% +/- 5%, respectively. Similarly, EFS did not differ among patients who did and did not develop allergic reactions (P =.68), with 4-year estimates of 82% +/- 6% and 78% +/- 5%, respectively.

CONCLUSION

In this setting, in which most patients with allergy were switched to another preparation, there was no adverse prognostic impact of clinical or subclinical allergy to asparaginase.

Cerebrospinal fluid asparagine concentrations after Escherichia coli asparaginase in children with acute lymphoblastic leukemia

PURPOSE

The CNS is an important sanctuary site in childhood acute lymphoblastic leukemia (ALL). CSF asparagine concentration reflects asparaginase systemic pharmacodynamics. We evaluated the time course of CSF asparagine depletion in children with ALL during and after a course of Escherichia coli asparaginase.

PATIENTS AND METHODS

Thirty-one children (24 newly diagnosed and seven at relapse) received E coli asparaginase 10,000 IU/m2 intramuscularly three times weekly for six and nine doses, respectively, as part of multiagent induction chemotherapy. CSF asparagine levels were measured before, during, and after asparaginase dosing.

RESULTS

The percentage of patients with undetectable (< 0.04 micromol/L) CSF asparagine was 3.2% (one of 31 patients) at baseline, 73.9% (17 of 23) during asparaginase therapy, and 56.3% (nine of 16) 1 to 5 days, 43.8% (seven of 16) 6 to 10 days, 20.0% (two of 10) 11 to 30 days and 0% (zero of 21) more than 30 days after asparaginase therapy. The proportion of patients with depleted CSF asparagine was higher during asparaginase therapy than at baseline (P < .001), 11 to 30 days (P = .003), and more than 30 days after asparaginase therapy (P < .001). Median CSF asparagine concentrations were 4.42 micromol/L before, less than 0.04 micromol/L during, and less than 0.04 micromol/L at 1 to 5 days, 1.63 micromol/L at 6 to 10 days, 1.70 micromol/L at 11 to 30 days, and 5.70 micromol/L at more than 30 days after asparaginase therapy, respectively. CSF depletion was more common in patients with low baseline CSF asparagine concentrations (P = .003).

CONCLUSION

CSF asparagine concentrations are depleted by conventional doses of E coli asparaginase in the majority of patients, but they rebound once asparaginase therapy is completed.

Measured energy expenditure of tube-fed patients with severe neurodevelopmental disabilities

OBJECTIVE

To determine measured resting energy expenditure (REE) of nonambulatory tube-fed patients with severe neurological neurodevelopmental disabilities.

METHODS

Twenty patients were prospectively studied. Only steady state indirect calorimetry measurements were taken. All measurements were conducted using a canopy system. Nutritional needs were met entirely by enteral feedings via a permanent ostomy.

RESULTS

REE was widely distributed from 16 kcals/kg/day to 39 kcals/kg/day. The mean REE (888+/-176 kcals/day) of the patients was significantly (p<0.01) lower than predicted as estimated by the Harris-Benedict equations (1081+/-155 kcals/day) and World Health Organization equations (1194+/-167 kcals/day). Fat-free mass (FFM) was the best parameter for predicting REE. Two predictive equations were developed that are not significantly biased and more precise (< or =15% error) than conventional predictive formulas.

CONCLUSION

Conventional formulas for estimating energy expenditure are inaccurate and generally overestimate measured energy expenditure of nonambulatory patients with severe developmental disabilities.

Anti-asparaginase antibodies following E. coli asparaginase therapy in pediatric acute lymphoblastic leukemia

Asparaginase is an effective antileukemic agent and is included in most front-line protocols for pediatric acute lymphoblastic leukemia (ALL) worldwide; however, allergic reactions to asparaginase may be dose-limiting. We evaluated plasma anti-asparaginase antibody concentrations in a cohort of children with newly diagnosed ALL, who did and who did not exhibit clinical hypersensitivity, after Escherichia coli (E. coli) asparaginase therapy. Thirty-five children who received asparaginase 10000 IU/m2 i.m. three times weekly for nine doses as part of both multiagent induction and reinduction chemotherapy, and seven monthly doses during the first 7 months of continuation treatment, were studied. Twenty-two patients experienced initial allergic reactions to asparaginase during continuation (n=20) or reinduction (n=2) phases and 13 children did not exhibit any reaction. An enzyme-linked immunosorbent assay (ELISA) was used to measure anti-asparaginase antibodies in plasma samples, diluted 1:3200, using E. coli asparaginase as the antigen. The median anti-asparaginase antibody concentration (OD at 1:3200 dilution) increased from 0.039 at induction to 0.506 at reinduction in patients who exhibited clinical hypersensitivity (P = 0.0002). By comparison, median antibody level increased from 0.011 to 0.032 OD at identical time points in patients who did not react to asparaginase (P = 0.02). Both post-induction and post-reinduction anti-asparaginase antibody levels were higher in reacting than in nonreacting patients (P = 0.004 and P = 0.01, respectively). Antibody levels were inversely related to the time elapsed between the reaction and sampling (P = 0.011). Although anti-asparaginase antibody levels increased from the post-induction plasma sample to the post-reinduction sample in 28 of 35 patients regardless of whether they exhibited clinical hypersensitivity, patients with hypersensitivity reactions had higher antibody levels than did identically treated control patients at comparable time points in therapy. Therefore, antibody analysis may be of clinical value in predicting future hypersensitivity.

Alterations in N-acetylation of 3-methylhistidine in endotoxemic parenterally fed rats

N-methylhistidine (3-meH) is endogenously released during muscle catabolism and serves as a marker of protein turnover. In rats > 85% of 3-meH is excreted in the urine as the N-acetyl derivative. It has been reported that the percent of non-acetylated 3-meH (NA-3-meH) varies minimally with stress. To further evaluate these reports we randomized 39 male Sprague-Dawley rats (157-213 g) to receive parenteral nutrition only (PN) or PN plus continuous infusion of Escherichia coli 026:B6 lipopolysaccharide at 6 (LPS-6) or 12 (LPS-12) mg.kg-1.d-1 for 48 h. All animals received isocaloric and isonitrogenous PN 24 h before and throughout the study with water ad libitum. Total 3-meH excretion was significantly increased (P < 0.05) in the LPS-6 (470 +/- 136 micrograms/48 h) and LPS-12 (557 +/- 171 micrograms/48 h) groups versus the PN (331 +/- 126 micrograms/48 h) group. NA-3-meH differed significantly between the LPS-12 (218 /+- 89 micrograms/48 h, LPS-6 (94 +/- 48 micrograms/48 h), and PN (39 +/- 12 micrograms/48 h) groups (P < 0.05). Percent NA-3-meH increased significantly from 12.7 +/- 3.9% in the PN group to 19.8 +/- 8.0 and 39.9 +/- 12.8% in the LPS-6 and LPS-12 groups, respectively (P < 0.05). No significant changes in acetyl 3-meH were found between groups. These data suggest that either saturation or inhibition of acetylation pathways occurs with increasing levels of stress. Due to the disproportionate increases in NA-3-meH and percent NA-3-meH during endotoxemia, only total 3-meH should be used as an indicator of protein turnover in rats.

