Emerging bacterial pathogens: a consensus of the scientific data and the risk for development of multiple organ dysfunction syndrome

Antibiotic resistance in the hospital setting is continuing to increase, particularly in intensive care units (ICUs) and other areas of the hospital such as oncology units, where the use of empiric broad-spectrum antibiotics is common. The problem of antibiotic resistance is also compounded in the immunocompromised patient. Multi-drug resistance is common among both Gram-positive and -negative bacteria, and becoming more prevalent among fungi (yeast). Two major antibiotic-resistant pathogens include extended-spectrum beta-lactamase producing Klebsiella pneumoniae (ESBL-KP) and vancomycin-resistant enterococci (VRE). When infections occur with ESBL-KP, a carbapenem antibiotic is usually the drug of choice. When infection occurs with VRE, specific therapy is bacteriostatic, and the clinician may have to rely on empirically selected antibiotics or combinations of antibiotics to achieve a positive outcome. Two newly-approved agents, linezolid and quinupristin/dalfopristin can be used to treat infections caused by resistant gram-positive cocci, but the latter is approved for use against VR-E. faecium. Risk factors for the development of ESBL-KP include the use of extended-spectrum cephalosporins such as ceftazidime. Risk factors for the development of VRE include inappropriate use of vancomycin, extended-spectrum cephalosporins, and antianaerobic drug therapy such as clindamycin. Several institutions have documented a reduction in one or both of these resistant pathogens following a decrease in the use of extended-spectrum cephalosporins combined with the increased use of extended-spectrum penicillins/beta-lactamase inhibitor combinations, such as piperacillin/tazobactam, for the empiric therapy of infections. For VRE, a reduction in the inappropriate use of vancomycin is also an important interventional strategy along with improved infection control practice.

Overview of resistant gram-positive pathogens in the surgical patient

Staphylococci and enterococci are the most common pathogens in surgical-site and bloodstream infections. The emergence of drug resistance among these gram-positive bacteria thus poses a substantial threat to patients with surgical infections. Resistance to methicillin/oxacillin is frequently observed in Staphylococcus aureus isolates and is often accompanied by multidrug resistance. Vancomycin is usually the treatment of choice for infections caused by methicillin-resistant S. aureus (MRSA), so the recent appearance of S. aureus isolated with intermediate sensitivity to vancomycin is cause for concern. Vancomycin resistance has already appeared in most species of enterococci. Infections caused by vancomycin-resistant enterococci (VRE) are associated with increased mortality compared to infections caused by vancomycin-sensitive isolates. Measures for preventing vancomycin resistance include reducing the use of vancomycin and other agents that appear to be associated with VRE, including third-generation cephalosporins and anti-anaerobic drugs. Third-generation cephalosporins have also been implicated in the increased prevalence of MRSA infections. Prudent use of existing antibiotics is an essential strategy for combating the rising tide of drug-resistant gram-positive pathogens.

Levofloxacin failure in a patient with pneumococcal pneumonia

OBJECTIVE

To report a case of levofloxacin failure in a patient with a penicillin-sensitive Streptococcus pneumoniae pneumonia.

CASE SUMMARY

A previously healthy, immunocompetent, 53-year-old white man presented with penicillin-sensitive S. pneumoniae pneumonia. The patient was empirically placed on levofloxacin monotherapy, which was continued due to a local penicillin shortage. When the patient failed to improve, further susceptibility testing was ordered. The organism was found to have a penicillin minimum inhibitory concentration (MIC) of 0.023 microgram/mL and a levofloxacin MIC of 6 micrograms/mL. Effective antimicrobial therapy was delayed, as clinicians did not anticipate fluoroquinolone resistance.

DISCUSSION

Newer fluoroquinolones such as levofloxacin have good activity against most S. pneumoniae isolates and are used for the treatment of pneumonia. Although resistance to these agents is rare, it has been reported. Current guidelines from the National Committee for Clinical Laboratory Standards do not recommend initial fluoroquinolone susceptibility testing.

CONCLUSIONS

As fluoroquinolone resistance may not be identified by susceptibility patterns to other antibiotics, early fluoroquinolone susceptibility testing and increased awareness of resistance may aid clinicians in their treatment of pneumococcal disease.

