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Biomedical subjects

J T DiPiro

Publications and source records attributed to J T DiPiro.

At least 19 recordsLinked to original sources
PubMed1992

Novel drug-delivery systems for hypertension.

Although novel controlled-release drug-delivery systems have been used in other areas of medicine, their application in the treatment of hypertension has been relatively recent. Biotechnical use of chemical-dispensing systems has been applied to propranolol, clonidine (the transdermal therapeutic system), nifedipine (the gastrointestinal therapeutic system), verapamil (the sodium alginate and spheroidal oral-delivery absorption system), felodipine (the hydrophilic gel principle), metoprolol succinate (the multiple-unit pellet system), and diltiazem (one system comprising sustained-release beads and the other utilizing the patented Geomatrix extended-release system). Oral drug-delivery systems allow antihypertensive agents that previously had to be administered two to four times daily to be administered once each day. Potential disadvantages of the oral controlled-release products include delayed attainment of pharmacodynamic effect, unpredictable or reduced bioavailability, enhanced first-pass hepatic metabolism, dose dumping, sustained toxicity, dosing inflexibility, and increased cost. Potential advantages include reduced dosing frequency, enhanced compliance and convenience, reduced toxicity, stable drug levels, uniform drug effect, and decreased total dose. Although skin reactions are common, the transdermal drug delivery of clonidine provides another innovative approach to supplying transcutaneous, controlled, continuous delivery of drug for 7 days. It is possible that future research will prove that the agents that provide complete 24-hour control may reduce the cardiovascular events associated with the early-morning blood pressure surge. This evolution in antihypertensive therapy to achieve once-daily dosing may prove to be of great value to both physicians and patients in the 1990s.

Administration, Cutaneous↗
PubMed1992

Novel antibody drug products.

Recent developments in protein and genetic engineering methods have allowed the production of antibody-derived molecules that have important potential as therapeutic agents. Although monoclonal antibodies of murine origin have been used for therapeutic purposes, limitations due to anti-antibody responses and suboptimal effectiveness for some indications, such as tumor cell killing, have led to the development of human monoclonal antibodies, chimeric and complementarity determining-region grafted antibodies, immunotoxins, and other engineered products. These novel antibodies are being tested for the treatment and prevention of infectious diseases and for the diagnosis and treatment of cancers, as well as for indications considered nontraditional for antibodies (e.g., as antithrombotics or inhibitors of neutrophil adherence). The availability of antibody drug products raises a number of issues for clinicians. Among these are new patterns of adverse effects, immunogenicity (development of anti-antibody response), important questions regarding administration and dosage, and substantial cost implications.

Antibodies↗
PubMed1992

Total IgE in plasma is elevated after traumatic injury and is associated with sepsis syndrome.

Gamma E immunoglobulin (IgE) is associated with allergic reactions, but has not been described as being activated after trauma or sepsis. Total plasma IgE concentrations were determined in 32 patients with major traumatic injury, 29 patients undergoing elective abdominal operations, and 30 healthy volunteers. Mean total IgE concentrations were 271.7 ng/mL, 52.3 ng/mL, and 41.3 ng/mL, respectively (p less than 0.01 for each comparison with the trauma group). Total IgE concentrations in trauma patients at the time of admission were not significantly different from elective surgical controls, and tended to increase during the intensive care unit stay. In the trauma group, total IgE concentration was significantly greater in the 18 patients that developed sepsis syndrome compared with those that did not (p = 0.034). These data suggest that allergic mechanisms may be involved in the physiologic response to major traumatic injury and sepsis syndrome, or that other cells known to be involved in the immune responses to trauma and sepsis (macrophages, platelets, and B lymphocytes) may become activated by IgE-dependent mechanisms.

Acute Kidney Injury↗
PubMed1992

Effect of experimental hemorrhagic shock on hepatic drug elimination.