Effect of sustained endotoxemia on alpha1-adrenergic responsiveness in parenterally fed rats

We investigated the effect of endotoxemia on alpha1-adrenergic receptor-mediated smooth muscle contraction as measured by mean arterial pressure (MAP) in response to incremental doses of a vasopressor. Twelve male Sprague-Dawley rats were randomized to receive parenteral nutrition alone (PN) or in combination with a continuous infusion of endotoxin (PN-LPS) for 48 hours. Incremental doses of phenylephrine were given and peak MAP response was recorded. The endotoxin group had a decreased rise in MAP with the same dose of phenylephrine compared with the control group (59 +/- 14 and 99 +/- 12 mm Hg, respectively, p<0.001). However, the baseline MAP was higher in the endotoxin group (102 +/- 18 and 71 +/- 7 mm Hg, respectively, p<0.002). The overall maximum effect was the same for both groups (161 +/- 16 and 170 +/- 8 mm Hg, respectively, p=NS). These data indicate that sustained endotoxemia does not result in desensitization of alpha1-adrenergic responsiveness. Other mechanisms are responsible for the ineffectiveness of vasopressors during advanced sepsis.

The effect of alpha-adrenergic antagonism upon nitrogen loss during endotoxemia

Sixty male Sprague-Dawley rats were randomized to receive parenteral nutrition (PN) only; PN plus continuous infusion of Escherichia coli 026:B6 lipopolysaccharide (PN + LPS) at 6 mg.kg-1.d-1; or PN plus LPS plus a continuous infusion of the alpha-adrenergic antagonist phentolamine (PN + LPS + PHEN) at 5 mg.kg-1.d-1 or 20 mg.kg-1.d-1 for 48 h. All animals received isocaloric, isonitrogenous PN. LPS significantly lowered nitrogen balance (mmol/48 h) from PN control; however, addition of PHEN substantially worsened nitrogen balance compared with LPS (14.2 +/- 3, 2.4 +/- 5.2, -1.6 +/- 4.5, -0.8 +/- 5.4, for the PN, PN + LPS, PN + LPS + PHEN5 and PN + LPS + PHEN20 groups, respectively; P < 0.0001). Urinary 3-methylhistidine/creatinine ratio (3-meH/creat) paralleled the nitrogen balance data (0.30 +/- 0.09, 0.45 +/- 0.12, 0.51 +/- 0.14, 0.60 +/- 0.12, respectively; P < 0.0001). The high-dose PHEN resulted in 82 +/- 9% blockade. To ascertain if any beneficial effect upon body protein loss is achieved during severe stress, 30 rats were given PN + LPS at 12 mg.kg-1.d-1 or PN + LPS12 + PHEN20. These data showed similar changes in nitrogen balance and 3-methylhistidine/creatinine with the use of PHEN during severe endotoxemia. alpha-adrenergic antagonism with PHEN worsens body protein loss as measured by nitrogen balance and 3-methylhistidine/creatinine in PN-fed endotoxemic rats.

Recovery from ischemic acute renal failure is improved with enteral compared with parenteral nutrition

OBJECTIVE

To compare measurements of renal function after acute ischemic renal failure in rats fed enterally or parenterally.

DESIGN

Prospective, randomized, animal trial.

SETTING

University research laboratory.

SUBJECTS

Male Sprague-Dawley rats (n = 21).

INTERVENTIONS

Animals were randomized to receive isocaloric (160 nonprotein kcal/kg/day), or isonitrogenous (1.4 g of nitrogen/kg/day [100 mmol/kg/day]) enteral (n = 10), or parenteral nutrition (n = 11) through either a gastrostomy tube or a catheter placed in the jugular vein. After the animals received 7 days of assigned feedings, baseline blood samples were collected. A right nephrectomy and 45-min left renal pedicle occlusion were then performed. One hour after the ischemic injury, assigned feedings were resumed and continued for 3 days. After ischemic injury, daily blood samples were obtained and 24-hr urine collections were performed. On day 11, animals were killed and the kidney was harvested and fixed for subsequent microscopic examination.

MEASUREMENTS AND MAIN RESULTS

Urine was analyzed for concentrations of total urea nitrogen, creatinine, protein, and calcium. Serum was analyzed for creatinine and urea nitrogen concentrations. Fixed kidney sections were examined for mitotic figures, tubular calcifications, and casts using light microscopy by an investigator blinded to the nutritional regimen. Data are presented as mean +/- SD or median (range). Percent increase in creatinine clearance from the nadir on day 9 to day 11 was approximately 2.5-fold greater in the enteral compared with the parenteral nutrition group (490 +/- 221% vs. 208 +/- 130%; p = .003). Histologic evaluation demonstrated greater dystrophic tubular calcifications per ten high-power fields in the parenteral compared with the enteral nutrition group (50 [four to 85] vs. three [0 to 37]; p = .001). No differences in urine calcium concentration or 24-hr calcium excretion were seen.

CONCLUSION

Rats given continuous enteral nutrition 7 days before and for 3 days after ischemic acute renal failure have improved renal function compared with rats given parenteral nutrition.

Impact of a pharmacist-based consult service on nutritional rehabilitation of nonambulatory patients with severe developmental disabilities

A pharmacist consult service was developed to evaluate the appropriateness of enteral feeding through a permanent ostomy in 24 nonambulatory patients with severe developmental disabilities. Several problems with enteral nutrition were identified. Policies to improve them were instituted, and several educational presentations were made. Pharmacists' actions were implemented, including assessment of energy needs by indirect calorimetry and rearrangement of enteral feeding schedules to achieve optimal nutrition support and pharmacotherapy administration. By the fourth month of the consult service, body weight in these patients increased from 101 +/- 6% of baseline to 109 +/- 7% (p<0.05). Weight continued to increase through the seventh month of the consult service to 116 +/- 12% of baseline (p<0.0001). Measured resting energy expenditure for the group was 889 +/- 170 kcal/day compared with the predicted 1055 +/- 163 kcal/day.