Development of a best-practice model at a university hospital to increase efficiency in the management of patients with community-acquired pneumonia

An economic evaluation of drug acquisition, nursing care, pharmacy time, laboratory costs, supplies, and ancillary care was conducted as a first step toward developing a pneumonia management plan at the University of Kentucky Medical Center (UKMC). UKMC costs were compared with costs at other hospitals treating pneumonia patients on Medicare. Overall costs for pneumonia at the 25% of hospitals nationwide with the lowest costs for Medicare patients with this condition were determined and compared with costs at UKMC. Against nationwide benchmarks, efficiencies at UKMC for treating simple pneumonia ranged from 45% for pharmacy expenses to 81% for nursing costs. Efficiencies for complicated pneumonia ranged from 47% for laboratory costs to 67% for nursing costs. The most cost-efficient antimicrobial treatment options were promoted and integrated into a pneumonia management plan based on Infectious Diseases Society of America treatment guidelines. A comparison of pneumonia treatment costs at UKMC with those at the 25% of hospitals nationwide with the lowest treatment costs for Medicare patients with pneumonia revealed that UKMC pharmacy costs could be optimized. Strategies for standardizing the care of patients with community-acquired pneumonia (CAP) are being implemented.

Polymyxin B sulfate and colistin: old antibiotics for emerging multiresistant gram-negative bacteria

BACKGROUND

Polymyxin B sulfate and colistin, also known as colistimethate, have not been used for many years because less toxic antimicrobials are available. Gram-negative bacteria that are resistant to the aminoglycosides, beta-lactams, and fluoroquinolones are becoming more common. These bacteria are often susceptible to the polymyxins.

OBJECTIVE

To present a review of the chemistry, antibacterial spectrum, dosing, pharmacokinetics, toxicity, and indications for polymyxin B sulfate and colistin.

DATA SOURCE

A MEDLINE search (1966-1998) of the English-language literature was performed to identify primary literature on the polymyxins. Older citations ( 1949-1965) were identified through the bibliographies of these articles.

STUDY SELECTION

All available reports of in vitro antibacterial activity, animal and clinical trials, and case reports were reviewed.

DATA SYNTHESIS

The polymyxins are amphipathic molecules that interact with lipopolysaccharide in the bacterial outer membrane. They have potent antiendotoxic properties and antibacterial activity against Pseudomonas aeruginosa and many of the Enterobacteriaceae. Polymyxin B and colistin are usually given at a dose of 1.5-2.5 and 5 mg/kg/d, respectively, in two divided doses. Dosing must be altered in renal failure since the kidney is the primary route of elimination. Distribution into pleural fluid, joints, and cerebrospinal fluid is poor. Toxic effects involve the kidney and central nervous system. The polymyxins are recommended for serious systemic infections caused by gram-negative bacteria that are resistant to other agents.

CONCLUSIONS

Polymyxin B sulfate and colistin have a role in the therapy of multidrug-resistant gram-negative bacterial infections.

Azithromycin versus erythromycin for community-acquired pneumonia: a cost-minimization analysis

The costs of i.v. erythromycin versus azithromycin (in terms of medication use and treatment of adverse effects) when these drugs were used with other antimicrobials to treat community-acquired pneumonia (CAP) were compared. The medical records of patients receiving i.v. azithromycin or erythromycin as part of combination antimicrobial therapy for the treatment of CAP at a 473-bed level 1 trauma center in Kentucky were retrospectively reviewed. Data were collected for patients treated from December 1, 1997, through March 31, 1998. Patient data collected included occurrence of phlebitis or pain at the injection site, number of line changes due to phlebitis, and culture results. Cost data collected included drug acquisition cost, pharmacy cost of drug preparation, nursing time to administer the agent, cost of drug supplies, and cost of managing complications. Three time-and-motion studies were conducted to determine technician preparation time and pharmacist verification time. The medical records of 62 patients were identified and reviewed; 50 patients were enrolled in the study (25 in the azithromycin group and 25 in the erythromycin group). The average total days of therapy was 5.1 for the azithromycin group and 5.6 for the erythromycin group. The average total cost, including the cost of complications ($4.36 per patient in the erythromycin group), was $66.46 in the azithromycin group and $96.56 in the erythromycin group. The difference in costs between the two groups was not significant. There was no significant cost difference between azithromycin- and erythromycin-containing combination antimicrobial therapy in the treatment of CAP.