OBJECTIVE: Exogenous substrates were used to measure hepatic function for the purposes of determining organ dysfunction and to evaluate the effect of experimental hemorrhagic shock with resuscitation on hepatic drug elimination. DESIGN: Prospective, controlled, non-randomized crossover trial. INTERVENTIONS: Eleven chronically instrumented immature swine were studied using a fixed-volume hemorrhage model (45 mL/kg blood removal over 15 mins) followed by resuscitation with lactated Ringer's solution at three times the volume of shed blood. One week before and immediately after hemorrhage and resuscitation, hepatic function markers (indocyanine green and antipyrine) were simultaneously administered intravenously. MEASUREMENTS: Physiologic data and blood samples were collected over 12 hrs after drug administration. Drug clearances, volumes of distribution, and half-lives were determined. MAIN RESULTS: For indocyanine green, there was no substantial change in pharmacokinetics from preshock to postshock, suggesting minimal change in hepatic blood flow. For antipyrine, clearance was decreased by 30% after shock and resuscitation (p = .05), suggesting that oxidative metabolism was acutely impaired. CONCLUSIONS: The information indicates that hepatic oxidative drug metabolism may be impaired early after hemorrhagic shock and that dosages of drugs in this class should be carefully examined when administered to patients who have sustained injury with hemorrhagic shock.

Animals↗
PubMed1991

Aminoglycoside combinations versus beta-lactams alone for penetrating abdominal trauma: a meta-analysis.

Despite several small comparative clinical trials, controversy persists over the best choice of antimicrobial therapy for penetrating abdominal trauma. Some still question whether single drug regimens are as effective as the traditional combinations containing an aminoglycoside. A meta-analysis was performed to address this issue. Meta-analysis is a relatively new statistical tool whereby data from a number of clinical trials is analyzed and pooled to produce useful and more reliable data. In this study, a meta-analysis of 17 published randomized trials was performed to assess the effectiveness of single beta-lactam antimicrobials versus combinations containing aminoglycoside when used for penetrating abdominal trauma. The overall summary odds ratio of the pooled results of these trials was 0.96 (p = 0.833) with a 95% confidence interval of 0.30-3.05. Since not significantly different from unity (1.0), we conclude that single beta-lactam antimicrobials are as effective as traditional combinations containing aminoglycoside in this setting.

Abdominal Injuries↗
PubMed1990

Blood kinetics, tissue distribution, and radioimaging of anti-common chronic lymphatic leukemia antigen (cCLLa) monoclonal antibody CLL2 in mice transplanted with cCLLa-bearing human leukemia cells.

The blood kinetics and biodistribution of anti-common chronic lymphatic leukemia antigen (cCLLa) monoclonal antibody (MoAb) CLL2 were assessed in mice bearing cCLLa+ tumors. The cCLLa is a 69-Kd glycoprotein antigen expressed selectively by malignant B cells in human CLL, hairy cell leukemia (HCL), and prolymphocytic leukemia. Immunoreactive 125I-CLL2 (5 micrograms/mouse, specific activity 4.3 microCi/micrograms) was injected intravenously in mice bearing HCL-derived EH xenografts, and blood kinetics and biodistribution were ascertained up to 16 days postinjection. Radioimages were also obtained up to 72 hours after injecting 10 micrograms/mouse (specific activity 50.1 microCi/micrograms) of 125I-CLL2. Distinct 125I-CLL2 blood kinetics were observed in EH engrafted compared with tumor-free mice including: a longer 125I-CLL2 T 1/2 (153 hours v 72 hours), and a considerably greater blood clearance (173 mg/h v 54.7 mg/h) with biexponential rather than monoexponential configuration; and a greater volume of antibody distribution (31,483 mg v 5,729 mg). These data suggest more rapid tissue uptake by grafted tumours. Preferential 125I-CLL2 uptake by EH tumours relative to normal tissues was observed beginning 24 hours postinjection (mean ratio, 4.2) with average peak tumor 125I-CLL2 levels of 428.7 pg/mg. 125I-CLL2 uptake selectivity by EH tumor cells was also supported by: (1) negligible 125I-CLL2 uptake by cCLLa- Molt-4 xenografts (average 29.1 pg/mg 24 hours postinjection); (2) background uptake of cCLLa-irrelevant MoAb 131I-LEU1 by CD5- EH xenografts (average 31.4 pg/mg 48 hours postinjection); and (3) by scintigraphy. The EH xenograft mouse model might be useful to ascertain preclinically the anti-tumor effect of anti-cCLLa MoAbs and of their conjugated derivatives.