Octreotide and potassium homeostasis

Somatostatin infusion causes hyperkalemia in healthy subjects and in some animal models. The purpose of this investigation was to determine what effect octreotide has on potassium homeostasis during serious illness and if there is a dose-response relationship. Sixty-six male Sprague-Dawley rats (185-225 g) were randomized to receive parenteral nutrition (PN) only, PN plus continuous infusion of Escherichia coli lipopolysaccharide (LPS), or PN plus LPS plus octreotide 10, 100, or 1000 micrograms/kg/day for 48 hours. Before randomization all animals received isocaloric, isonitrogenous, isokalemic PN. A 24-hour urine was collected and a blood sample was taken at the end of the study immediately before euthanization. Data were analyzed by ANOVA and Duncan's multiple range test. Nonhemolyzed serum samples from 50 rats were available for study. Serum potassium concentrations were in the normal range for rats and did not differ significantly among the groups: 5.97 +/- 0.86, 5.96 +/- 1.58, 5.78 +/- 1.48, 5.79 +/- 1.67, 5.35 +/- 0.78 mEq/L, respectively. No differences among groups were found for fractional excretion of potassium or serum creatinine concentration. Octreotide administration in escalating dosages does not cause hyperkalemia in endotoxemic rats given intravenous potassium at a constant rate by PN.

Dose-dependent effect of octreotide on nitrogen retention and glucose homeostasis in response to endotoxemia in parenterally fed rats

OBJECTIVE

This study compared the effect of different doses of octreotide on glucose and protein homeostasis in rats receiving concomitant lipopolysaccharide and parenteral nutrition infusions.

METHODS

Sixty-six male Sprague Dawley rats (185 to 220 g) were randomized to receive parenteral nutrition only (PN), PN plus continuous infusion of Escherichia coli 026:B6 lipopolysaccharide at 6 mg/kg/day (LPS), PN plus LPS plus octreotide at 10 micrograms/kg/day (LPS + Oct 10), 100 micrograms/kg/day (LPS + Oct 100), or 1000 micrograms/kg/day (LPS + Oct 1000) for 48 hours. Prior to randomization all animals received isocaloric and isonitrogenous PN (170 kcal/kg/day as glucose and 1.1 g N/kg/day) and were kept nil per os except for water ad libitum. Nitrogen balance, urinary 3-methylhistidine/creatinine ratio, serum glucose concentration, and incidence of glycosuria were compared between groups. Serum urea nitrogen (SUN) changes were incorporated into the cumulative 48 hour nitrogen balance. ANOVA, Duncan's multiple range test, and Fisher's Exact Test were used for statistical analysis.

RESULTS

Nitrogen balance (mg/48 hours) was significantly lower in all four groups receiving LPS +/- Oct when compared to the control group receiving PN alone. SUN (mg/dL) was significantly higher in all four groups receiving LPS +/- Oct when compared to control. There were no statistically significant differences in nitrogen balance or SUN among the four groups receiving LPS +/- Oct. The ratio of urinary 3-methylhistidine/ creatinine was significantly higher in the LPS + Oct 1000 group compared to the PN group (0.77 +/- 0.37 vs. 0.42 +/- 0.24, p < 0.05). Serum glucose concentrations and incidence of glycosuria among the five groups were not significantly different.

CONCLUSIONS

Endotoxin significantly reduces nitrogen balance compared to controls fed PN. Octreotide does not significantly improve nitrogen retention or glucose homeostasis in endotoxemic parenterally fed rats.

Disposition of didanosine in HIV-seropositive patients with normal renal function or chronic renal failure: influence of hemodialysis and continuous ambulatory peritoneal dialysis

OBJECTIVE

To evaluate the pharmacokinetics of didanosine in patients with normal kidney function or chronic kidney failure.

METHODS

Three groups of patients with human immunodeficiency virus (HIV) infection were studied: group I, six men with normal kidney function (creatinine clearance > 90 ml/min/1.73 m2); group II, six men with chronic renal failure maintained on continuous ambulatory peritoneal dialysis (CAPD); and group III, four men and two women with chronic renal failure receiving hemodialysis three times a week. A 300 mg dose of didanosine was administered orally and intravenously according to a two-period randomized crossover design. Patients in group III were studied between hemodialysis sessions during the crossover periods. In addition, patients in group III were studied in a third period after administration of a 300 mg oral dose of didanosine 4 hours before hemodialysis.

RESULTS

After intravenous administration in group I, the mean (+/-SD) total clearance (CLT) was 13.0 +/- 1.6 ml/min/kg and the elimination half-life (t 1/2) was 1.56 +/- 0.43 hour. In groups II and III, the CLT decreased significantly to 3.4 +/- 1.2 and 3.2 +/- 1.2 ml/min/kg, respectively, whereas the t1/2 increased to 3.60 +/- 0.82 hours and 3.11 +/- 0.88 hours, respectively. The absolute bioavailability of didanosine in groups I, II, and III was 42% +/- 12%, 52% +/- 6%, and 38% +/- 11%, respectively, and did not differ significantly. CAPD had little effect on the removal of didanosine, whereas approximately 30% of the drug present in the body at the start of dialysis was eliminated by an average 3-hour dialysis session.

CONCLUSION

The clearance of didanosine is impaired in patients with chronic renal failure. To compensate, the dose and schedule of administration should be adjusted. It is recommended that one-fourth of the total daily dose of didanosine be administered once a day in this patient population.