Antimicrobial resistance in gram-positive bacteria: the myth of the MIC. Minimum inhibitory concentration

Although much progress has occurred in the fight to treat infection, resistant bacteria increasingly are becoming problematic. The minimum inhibitory concentration is easily determined, yet its definition, clinical application, and relevance are confusing. In addition, errors can occur during in vitro susceptibility testing. The mechanism of resistance for different organisms is discussed as are the pitfalls of susceptibility testing and the prescription of antimicrobial agents.

Vancomycin use in a university medical center: effect of a vancomycin continuation form

OBJECTIVE

To examine the impact of a new policy to ensure appropriate use of vancomycin in a 461-bed tertiary-care hospital.

DESIGN

We instituted a policy that allowed physicians to prescribe vancomycin but that required them to complete a vancomycin continuation form and document that use conformed to Hospital Infection Control Practices Advisory Committee (HICPAC) guidelines if they wished to continue the drug beyond 72 hours. Vancomycin was stopped automatically at 72 hours if use was not consistent with guidelines, if an infectious diseases consultant did not approve the drug, or if the form was not completed. A pharmacist and infectious diseases specialist monitored use of vancomycin prospectively and interacted with prescribers when indicated. Educational efforts were limited to printing the HICPAC guidelines on the form and providing information about the policy in a newsletter. Patterns of prescribing and the economic impact of the form were evaluated over a 6-month period.

RESULTS

Only 29% to 48% of vancomycin orders initially met HICPAC guidelines, but 77% to 96% of use was appropriate after 72 hours when the form was used. Inappropriate surgical prophylaxis, empirical therapy of intensive-care unit and transplant patients, and therapy for inadequately documented coagulase-negative staphylococcal infections remained problems. Vancomycin use fell from a mean of 136 (+/-52) g/1,000 patient days in the 12 months before the form to 78 (+/-22) g/1,000 patient days in the 9 months after institution of the form (P<.05). Net vancomycin acquisition costs and costs of ordering vancomycin serum levels fell by $357 and $19 per 1,000 patient days, respectively (P<.05). This represented annualized saving of approximately $47,000 in drug and monitoring costs. No adverse patient outcomes were seen as a result of the program.

CONCLUSIONS

A vancomycin continuation form can decrease inappropriate vancomycin use and may save money. Additional educational efforts may be required to increase compliance with HICPAC guidelines during initial prescribing.

Pharmacokinetics and pharmacodynamics of intravenous and oral azithromycin: enhanced tissue activity and minimal drug interactions

OBJECTIVE

To review the pharmacokinetics and pharmacodynamics of oral and intravenous azithromycin compared with other macrolide antibiotics, and to evaluate these differences and their relation to clinical effectiveness.

DATA SOURCE

A MEDLINE search (1966-May 1998) was performed to identify applicable English-language clinical, animal, and microbiologic studies pertaining to pharmacokinetic and pharmacodynamic parameters.

STUDY SELECTION

Relevant studies concerning microbiology, pharmacokinetics, tissue concentrations, pharmacodynamics, and the clinical effects of these parameters were selected.

DATA SYNTHESIS

The structural modification that distinguishes the azalide antibiotics from the macrolide antibiotics is responsible for the pharmacokinetic and pharmacodynamic behavior of azithromycin, resulting in the high and sustained tissue and intracellular concentrations seen with this agent. Drug delivery to the site of infection by phagocytes and fibroblasts is the hallmark of azithromycin's tissue-directed pharmacodynamics, allowing for convenient once-daily, 5-day regimens for most infections that respond to oral therapy and 7-10 days for more serious infections requiring initial intravenous therapy. Metabolism is via hepatic pathways other than cytochrome P450, thus minimizing the risk of drug interactions.

CONCLUSIONS

Compared with other macrolide antibiotics, the unique pharmacokinetic and pharmacodynamic features of azithromycin offer the potential for improved efficacy and safety from drug interactions. These attributes, combined with its once-daily dosing schedule, make azithromycin suitable for the treatment of many types of bacterial infection.

Amphotericin B lipid complex

OBJECTIVE

To evaluate the published data on the effectiveness and safety of amphotericin B lipid complex (ABLC) for the treatment of invasive mycosis and to evaluate data describing the pharmacologic properties and pharmacokinetic behavior of ABLC in both animals and humans.