Animals↗
PubMed1990

Assessment of cefazolin and cefuroxime tissue penetration by using a continuous intravenous infusion.

A continuous intravenous infusion was used to assess the tissue penetration of cefazolin (14 subjects) and cefuroxime (15 subjects) in orthopedic surgery patients. Subjects were randomly assigned to receive a continuous intravenous infusion of cefazolin (mean, 178.6 mg/h) or cefuroxime (mean, 330.0 mg/h) at a rate estimated to achieve a target steady-state total concentration of 50 micrograms/ml in serum. The infusion was initiated 12 to 14 h before surgery, and blood and muscle tissue samples were collected intraoperatively at the times of incision and wound closure. Although there was a significant difference between the free concentrations of cefazolin (at incision, 9.3 micrograms/ml; at closure, 9.2 micrograms/ml) and cefuroxime in serum (at incision, 26.9 micrograms/ml; at closure, 31.8 micrograms/ml), there was no difference in the total concentrations in muscle at either surgical incision (cefazolin, 6.1 micrograms/g; cefuroxime, 5.6 micrograms/g) or wound closure (cefazolin, 7.7 micrograms/g; cefuroxime, 7.4 micrograms/g). There was a significant correlation between the pooled free serum and total muscle concentrations for cefazolin (P = 0.001); however, there was no correlation between these variables with the pooled cefuroxime data (P = 0.403). These findings indicate that the free drug concentration in serum alone is not consistently predictive of the total concentration of cephalosporin in muscle.

Cefazolin↗
PubMed1990

Pathophysiology and treatment of gram-negative sepsis.

The pathogenesis, clinical presentation, and complications of gram-negative bacterial sepsis are described, and the implications for therapy are reviewed. The sepsis syndrome is a clinically defined condition that involves the physiologic alterations and clinical consequences of the presence of microorganisms or their toxins in the bloodstream or tissues. Gram-negative bacteria produce sepsis and septic shock via the release of the cell-wall component known as endotoxin (lipopolysaccharide). The lipid A moiety, common to gram-negative bacteria, is immunogenic and appears to account for many of the biologic effects of endotoxin. A variety of mediators, including tumor-necrosis factor, are released in response to endotoxin, with resultant diverse effects on host tissues, including organ dysfunction and shock. Adequate treatment requires prompt recognition of infection, especially endotoxemia and sepsis, and the early institution of appropriate therapy. Corticosteroids offer little benefit, and the efficacy of naloxone and nonsteroidal anti-inflammatory drugs has not been determined. Although suitable antimicrobial therapy is necessary to eliminate the offending organisms, antimicrobial agents do not inhibit the effects of the bacterial toxins that are present in sepsis. The outcome of sepsis may be favorably influenced in the future by the use of newer methods of detection and newer treatment modalities, including monoclonal antibodies directed against endotoxin or inhibitors of inflammatory mediators.

Bacterial Infections↗
PubMed1989

Controlling drug effects through improved oral formulations. The pharmacokinetics of the prazosin gastrointestinal therapeutic system.