Pharmacokinetics of ondansetron in patients with hepatic insufficiency

Ondansetron is primarily eliminated via hepatic metabolism; thus, liver disease may affect its clearance. The pharmacokinetics of ondansetron in patients with different degrees of hepatic insufficiency (N = 12 with hepatic impairment, as categorized by Pugh's classification method) were assessed and the results compared with results for age- and gender-matched control subjects with normal liver function (n = 12). A secondary objective was to correlate the Pugh method of assessing hepatic impairment and quantitative metabolic markers used to assess hepatic function (antipyrine clearance and indocyanine green clearance) with changes in the pharmacokinetics of ondansetron. This was an open-label study in which 8 mg ondansetron was given orally and intravenously, following a randomized crossover design. Clearance of ondansetron was lower among patients with hepatic impairment that control subjects. After a single, oral dose of ondansetron, mean absolute bioavailability increased markedly with increased hepatic insufficiency (approaching 100% in the group with severe hepatic impairment versus 66% for control subjects). These data suggest that there is a reduced first-pass effect in patients with liver disease resulting in a higher AUC0-infinity. A correlation existed between clearance of ondansetron and decreased antipyrine clearance; a smaller correlation existed between ondansetron clearance and indocyanine green clearance. Mean percent of ondansetron bound to plasma proteins was significantly lower in patients with liver disease than in control subjects. None of the patients experienced any severe adverse reactions attributed to ondansetron. A reduction in the clearance of ondansetron is associated with increasing degrees of hepatic insufficiency; therefore, patients with severe hepatic impairment (Pugh score of > 9) should have their daily dose of ondansetron limited to 8 mg (or 0.15 mg/kg).

Comparison of quantitative methods to assess hepatic function: Pugh's classification, indocyanine green, antipyrine, and dextromethorphan

STUDY OBJECTIVES

To compare three quantitative metabolic markers used to assess hepatic function, indocyanine green (ICG), a high-extraction marker; antipyrine, a low-extraction marker; and dextromethorphan, a P-450IID6 marker, with the clinically used Pugh's classification.

DESIGN

Comparison of 12 healthy controls with 12 age- and sex-matched patients with different degrees of liver disease.

SETTING

Research center in a university-affiliated teaching hospital.

PATIENTS

The 12 patients had different degrees of liver disease: 4 mild (Pugh's score 6 or 7); 4 moderate (Pugh's score 8 or 9); and 4 severe (Pugh's score > or = 10). Each level had an equal number of men and women subjects.

MEASUREMENTS AND MAIN RESULTS

Clearance of ICG detected mild alterations in hepatic function as efficiently as it did for moderate and severe impairment, but it lacked the specificity to distinguish among the classification groups. In contrast, antipyrine was effective in identifying moderate and severe hepatic impairment; however, its clearance was not reduced in mild liver disease. Pugh's classification appears to be a clinically useful method of assessing the global degree of hepatic impairment in patients with chronic disease, and there was a significant correlation between it and antipyrine clearance (r = 0.67, p = 0.0003) and ICG clearance (r = 0.86, p = 0.0001). Four of eight patients with a Pugh's score greater than 8 had a dextromethorphan metabolic ratio expression reflective of a poor metabolizer phenotype based on 0- to 4-hour urine collection, but only two of those eight patients were classified as poor metabolizers based on 4- to 12-hour urine collection. These percentages of poor metabolizers are substantially higher than for historical controls (8.5-10.4%) and most likely reflect a decrease in the P-450IID6 functional ability with progression of liver disease. However, due to small sample size and lack of knowledge of the patients' genotypes, these data are only suggestive.

CONCLUSION

Pugh's classification appears to be a reliable indicator of the degree of chronic liver disease and could be employed as a drug development research classification tool; however, it does not replace quantitative metabolic markers, especially isozyme-specific markers.

A dose-response study of orally administered torsemide in patients with ascites due to cirrhosis

BACKGROUND

This study evaluated the dose-response relationship of torsemide, the first pyridine-sulphonylurea loop diuretic, in patients with ascites due to cirrhosis.

METHODS

During a 13-day hospitalization period, 17 patients received single, oral doses of 5 mg, 10 mg, or 20 mg of torsemide or placebo in a randomized, double-blind, crossover fashion. All the patients received a constant dose of spironolactone concomitantly beginning at least 7 days before the study. Electrolyte excretion and urine volume were measured for 24 h after each dose. Body weight was measured before, and 24 h after each dose.

RESULTS

Torsemide was effective in producing statistically significant, dose-related increases in urinary sodium and chloride excretion, with little effect on potassium or magnesium excretion. Urine volume increased and body weight decreased in a dose-related manner.

CONCLUSION

Torsemide increased sodium excretion substantially in patients with cirrhosis and ascites who were receiving spironolactone.

Ondansetron: a novel antiemetic agent

Ondansetron hydrochloride is a new serotonin receptor antagonist that is effective in preventing emesis associated with cancer chemotherapy. The antiemetic effect appears to be exerted through a peripheral vagal blocking within the gastrointestinal tract, as well as an inhibitory effect within the chemoreceptor trigger zone (CTZ). Plasma concentrations of ondansetron peak 1 hour after an oral dose, and the tablet has an absolute bioavailability of 59%. Ondansetron undergoes extensive hepatic oxidative metabolism in the liver. The half-life of ondansetron is 3.5 hours in healthy volunteers; elderly patients have a slightly reduced clearance, and pediatric patients have increased clearance. Although less than 10% of ondansetron is recovered unchanged in the urine, most metabolites are eliminated by this route. The recommended dose of ondansetron is 0.15 mg/kg for three doses on the day of chemotherapy (30 minutes before chemotherapy and 4 and 8 hours afterward). An alternative regimen includes a single-day dose of 32 mg IV in adult patients before chemotherapy. The efficacy of ondansetron therapy for delayed emesis has not been determined. Ondansetron has proven to be appropriate as a single agent or as an addition to standard antiemetic therapy (ie, corticosteroids, benzodiazepines, neurotransmitter blockers) in preventing and treating acute chemotherapy-induced emesis (CIE). Initial results of clinical trials in prevention of radiotherapy-induced emesis and anesthesia-induced emesis appear positive. Ondansetron is well tolerated, with few adverse events (eg, headache, sedation).

Stability of ondansetron hydrochloride injection in extemporaneously prepared oral solutions

The stability of ondansetron hydrochloride in extemporaneously prepared oral solutions containing orange juice, cola, or cherry syrup was determined. Solutions were prepared by adding ondansetron hydrochloride to orange juice, cola, or cherry syrup to produce ondansetron concentrations of 0.267 and 0.067 mg/mL in orange juice or cola and 0.533 mg/mL in cherry syrup. The ondansetron concentration in orange juice and cola solutions was assayed at the time of preparation and at 30 minutes and one hour. The cherry syrup solution was stored at both 3-5 and 25-27 degrees C, with the ondansetron concentration being determined at the time of preparation and daily for seven days. All the solutions were prepared in triplicate. Ondansetron concentrations were measured by stability-indicating high-performance liquid chromatography. At each time interval, the mean ondansetron concentration remained > or = 97% of the initial measurement for all solutions. The appearance and color of the solutions did not change. Ondansetron hydrochloride was stable for at least one hour in orange juice or cola and at least seven days in cherry syrup.