DATA SOURCE

A MEDLINE search was conducted to identify literature published from 1965 to January 1997 for amphotericin B deoxycholate (DCAB) and ABLC. In addition, preliminary data published as abstracts and presented at national conferences on infectious disease and hematology within the last 6 years were also included in this review.

STUDY SELECTION

Both human and animal studies were reviewed. Animal and in vitro studies were selected to evaluate the pharmacologic and toxicologic properties of ABLC. For the evaluation of the efficacy, safety, and pharmacokinetic behavior of ABLC, large, well-controlled studies were reviewed. In addition, data from open-label and emergency use protocols were also included in the review.

DATA EXTRACTION

The study and analytical methods, results, and conclusions of the selected studies were evaluated. Pharmacokinetic data for both ABLC and DCAB that were derived from human subjects were also evaluated.

DATA SYNTHESIS

DCAB has been the cornerstone for the treatment of invasive mycosis, even though it has a narrow therapeutic index. Infusion-related toxicities (e.g., fever, chills, rigors) are likely due to DCAB stimulation of cytokine and prostaglandin synthesis. Conversely, nephrotoxicity, the primary non-infusion-related toxicity, likely results from the nonselective cytotoxic interaction between DCAB and cholesterol-containing mammalian cells. ABLC represents a new approach to improving the therapeutic index of DCAB. Mammalian cytotoxicity is attenuated by complexing amphotericin B to a mixture of phospholipids. This alters the affinity of amphotericin B and decreases its selective transfer from the complex to cholesterol-containing mammalian cells. Fungi also possess lipase, which improves the selective transfer from the complex to ergosterol-containing cell membranes. In humans, the lipid formulation increases the volume of distribution of amphotericin B. Thus, compared with DCAB, larger doses of ABLC can be administered for a longer duration with less nephrotoxicity. However, the prevalence of infusion-related toxicities associated with ABLC is similar to that of DCAB. Whether the alteration in distribution improves efficacy by improving tissue concentrations of amphotericin B has not been determined. The cost of this agent will limit its use.

CONCLUSIONS

ABLC has been shown to be at least as effective as DCAB, and it has been well tolerated in the clinical studies to date. Despite large dosages and extended courses of administration, there is little nephrotoxicity associated with its use. However, the cost of this agent will limit its use to the treatment of refractory mycosis or to cases where DCAB is contraindicated due to significant renal insufficiency.

Intra-arterial urokinase versus surgery for acute peripheral arterial occlusion

The outcomes of intra-arterial urokinase versus surgery for acute peripheral arterial occlusion (PAO) were compared. Patients at a university hospital who had received intraarterial urokinase for PAO were identified by computer and pair-matched on the basis of comorbidities, age, sex, and site of occlusion to computer-selected patients who had undergone surgery. Only patients with category I or II ischemia were considered. The study period for the urokinase group was February 1995 through January 1996, and the period for the surgery group was June 1993 through January 1996. Twenty-eight patients in each group met the selection criteria. Patients who had received urokinase had a significantly shorter median length of stay (8.5 days) than patients in the surgery group (13 days) and significantly fewer infectious complications (2 versus 10). No differences in amputation rates, total hospital costs, or mortality rates were detected. Patients who received intra-arterial urokinase for PAO had a shorter length of stay in the hospital and fewer infectious complications than those who underwent surgery.

Intravenous insulin-like growth factor-I (IGF-I) in moderate-to-severe head injury: a Phase II safety and efficacy trial