Influences that determine a drug's effects include pharmacokinetic factors (the serum concentrations of drug as determined by the drug dose, absorption, distribution, and excretion) and pharmacodynamic factors (the intensity of drug effect). Most assessments of drug effect focus on the therapeutic range, i.e., the serum concentrations below which therapeutic effects are unlikely and above which toxic effects may be seen. A goal for many treatment regimens is to maintain serum drug concentrations within the therapeutic range. Maintenance of drug concentrations within the therapeutic range can be difficult with many traditional oral dosage formulations. Soon after administration of standard tablets, capsules, or liquids, a pronounced peak level is observed in serum. At the end of a dosage interval, serum concentrations are frequently below those needed to exert therapeutic effect. One reason for the wide range in serum concentrations with standard oral formulations is that these products usually exhibit first-order drug absorption, in which the rate of absorption from the gastrointestinal tract continually varies following a dose (from high to low) and is directly determined by the amount of drug remaining in the gastrointestinal tract. First-order absorption, therefore, results in changing absorption rates, wide swings in serum drug concentrations, a relatively short duration of action, and often, inconsistent drug effects over a dosage interval. One way to address the problems with standard oral products that have first-order absorption is to produce products that control drug release and absorption. A large number of controlled-release oral products are now on the market and use a variety of technologies. The ideal controlled-release formulation would result in zero-order drug absorption, in which the rate of drug absorption from the gastrointestinal tract would be constant and not determined by the amount of drug in the gastrointestinal tract. Zero-order absorption, therefore, results in an unchanging absorption rate, consistent serum levels, a longer duration of action, and more steady drug effect. Zero-order absorption is particularly preferable in situations that require a consistent, long-term therapeutic effect, e.g., in patients with hypertension, asthma, or arrhythmias. Of all the controlled-release preparations on the market, however, very few exhibit zero-order absorption; most can be categorized somewhere between first- and zero-order kinetics. An advanced-technology tablet has been invented to produce zero-order drug absorption for prazosin and nifedipine.(ABSTRACT TRUNCATED AT 400 WORDS)

Administration, Oral↗
PubMed1989

Relationship of plasma clonidine to growth hormone concentrations in children and adolescents.

The relationships of plasma clonidine to increases in growth hormone, blood pressure response and degree of sedation were studied in nine children with short stature after a 0.15 mg/m2 oral clonidine tolerance test. A direct correlation was found between the peak plasma clonidine concentration and the increase in plasma growth hormone (P = 0.055). The patients experienced varying degrees of blood pressure reduction and sedation that were unrelated to age. No correlation was found between the plasma clonidine concentration and degree of blood pressure reduction or degree of sedation. The half-life of oral clonidine ranged from 1.75 to 2.38 hours, which is significantly less than that for adults.

Adolescent↗
PubMed1989

A comparison of monobactam antibiotics in surgical infections.

The introduction of gentamicin almost 20 years ago provided an effective option for the treatment of gram-negative bacillary infections. During the past few years, the availability of aztreonam (a monobactam), imipenem (a carbapenem), and newer cephalosporins within vitro activities comparable with aminoglycosides against many gram-negative bacilli, has stimulated a reassessment of the role of aminoglycosides in treating these infections. When determining the role of new antimicrobials as potential replacements for more established agents, the clinical focus should be on three factors: comparative efficacy, safety, and cost. Consideration of cost is relevant only when efficacy and safety are equivalent. Other factors, such as comparative in vitro antimicrobial activity, pharmacokinetics, and effect on normal flora can also influence the selection of an antimicrobial regimen. A new class of antimicrobials, the monobactams, is the focus of this review. The only member of this class currently in clinical use is aztreonam. A comparison with aminoglycosides is particularly relevant because aztreonam is active against aerobic gram-negative bacilli. This review will discuss the acknowledged concerns with aminoglycoside use and compare the characteristics of aztreonam and currently marketed aminoglycosides.

Aminoglycosides↗
PubMed1989

Single-dose cefmetazole versus multiple dose cefoxitin for prophylaxis in abdominal surgery.