Influence of gastrointestinal site of drug delivery on the absorption characteristics of ranitidine

The absorption characteristics of ranitidine after delivery to three locations in the gastrointestinal tract were compared in an open-label study of eight healthy males. Subjects received ranitidine HCl (150 mg) for injection via a nasoenteric tube directly into their stomach, jejunum, or cecum sequentially in three separate periods (24 hr apart). Plasma samples were collected at periodic time intervals for 12 hr following each dosing and analyzed for ranitidine concentration by high-pressure liquid chromatography. Mean concentrations following cecal dosing were lower (P less than 0.05) than concentrations following gastric or jejunal dosing at each sampling time except baseline. Mean concentrations following gastric and jejunal dosing were similar except at 2 hr (gastric greater than jejunal). Mean pharmacokinetic parameters for cecal administration were different (P less than 0.05) from either the gastric or the jejunal periods with the exception of Tmax. There was no difference in any pharmacokinetic parameter after gastric or jejunal dosing. The relative bioavailability after cecal administration was less than 15% of that observed after administration into the stomach or jejunum. Additionally, Wagner-Nelson analysis indicated that the rate of ranitidine absorption was much slower following cecal administration than after gastric or jejunal dosing. Two plasma concentration peaks were observed in three of eight subjects after gastric dosing, in eight of eight subjects after jejunal dosing, and in zero of eight subjects after cecal dosing. These data demonstrate that the absorption profile of ranitidine is equivalent, in extent and duration, after delivery to the stomach or jejunum, while absorption from the cecum is significantly less.(ABSTRACT TRUNCATED AT 250 WORDS)

Ranitidine does not alter adinazolam pharmacokinetics or pharmacodynamics

Adinazolam is a triazolobenzodiazepine with anxiolytic and antidepressant activity. Adinazolam is metabolized extensively; the major metabolite, N-desmethyladinazolam (NDMAD), possesses significant pharmacologic activity. NDMAD is eliminated predominantly by renal excretion. Ranitidine, a histamine H2-receptor antagonist, is also excreted renally and may compete with NDMAD for renal secretion. The purpose of this study was to examine the effect of ranitidine on the pharmacokinetics and pharmacodynamics of adinazolam and NDMAD. In a randomized, cross-over study, 12 healthy male volunteers received 300 mg of ranitidine orally followed by 30 mg of adinazolam 1 hour later (treatment A), or adinazolam alone (treatment B). Pharmacodynamic alterations were assessed using card sorting, digit-symbol substitution, and short-term memory tests. Venous blood samples were obtained over 24 hours for analysis of adinazolam and NDMAD by high-performance liquid chromatography. Urine samples also were collected and analyzed for NDMAD. No significant difference in adinazolam oral clearance (1,149 vs. 1,135 ml/hr/kg) was noted between treatments (A vs. B, respectively). Furthermore, the renal clearance of NDMAD (196 vs. 198 ml/min) and the cumulative urinary excretion of NDMAD (% dose; 61.2 vs. 62.3) were not significantly different. Repeated-measures analysis of variance indicated no significant differences in psychomotor performance or short-term memory between treatments. Results suggest that ranitidine has no effect on adinazolam disposition, NDMAD renal clearance, or the central nervous system effects mediated by the drug.

Pharmacokinetics of cefepime in patients undergoing continuous ambulatory peritoneal dialysis

The pharmacokinetics of cefepime were studied in 10 male patients receiving continuous ambulatory peritoneal dialysis therapy. Five patients received a single 1,000-mg dose and the other five received a single 2,000-mg dose; all doses were given as 30-min intravenous infusions. Serial plasma, urine, and peritoneal dialysate samples were collected; and the concentrations of cefepime in these fluids were measured over 72 h by using a high-performance liquid chromatographic assay with UV detection. Pharmacokinetic parameters were calculated by noncompartmental methods. The peak concentrations in plasma and the areas under the plasma concentration-versus-time curve for the 2,000-mg dose group were twice as high as those observed for the 1,000-mg dose group. The elimination half-life of cefepime was about 18 h and was independent of the dose. The steady-state volume of distribution was about 22 liters, and values for the 1,000- and 2,000-mg doses were not significantly different. The values for total body clearance and peritoneal dialysis clearance were about 15 and 4 ml/min, respectively. No dose dependency was observed for the clearance estimates. Over the 72-h sampling period, about 26% of the dose was excreted intact into the peritoneal dialysis fluid. For 48 h postdose, mean concentrations of cefepime in dialysate at the end of each dialysis interval exceeded the reported MICs for 90% of the isolates (MIC90s) for bacteria which commonly cause peritonitis resulting from continuous peritoneal dialysis. A parenteral dose of 1,000 or 2,000 mg of cefepime every 48 h would maintain the antibiotic levels in plasma and peritoneal fluid above the MIC90s for the most susceptible bacteria for the treatment of systemic and intraperitoneal infections [corrected].

Stability of ondansetron in large-volume parenteral solutions

OBJECTIVE

To determine the stability of ondansetron hydrochloride in large-volume parenteral solutions under four storage and time-period conditions.

DESIGN/METHOD

Ondansetron was added to each of the following commercially available solutions to make final concentrations of approximately 24 and 96 micrograms/mL: NaCl 0.9%, D5W, and lactated Ringer's solution.

SETTING

University analytical laboratory.

MAIN OUTCOME MEASURES

Each solution was studied at both concentrations under the following conditions: (1) 1 day refrigerated, 2 days room temperature; (2) 7 days refrigerated, 2 days room temperature; (3) 14 days refrigerated, 2 days room temperature; and (4) 14 days room temperature. All solutions were exposed to fluorescent light when under room temperature conditions and were studied in triplicate. Ondansetron concentrations of samples were obtained periodically throughout each storage/time condition via a specific, stability-indicating HPLC method.

RESULTS

A clinically significant loss of concentration was defined as greater than 10 percent decrease from the initial concentration. In all solutions and at both concentrations studied, the mean ondansetron concentration was greater than or equal to 90 percent under all storage and time conditions.

CONCLUSIONS

Ondansetron can be stored and administered in these solutions without loss of potency.