The purpose of this study was to determine the effect of insulin-like growth factor-I (IGF-I) on the catabolic state and clinical outcome of head-injured patients. Thirty-three patients between the ages of 18 and 59 years with isolated traumatic head injury and Glasgow Coma Scale (GCS) scores of 4 to 10 were randomized to one of two groups. All patients received standard neurosurgical intensive care plus aggressive nutritional support; the patients in the treatment group also received intravenous therapy with continuous IGF-I (0.01 mg/kg/hour). During the 14-day dosing period, the control patients lost weight, whereas treated patients gained weight despite a significantly higher measured energy expenditure and lower caloric intake (p = 0.02). Daily glucose concentrations and nitrogen outputs were greater in control patients (p = 0.03) throughout the study period. During Week 1, only treated patients achieved positive nitrogen balance. Fifteen of 17 treated and 13 of 16 control patients survived the 1st week. No deaths occurred in patients whose serum IGF-I concentrations were higher than 350 ng/ml. Dichotomized Glasgow Outcome Scale scores for patients with baseline GCS scores of 5 to 7 improved from poor to good for eight of 12 treated patients but for only three of 11 control patients (p = 0.06). Eight of 11 treated patients with serum IGF-I concentrations that were at least 350 ng/ml achieved moderate-to-good outcome scores at 6 months, compared to only one of five patients with lower concentrations (p < 0.05). These findings indicate that pharmacological concentrations of IGF-I may improve clinical outcome and nitrogen utilization in patients with moderate-to-severe head injury.

Intravenous insulin-like growth factor-I (IGF-I) in moderate-to-severe head injury: a phase II safety and efficacy trial

The purpose of this study was to determine the effect of insulin-like growth factor-I (IGF-I) on the catabolic state and clinical outcome of head-injured patients. Thirty-three patients between the ages of 18 and 59 years with isolated traumatic head injury and Glasgow Coma Scale (GCS) scores of 4 to 10 were randomized to one of two groups. All patients received standard neurosurgical intensive care plus aggressive nutritional support; the patients in the treatment group also received intravenous therapy with continuous IGF-I (0.01 mg/kg/hour). During the 14-day dosing period, the control patients lost weight, whereas treated patients gained weight despite a significantly higher measured energy expenditure and lower caloric intake (p = 0.02). Daily glucose concentrations and nitrogen outputs were greater in control patients (p = 0.03) throughout the study period. During Week 1, only treated patients achieved positive nitrogen balance. Fifteen of 17 treated and 13 of 16 control patients survived the 1st week. No deaths occurred in patients whose serum IGF-I concentrations were higher than 350 ng/ml. Dichotomized Glasgow Outcome Scale scores for patients with baseline GCS scores of 5 to 7 improved from poor to good for eight of 12 treated patients but for only three of 11 control patients (p = 0.06). Eight of 11 treated patients with serum IGF-I concentrations that were at least 350 ng/ml achieved moderate-to-good outcome scores at 6 months, compared to only one of five patients with lower concentrations (p < 0.05). These findings indicate that pharmacological concentrations of IGF-I may improve clinical outcome and nitrogen utilization in patients with moderate-to-severe head injury.

Intravenous medication errors

In a clinical study, it was reported that based on the number of adult patients admitted to two hospitals, medication errors amounted to almost 4,000, an alarming figure considering that many were thought to be preventable. Today's healthcare environment dictates the type of care patients receive and from whom, and the potential for medication errors. This article discusses the factors concerning the prescribing of i.v. medications, preparing the medications, and administering them competently by nurses and pharmacists.

Implementation of a criteria-based antimicrobial formulary system

The development of a criteria-based antimicrobial formulary system for use in a 432-bed university-based tertiary-care hospital is described. A subcommittee of the hospital's pharmacy and therapeutics committee developed prescribing criteria for antimicrobials thought to have a specific place in the treatment of various infections. The criteria were based primarily on patient needs, but when two therapies were thought to have similar effectiveness and similar toxicity profiles, cost became the deciding factor in drug selection. Educational packets were designed to assist physicians in prescribing criteria-based antimicrobials. An antimicrobial order form was also developed. The program was implemented after an extensive orientation and education period; data on antimicrobial use were collected for the first year of the program. Hospitalwide compliance with the criteria was 89%, although compliance in certain departments was poorer. The database was formulated to be both service- and physician-specific for the purposes of reporting and education.

New macrolide antibiotics: usefulness in infections caused by mycobacteria other than Mycobacterium tuberculosis

OBJECTIVE

To compare the pharmacology, in vitro activity, and clinical use of the new macrolide antibiotics, azithromycin and clarithromycin, in the treatment of infections caused by mycobacteria other than Mycobacterium tuberculosis.

DATA IDENTIFICATION

An English-language literature search using MEDLINE (1987-1994), Index Medicus (1987-1994), Program and abstracts of the 31st (1991) and 32nd (1992) Interscience Conference on Antimicrobial Agents and Chemotherapy, and bibliographic reviews of related textbooks, review articles, and professional society publications.