One hundred and ninety-five patients undergoing abdominal surgical procedures completed a multicentre, randomized, open-label study comparing the safety and efficacy of cefmetazole and cefoxitin for the prevention of postoperative wound infection. Cefmetazole was administered iv in a single 2 g dose given within 90 min of the operation. Cefoxitin was administered in a single 2 g, similarly timed, preoperative dose and two additional doses given at 6 h intervals after surgery. For operations that exceeded 2-4 h duration an additional dose of each agent was administered. Patients undergoing colorectal operations received oral neomycin and erythromycin as bowel preparation. Colorectal operations were performed most frequently (49% of patients) followed by cholecystectomies (26%) and gastroduodenal procedures (21%). The operative site infection rate was 6.5% for cefmetazole and 7.7% for cefoxitin (P greater than 0.05). Serious drug related adverse effects were not observed. This study demonstrates that administration of single-dose cefmetazole is as effective as a standard three dose regimen of cefoxitin for prophylaxis with abdominal operations.

Abdomen↗
PubMed1989

Comparative intraoperative concentrations of two cephalosporins with activity against anaerobic bacteria.

We determined the intraoperative concentrations of cefmetazole and cefoxitin in serum and muscle from the wound of 30 patients who were undergoing cholecystectomies. The study employed an open-label design in which all patients randomly received cefoxitin sodium (30 mg/kg) or cefmetazole sodium (15 or 30 mg/kg) intravenously with the induction of anesthesia. Total serum and wound-muscle concentrations achieved with cefmetazole 30 mg/kg were significantly greater than those achieved with a similar dose of cefoxitin. Cefmetazole in a 15 mg/kg dose was comparable with cefoxitin 30 mg/kg in achieved concentrations. The elimination half-life for cefoxitin was much shorter than that for cefmetazole (41 min v. 64-68 min, respectively) and this relates to a shorter duration of action for the former. The choice of agent for surgical prophylaxis should incorporate factors relating to drug pharmacokinetic properties as well as microbiological factors.

Adolescent↗
PubMed1989

Pharmacokinetics of gentamicin in neonates on extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation (ECMO) has been used in more than 1,000 infants in 50 centers in the United States. The extracorporeal circuit contains approximately 400 ml of blood, an amount exceeding the blood volume of most full-term neonates. The effect of this additional blood volume on drug disposition is unknown. In this study, we determined the pharmacokinetic parameters of gentamicin in 10 infants on ECMO. Gentamicin concentrations were determined by a fluorescence polarization immunoassay. Pharmacokinetic parameters were determined from these concentrations by using a two-compartment model. Our study demonstrated a mean steady-state volume of distribution of 0.51 +/- 0.11 liters/kg, a figure similar to that in previous studies of full-term infants. The elimination half-life was found to be prolonged (mean, 573 +/- 263 min). The creatinine level in the plasma of the infants was found to be a statistically significant predictor of elimination half-life. Recommendations regarding initial dosing levels of gentamicin in infants on ECMO are made.

Blood Urea Nitrogen↗
PubMed1988

Use of serum drug concentrations in surgical patients.

Surgical patients frequently require drug treatments that can be assessed with serum drug concentrations. Of the agents for which serum drug concentrations are routinely available, the aminoglycosides theophylline, vancomycin, digoxin, and phenytoin are used most frequently in surgical patients. When using serum drug concentrations, the clinician should have an understanding of the relationships (or lack of) between drug concentrations and therapeutic or toxic effects. When blood is collected for serum concentration determinations, the exact timing of the sample in relation to the dose must be considered. For some drugs, (such as the aminoglycosides, it is necessary to determine peak and trough concentrations, whereas for other agents, like theophylline, the average or mid-dose level may be more important to consider. There are many factors that affect serum drug concentrations. Among these are various disease states, obesity, fluid imbalances, the drug dosage form used, and concurrent drug use. Not all patients require serum drug concentration monitoring; however, with each drug there are high-risk patients who may benefit. When used properly, serum drug concentrations may be helpful in maximizing therapeutic benefits, minimizing or diagnosing drug toxicity, and assessing patient compliance with drug regimens.

Aminoglycosides↗