Comparison of verapamil, diltiazem, and labetalol on the bioavailability and metabolism of imipramine

Twelve healthy male subjects completed this randomized, placebo controlled, four-period crossover trial to determine the effect of verapamil, diltiazem, and labetalol on the bioavailability and metabolism of imipramine. Subjects received a 7-day course of one of four treatments; verapamil (120 mg every 8 hr), diltiazem (90 mg every 8 hr), labetalol (200 mg every 12 hr), or placebo (every 12 hr) during each study period. Imipramine (100 mg) was administered orally on the morning of day 4 of each study period. Plasma and urine samples were collected periodically over the ensuing 96 hours. Samples were assayed by HPLC for imipramine, desipramine, 2-hydroxyimipramine, and 2-hydroxydesipramine. Verapamil, diltiazem, and labetalol increased imipramine area under the plasma concentration time curve (relative bioavailability) as compared with placebo by 15%, 30%, and 53%, respectively. Verapamil and diltiazem did not demonstrate consistent changes in the formation of the measured metabolites. Labetalol caused a significant decrease in the amount of imipramine metabolized to 2-hydroxyimipramine (mean decrease: 22%) and from desipramine to 2-hydroxydesipramine (mean decrease: 8%). The molar ratios of plasma AUC of 2-hydroxyimipramine and 2-hydroxydesipramine to the parent compounds were significantly decreased. Since these metabolic processes are dependent on the cytochrome P450IID6 isozyme, these data suggest that labetalol decreases the oral clearance of imipramine by inhibiting this system. All three of these commonly used agents decreased the oral clearance of imipramine. These drug interactions could lead to elevated imipramine concentrations and have the potential for clinically important adverse events.

The effect of aldose reductase inhibition and dietary protein restriction on renal function in experimental diabetes mellitus

The effects of aldose reductase inhibition on renal function in hyperphagic diabetic rats were examined at 3 months. To prevent a high dietary protein intake from influencing renal function, protein intake in the diabetic animals was reduced to that of nondiabetic animals. To determine the influence of renal prostaglandins, clearance studies were performed before and after indomethacin infusion. Experiments were performed in uninephrectomized sorbinil-treated and -untreated streptozocin-diabetic and sorbinil-treated and -untreated control rats. Despite normalization of protein intake, the mean value of the insulin clearance (CIn, mL/min/100 g BW) was 83% greater in the untreated diabetic rats when compared to the untreated control rats (1.06 +/- 0.15 vs. 0.58 +/- 0.07; p less than 0.05). In contrast, the mean value of the CIn in the sorbinil-treated diabetic rats was significantly less than that in the untreated diabetic rats and only 38% greater than the mean value in the sorbinil-treated control rats (0.84 +/- 0.17 vs. 0.61 +/- 0.05; p less than 0.05). In a similar fashion, without sorbinil treatment the mean value of renal blood flow (RBF, mL/min/100 g BW) was greater in the diabetic than the control rats (6.58 +/- 2.03 vs. 3.70 +/- 0.68; p less than 0.05); whereas the mean values of RBF in the sorbinil-treated diabetic and control rats were not significantly different (4.75 +/- 0.73 vs. 4.17 +/- 0.64; NS). Indomethacin infusion failed to cause changes in the CIn and RBF in any group of animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of the pharmacokinetic interaction between diazepam and ACC-9653 (a phenytoin prodrug) in healthy male volunteers

The protein binding and pharmacokinetics of diazepam, ACC-9653 (a phenytoin prodrug), and phenytoin were evaluated in nine healthy male volunteers following administration of diazepam and ACC-9653, alone or concomitantly, in a randomized crossover design. No significant differences were observed in the fraction unbound or pharmacokinetic parameters of ACC-9653, phenytoin, or diazepam when ACC-9653 was administered alone compared to concomitant administration with diazepam. The phenytoin fraction unbound increased significantly with increased concentrations of ACC-9653, indicating displacement of phenytoin from its binding sites by ACC-9653. ACC-9653 also demonstrated concentration dependent binding. The lack of a significant pharmacokinetic drug interaction between ACC-9653 and diazepam suggests that these drugs may be safely administered together, although this conclusion should be confirmed in the intended patient population.

In vitro evaluation of the stability of ranitidine hydrochloride in total parenteral nutrient mixtures

The stability of ranitidine hydrochloride in various total parenteral nutrient (TPN) solutions was studied, as well as the effect of ranitidine on the stability of lipid emulsion and amino acids in these solutions. Ranitidine hydrochloride 25 mg/mL was added to each of the following mixtures to make final concentrations of approximately 50 and 100 mg/L: (1) TPN solution containing 4.5% amino acids, 22.7% dextrose, and electrolytes; (2) 10% lipid emulsion; (3) TPN solution containing 3.7% amino acids, 18.5% dextrose, 3.7% lipid emulsion, and electrolytes (all-in-one mixture); and (4) 0.9% sodium chloride injection. Mixtures were tested at room temperature and at 4 degrees C and were either protected from or exposed to fluorescent light. Sampling was done at 0, 12, 24, 36, and 48 hours, and the ranitidine concentration was determined by high-performance liquid chromatography. Samples were also analyzed for lipid particle size distribution and for amino acid content. At 48 hours, the all-in-one mixtures retained 86.0% to 91.4% of the initial ranitidine concentration. With one exception (ranitidine 50 mg/L in 0.9% sodium chloride injection, stored at room temperature and not protected from light), all other solutions retained at least 90% of the initial concentration at 48 hours. No visible changes in color and minimal changes in pH values were noted. There were no important changes in lipid particle-size distribution; 96% of all particles counted from any mixture were smaller than 1.44 microns in diameter at 48 hours. Ranitidine did not have an effect on amino acid concentrations in these mixtures.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation of delayed peak concentration with infusion-site irritation following diazepam administration

Diazepam 10 mg/2 mL iv was administered undiluted over five minutes to nine healthy men on two separate occasions. The infusion site was evaluated before and after each infusion by subject assessment of pain on a severity scale of zero (none) to ten (most). Blood samples were collected at 0, 5, 20, 30, 45, and 60 minutes, and periodically for 72 hours postinfusion. Diazepam plasma concentrations were determined by HPLC. Concentrations at five minutes (end of infusion) ranged from 0 to 889 ng/mL. Maximum plasma concentration (Cmax) was observed at 5 minutes for 10 treatments, at 20 minutes for 7 treatments, and at 30 minutes for 1 treatment. The observed Cmax ranged from 221 to 889 ng/mL. When time to reach peak plasma concentration (tmax) was 5 minutes, the Cmax was significantly greater than when tmax was 20 minutes (670 +/- 87 vs. 267 +/- 40 ng/mL, p less than 0.005). The area under the curve did not differ significantly between these two groups. The pain score at the end of infusion ranged from zero to five and was inversely related to the concentration at five minutes (r2 = 0.45, p = 0.002). The association between venous irritation, a low plasma concentration at the end of the infusion, and a delayed Cmax suggests that diazepam precipitated in the vein.