STUDY SELECTION

105 articles were selected. In vitro and in vivo reports on the pharmacokinetics, microbiology, pharmacology, and effectiveness of clarithromycin and azithromycin were assessed to compare their effectiveness and safety. Emphasis was placed on the use of these new drugs in treating infections caused by Mycobacterium avium complex, Mycobacterium chelonae, and Mycobacterium fortuitum infections.

RESULTS

A review of the in vitro activity of the new macrolides revealed moderate to very good activity against many strains of mycobacteria other than M. tuberculosis. Early clinical trials show promising results in pulmonary infections, lymphadenitis, cutaneous infections, and disseminated infections.

CONCLUSIONS

The new macrolides, azithromycin and clarithromycin, show great promise for treating infections caused by these acid-fast bacteria. Clarithromycin is recommended as a component of combination therapy for the treatment of M. avium complex infections in patients with AIDS. The development of resistance in patients, particularly when these agents are used alone, has been reported.

Antibiotic agents in critical care

The practice of infectious disease and the use of antibiotics are becoming more and more complex in the critical care patient. Critical care nurses continue to play an important role in the safe administration and the postadministration monitoring of antibiotics. Important issues include the choice of drug for specific infections, the effect of pharmacokinetics, methods for safe administration, and the postadministration monitoring for effectiveness and for adverse effects.

Growth factors in nutritional support

Protein catabolism occurs in the severely stressed patient despite adequate protein supplementation. Supplementation of endogenous growth factors is one mechanism being evaluated to promote anabolism and improve nitrogen retention. Recombinant technology has provided a means to reproduce these endogenous growth factors. Both recombinant human growth hormone (rGH) and recombinant human insulin-like growth factor-1 (rhlGf-1) are undergoing clinical trials to establish their roles in nutritional support.

Fat emulsion particle-size distribution in total nutrient admixtures

The fat particle-size distribution in and physical stability of two commercially available lipid emulsions before and after their use in total nutrient admixtures (TNAs) are reported. Four TNAs without electrolytes and four TNAs with electrolytes were prepared; each type of TNA was prepared with Liposyn II and with Intralipid. Particle size was measured in the < 1-micron range by using photon correlation spectroscopy and in the 2-60-microns range by using light blockage. Admixtures with or without electrolytes were stored for two or nine days at 4 degrees C followed by one day at 25 degrees C. For the fraction of fat particles of < 1 micron in diameter, Intralipid and Liposyn II had a mean particle size of 374 and 313 nm, respectively. The admixtures containing electrolytes showed a decrease in mean particle size of about 7%. Admixtures with Intralipid contained 2 x 10(7) particles larger than 2 microns per milliliter (1.7% of total fat), compared with 1 x 10(6) particles per milliliter (0.05-0.15% of total fat) for admixtures with Liposyn II. The addition of electrolytes increased the particle counts for Liposyn II-containing admixtures. Upon storage, Intralipid-containing admixtures with electrolytes showed an initial increase followed by a decrease in the mean diameter of particles of < 1 micron. All the admixtures were stable in terms of pH and visual appearance. Intralipid-containing admixtures with electrolytes showed a decrease in the number of particles in the 2-60-microns size range, while Liposyn II-containing admixtures with electrolytes showed an increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Metronidazole

Metronidazole has proven to be a useful and inexpensive antibiotic for the treatment of T. vaginalis and bacterial vaginosis. Few alternatives exist for these two specific indications, and metronidazole will continue to play a primary role in therapy. Oral metronidazole continues to be a very inexpensive alternative to oral vancomycin for the treatment of C. difficile-induced pseudomembranous colitis. For the treatment of moderate to severe mixed aerobic/anaerobic pelvic infections, metronidazole should be considered secondarily in patients who have failed other multiple- or single-drug regimens or in patients who are infected. with anaerobic organisms resistant to other commonly used agents including clindamycin, cefoxitin, cefotetan, or ampicillin/sulbactam. Metronidazole is not a first line drug of choice for antibiotic prophylaxis in obstetric and gynecologic patients.

Clarithromycin: review of a new macrolide antibiotic with improved microbiologic spectrum and favorable pharmacokinetic and adverse effect profiles

OBJECTIVE

To compare the new macrolide antibiotic clarithromycin with erythromycin in terms of in vitro activity, pharmacokinetics, pharmacodynamics, clinical efficacy, and toxicity.

DATA IDENTIFICATION

An English-language literature search employing MEDLINE (1987-91), Index Medicus (1987-91), Program and Abstracts of the 30th Interscience Conference on Antimicrobial Agents and Chemotherapy (1990), Program and Abstracts of the 31st Interscience Conference on Antimicrobial Agents and Chemotherapy (1991), and bibliographic reviews of related textbooks and review articles.

STUDY SELECTION

Eighty-five articles were selected. Clinical trials with clarithromycin have been limited, and emphasis was placed on trials reported in the Program and Abstracts of the 30th Interscience Conference on Antimicrobial Agents and Chemotherapy and Program and Abstracts of the 31st Interscience Conference on Antimicrobial Agents and Chemotherapy.

DATA EXTRACTION

Articles were assessed for study quality and specific information addressing the stated purpose. In articles reporting the results of clinical trials, emphasis was placed on comparative efficacy and toxicity.

RESULTS OF DATA ANALYSIS

A review of 24 human trials suggests that clarithromycin is equally effective as erythromycin, penicillin VK, ampicillin, or amoxicillin for treatment of a variety of upper and lower respiratory tract or skin infections. Clarithromycin also appears to be better tolerated than these agents, with a lower incidence of gastrointestinal adverse effects. Limited clinical studies in patients with Mycobacterium leprae or Mycobacterium avium-intracellulare complex (MAI) suggest that clarithromycin may prove to be efficacious and well tolerated in the treatment of these infections.

CONCLUSIONS

Clarithromycin is as effective in vivo as erythromycin, with less gastrointestinal irritation. Additionally, clarithromycin appears to expand the traditional spectrum of macrolide antibiotics, with promising activity against M. leprae and MAI.

Choice of antibiotic in nonelective cesarean section

The use of antibiotics for prophylaxis against infection among women undergoing nonelective cesarean section has become the standard of care in the United States. Many different antibiotics have been used successfully. Single-dose regimens administered after the cord is clamped have proven just as effective as multiple-dose regimens. Although the most frequently used class of antibiotics is the cephalosporin family, the single best agent has not been determined. This study was a double-blind, randomized trial in which we compared a narrow-spectrum cephalosporin (cefazolin; n = 63) with an expanded-spectrum cephamycin (cefoxitin; n = 66) and with a broad-spectrum cephalosporin (cefotaxime; n = 60) used as a single-dose prophylaxis in patients undergoing a nonelective cesarean section. Of the 194 patients enrolled in the study, 189 were evaluable. There was no significant difference between the groups in mean age, gravidity, parity, duration of labor, duration of ruptured membranes, number of vaginal examinations, or socioeconomic status (socioeconomic status was defined by third-party coverage). There was no significant difference among the antibiotics in the incidence of immediate or delayed postoperative infections. These data indicate that a less expensive, narrow-spectrum cephalosporin is as effective as more expensive, broader-spectrum cephamycins and cephalosporins as prophylaxis for patients undergoing nonelective cesarean section.

Intravenous ciprofloxacin versus ceftazidime for treatment of nosocomial pneumonia and urinary tract infection

Intravenous ciprofloxacin and ceftazidime were compared for efficacy in the treatment of nosocomial pneumonia and urinary tract infection (UTI). Patients with nosocomial pneumonia were randomized to receive ciprofloxacin (as the lactate salt) 300 mg i.v. every 12 hours or ceftazidime (with sodium carbonate) 2 g i.v. every eight hours. Patients with UTI were randomized to receive ciprofloxacin 200 mg i.v. every 12 hours or ceftazidime 1 g i.v. every eight hours. Sputum and urine specimens were collected before, during, and after therapy. For patients with pneumonia, the organisms most frequently isolated before treatment began were Escherichia coli, Haemophilus influenzae, Klebsiella pneumoniae, and Proteus mirabilis. Of the 17 pneumonia patients who completed ciprofloxacin treatment, 15 (88%) had resolution of signs and symptoms or improvement. Of the 15 ceftazidime-treated pneumonia patients, 13 (87%) had resolution or improvement. Staphylococcus aureus, Streptococcus species, Acinetobacter species, and K. pneumoniae infections persisted for the ciprofloxacin treatment failures. Infections by Enterobacter cloacae and Acinetobacter species persisted for the ceftazidime treatment failures. For UTI patients, E. coli was the organism most frequently isolated before treatment. All 14 UTI patients who completed treatment showed resolution or improvement. In the ciprofloxacin group two patients were superinfected by Enterococcus species, and in the ceftazidime group there were two superinfections by Enterococcus species and one by Enterobacter cloacae. Intravenous ciprofloxacin was as effective as ceftazidime in the treatment of nosocomial pneumonia and urinary tract infection. Caution should be exercised when treating serious infections by streptococci or staphylococci.