Omeprazole: a novel antisecretory agent for the treatment of acid-peptic disorders

Omeprazole represents the first agent of a unique class of acid inhibitory drugs, the proton pump inhibitors. Omeprazole inhibits basal gastric acid secretion, as well as gastrin-, histamine-, or pentagastrin-stimulated secretion, which results in decreased gastric acidity, decreased gastric acid output, and decreased gastric volume. Omeprazole is acid labile, necessitating its oral administration in an enteric-coated formulation. Bioavailability appears to be dose-dependent, with more drug being absorbed with increasing dosage as well as after repeated dosing. This is probably secondary to decreased gastric acidity and, therefore, less degradation of the administered drug. Despite its relatively short half-life (1-2 h), omeprazole's pharmacologic action is prolonged. Clinical trials have shown omeprazole to be at least as effective as histamine2-receptor antagonists in the treatment of gastric ulcers, duodenal ulcers, gastroesophageal reflux, and Zollinger-Ellison syndrome. Adverse reactions have been minimal. Omeprazole has been approved by the Food and Drug Administration for short-term therapy of severe erosive esophagitis, poorly responsive symptomatic gastroesophageal reflux disease, and long-term management of Zollinger-Ellison syndrome.

Efficacy of tube feeding in supplying energy requirements of hospitalized patients

During a 6-week period, all adult patients in a university hospital receiving ready-to-feed nasoenteric tube feeding formula were prospectively studied. The study objective was to determine each patient's caloric intake from tube feeding relative to their energy needs and to identify factors causing decreased feeding intake. Each of 35 patients was visited at least once daily to determine their volumetric intake of tube feeding formula. Daily review of patient care records and nursing interviews were used to identify interruptions in therapy. Patient's basal energy expenditures (BEE) were calculated using the Harris-Benedict equation. Calorie goals were set by members of the Nutrition Support Service or clinical dietitians. Intakes averaged 1095 +/- 41 Kcal (SEM) per day or 61% of their mean calorie goal of 1791 +/- 41 Kcal. Mean daily calorie intake was statistically different (p less than 0.05) from mean energy goal on patient study days 1 through 5, 7, and 8. Only 16 of the 35 patients achieved an intake of 100% of their energy goal on any day of therapy. Calorie goals averaged 1.4 times BEE. Mean daily calorie intake did not exceed BEE until study day 10. Eighteen % of potential feeding time was lost due to temporary feeding interruptions; primarily inadvertent extubation (4.6%), gastrointestinal intolerance (4.7%), medical procedures requiring discontinuation of feeding (2.8%), and feeding tube positioning difficulties (1.5%). In addition, physicians ordered only 75% of calculated energy goals. These data indicate that tube feeding therapy, when provided under usual hospital conditions, does not meet patient's energy requirements.

Influence of the rate of infusion on cyclosporine nephrotoxicity in the rat

The effect of the rate of infusion of single and multiple doses of cyclosporine (CsA) on renal function was evaluated in Sprague-Dawley rats. CsA was dissolved in cremophore (Crem) or Tween 80 (Tween) and infused over consecutive 10-min periods at doses of 10, 20, 30 and 40 mg/kg. CsA-Crem and CsA-Tween produced similar and progressive changes in MAP, RBF, and RVR. By the end of the infusion, the mean values (% of control) of MAP (122 +/- 16% and 131 +/- 22%), RBF (56 +/- 11% and 66 +/- 20%), and RVR (222 +/- 38% and 232 +/- 134%) were significantly different from their respective preinfusion values. Infusion of Crem alone resulted in renal vasodilation at low doses and renal vasoconstriction at high doses. Vasoconstriction was not produced by infusion of Tween alone. In addition, animals were treated with vehicle alone (Gp 1), CsA 10 mg/kg/day by injection (Gp 2), or CsA 20 mg/kg/day by i.v. infusion over 4 hr (Gp 3), and were studied at 1 week. Systemic toxicity was greater with the 4-hr infusion as judged by an increase in MAP. The mean values of MAP were 107 +/- 8 (Gp 1), 101 +/- 13 (Gp 2), and 135 +/- 5 mm Hg (Gp 3; p less than 0.05). However, renal function was less severely affected with the 4-hr infusion. The mean values of CIn were 434 +/- 99 (Gp 1), 298 +/- 101 (Gp 2; p less than 0.05), and 425 +/- 114 microL/min/100 g BW (Gp 3); and the mean values for RBF were 2.72 +/- 0.74 (Gp 1), 2.08 +/- 0.17 (Gp 2; p less than 0.05), and 3.35 +/- 0.61 mL/min/100 g BW (Gp 3), respectively. Microangiograms showed marked abnormalities in the intrarenal perfusion pattern in the rats injected with CsA, 10 mg/kg BW. In rats infused over 4 hr with CsA, 20 mg/kg BW, the microangiographic pattern was normal. These studies demonstrate that the acute hemodynamic effects of CsA are directly related to the rate of infusion. Furthermore, the renal toxicity which follows repetitive injection of CsA can be minimized or avoided by administering CsA as a slow infusion. In addition to the total dose administered, the rate of infusion is an important determinant of nephrotoxicity.

Protective effect of prostacyclin on postischemic acute renal failure in the rat

Infusion of prostacyclin (PGI2) reportedly attenuates renal ischemic injury in the dog and the rat. In the dog, PGI2 is a potent renal vasodilator; in the rat a direct action on the renal vasculature is not always apparent. To determine whether or not the protective effect of PGI2 on postischemic ARF was hemodynamically mediated, studies were performed in uninephrectomized Sprague-Dawley rats before and after a 40 minute period of complete renal artery occlusion. In response to the preischemic infusion of PGI2 for 30 minutes at 160 ng/kg body wt/min i.v. (N = 7), MAP and RBF fell to 86 +/- 7% (P less than 0.0001) and 84 +/- 9% (P less than 0.05) of baseline values, respectively. RVR initially declined to 81 +/- 9% of baseline values (P less than 0.025) but returned to 102 +/- 13% of baseline values prior to the period of ischemia. Following the period of ischemia, reflow of blood in the rats receiving PGI2 was delayed when compared to rats not receiving PGI2 (N = 7). RBF returned to only 76 +/- 19% of the initial values in PGI2-treated rats (P less than 0.01) but to 90 +/- 12% of the initial values in rats receiving buffer alone (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Use of plasma somatomedin-C/insulin-like growth factor I measurements to monitor the response to nutritional repletion in malnourished patients

Changes in plasma somatomedia-C/insulin-like growth factor I (Sm-C/IGF-I) concentrations are a sensitive indicator of the anabolic response of normal human volunteers to alterations in nutritional intake. To determine if measurement of this peptide could be used to monitor the response to nutritional repletion in malnourished patients, six patients were studied while receiving nutritional support for periods of 10-16 days. Plasma Sm-C/IGF-I increased from a mean basal level of 0.67 +/- 0.15 U/ml (+/-1 SD) to a peak of 1.80 +/- 0.44 U/ml on day 10, then declined to a concentration of 1.28 +/- 0.49 U/ml by day 16. All patients entered positive nitrogen balance by day 2 and nitrogen accretion continued throughout the study. Changes in serum concentrations of prealbumin, transferrin, and retinol-binding protein were compared to changes in Sm-C/IGF-I during nutritional support. Prealbumin increased to a posttreatment mean of 121 +/- 23% of control by the end of the study (p greater than 0.05, NS). Likewise, there was minimal change in retinol-binding protein, a peak value of 118 +/- 21% of control being reached by day 12 of treatment (p greater than 0.05, NS). Transferrin also showed minimal change, increasing to a mean value of 110% +/- 13% of control by day 12 (p greater than 0.05, NS). Measurement of plasma Sm-C/IGF-I concentrations appears to be a much more sensitive index of acute directional changes in nutritional status than other plasma proteins commonly used to monitor nutritional responses. The increase of Sm-C/IGF-I correlated temporally with entry into positive nitrogen balance.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of intravenous glucose and fat calories on host and tumor growth

This study was undertaken to determine if the proportions of intravenous carbohydrate and fat calories influence the relative growth of a Walker 256 carcinosarcoma and its host. Rats injected intraperitoneally with Walker 256 carcinosarcoma cells were randomized into three total parenteral nutrition (TPN) groups, G/AA in which glucose provided all nonprotein calories, G/F/AA in which the nonprotein calories were 20% fat and 80% glucose, and F/AA in which all nonprotein calories were from fat. Except for the caloric source, TPN for each group was identical. A fourth group was sham operated, fed rat food, and was not given TPN. On the 6th day after inoculation, the tumor in each rat showed a dispersed ascites form as well as a solitary mass form involving the omentum. The total number of tumor cells in the ascitic fluid and the dry weight of the mass were determined. The three TPN groups did not differ in tumor cell count, solid tumor weight, ratio of tumor cell count to final host weight, or ratio of solid tumor to final host weight. The mean ratio of ascites tumor cell count to host weight was not different between the rat food-fed group and any of the TPN groups. The mean ratio of solid tumor to host weight was less for the TPN groups than for rat food-fed animals. We conclude that TPN had no adverse effect on the growth of tumor vs. host and that the source of intravenous calories (fat or carbohydrate) did not influence the relative growth of tumor and host in this TPN-tumor model.

Effect of intravenous fat emulsion on experimental acute pancreatitis

The known relationship of hyperlipidemia and pancreatitis raises the question whether intravenous fat emulsion is detrimental in acute pancreatitis. Pancreatitis was induced in 52 male Sprague-Dawley rats followed by placement of a jugular catheter which was anchored to the back with a Teflon button. The animals were placed NPO in metabolic cages and continuously infused, initially with normal saline. The 37 animals surviving 24 hr were randomly assigned to group I (mean iv intake: glucose 222 kcal/kg/day; amino acids 13.1 g/kg/day) or group II (glucose 191 kcal/kg/day; intravenous fat emulsion 10% 47 kcal/kg/day; amino acids 12.9 g/kg/day). Nine animals were eliminated from the study because of mechanical problems leaving 14 in each group for analysis. Per cent survival on days 3, 5, and 7 was 64, 50 and 36 in group I, and 50, 36 and 36 in group II. Mean urinary amylase excretion was 244 +/- 185 units/day in group I and 262 +/- 127 units/day in group II. There was no significant difference in survival or urine amylase excretion nor in pancreatic histology or gross appearance of the animals between the two groups. In this model of acute pancreatitis, intravenous fat emulsion was not detrimental as measured by survival, urinary amylase excretion, and pancreatic histology.

Reversal of skin test anergy during maintenance hemodialysis by protein and calorie supplementation

The effect of protein and calorie supplementation on the immune function of two maintenance hemodialysis patients was assessed. Before nutritional supplementation, both patients were anergic to four skin test antigens and had low relative percentages and absolute number of T lymphocytes. After 3 months of nutritional supplements both patients responded to in vivo skin testing to at least two antigens and in both patients, the relative percentage and absolute number of T lymphocytes increased. These two cases illustrate that the defect in cell-mediated immunity and impaired delayed cutaneous hypersensitivity which is known to occur in hemodialysis patients may be a reversible manifestation of protein-calorie malnutrition.

Enhancement of peritoneal dialysis clearance with docusate sodium

A study was done in rabbits to determine the effect of docusate sodium (DSS) on the peritoneal clearance of creatinine and urea. Following a series of control exchanges with a commercially available peritoneal dialysis solution, three animals in each of four groups received DSS (0.005%, 0.01%, 0.02%, or 0.04%) in a single exchange, followed by 10 subsequent exchanges of control fluid. Creatinine and urea clearances were measured for each exchange. Comparison of post-DSS clearances (exchanges 5 through 15) with pre-DSS baseline values (exchanges 1 through 4) showed a mean percent increase in creatinine clearance that was proportional to the concentration and ranged from 74% to 244% above baseline. Similarly, urea clearance increased by 79 to 166%. The effect on both creatinine and urea clearance persisted through the completion of the dialysis procedure. No animals showed signs of toxicity from DSS. The mechanism of the DSS effect on clearance is unknown. Although studies are needed to delineate the mechanism of the effect and to identify potential toxic effects, the results of this study indicate that DSS has a significant effect on clearance of both creatinine and urea.