Multiple-dose pharmacokinetics of concurrent oral ciprofloxacin and rifampin therapy in elderly patients

The purpose of this clinical study was to investigate the influence of concomitant drug therapy with ciprofloxacin and rifampin on the individual pharmacokinetic profile of each agent in elderly patients. Twelve nursing home patients (age, 74 +/- 7 years), colonized with methicillin-resistant Staphylococcus aureus, were randomized to receive 14-day therapy with oral ciprofloxacin (750 mg every 12 h) (group A; n = 6) or ciprofloxacin (750 mg every 12 h) and oral rifampin (300 mg every 12 h) (group B; n = 6). Serial blood samples were obtained from 0 to 12 h following ciprofloxacin doses 1 and 13 and from 0 to 36 h after the last ciprofloxacin dose. No significant differences (P greater than 0.05) were found between or within groups in any pharmacokinetic parameter. The mean ciprofloxacin oral clearance values were 0.35 +/- 0.06, 0.41 +/- 0.15, and 0.38 +/- 0.11 liter/h per kg for doses 1, 13, and 28, respectively, in group A patients. The mean oral clearance values in group B patients for the respective doses were 0.53 +/- 0.36, 0.32 +/- 0.13, and 0.36 +/- 0.17 liter/h per kg. Likewise, no significant differences (P greater than 0.05) in rifampin pharmacokinetic parameters were found when compared with historical controls. These data suggest that ciprofloxacin and rifampin may be given concomitantly in standard clinical dosing regimens. The combination results in therapeutic levels of both drugs and appears to be safe for administration to elderly nursing home patients.

Patient-controlled analgesia: a review of effectiveness of therapy and an evaluation of currently available devices

Patient-controlled analgesia (PCA) is a major advance in the management of pain in postoperative and cancer patients. The success of PCA has resulted in a proliferation of marketed devices to administer small bolus doses of parenteral pain-control drugs at fixed intervals controlled by the patient with the push of a button. Because patients demonstrate marked individual variation in pain medication requirements, PCA devices should be able to accommodate rapidly changing requirements for drugs with a minimum amount of effort on behalf of health care personnel. Crude electronic devices were developed in the late 1960s and the early 1970s and usually consisted of a syringe pump connected to some sort of timing device. Most modern PCA devices marketed in the past five years are much more sophisticated devices that are microprocessor based and some newer devices even generate hard copy for a permanent record of drug administration. Although many such devices are available (including a totally disposable PCA device), few have undergone extensive clinical evaluation. A review of the literature shows many devices are available for use without a single publication to document the safety and utility of the device in the routine patient care situation. Use of the PCA method of pain control will grow, and all hospital-based health care personnel should become familiar with their use and limitations.

Comparison of urinary urea nitrogen excretion and measured energy expenditure in spinal cord injury and nonsteroid-treated severe head trauma patients

Severe head trauma patients (HT) exhibit markedly elevated energy expenditure and 24-hr urinary urea nitrogen excretion (UUN) values. The objective of this study was to compare seven spinal cord injured patients (SCI) to seven HT for changes in UUN and measured energy expenditure (MEE) over the first 18 days following injury. Energy expenditure was measured by indirect calorimetry and compared to values predicted by the Harris Benedict Equation (PEE). There were six quadriplegics and one paraplegic in the SCI group. HT patients had peak Glasgow Coma Scale scores of 3 to 10 for the first 24 hr postinjury. Patients were studied prospectively and matched for age, sex, and admitting weight Week 1 following the injury, SCI had mean UUN values of 0.18 +/- 0.04 g/kg/day vs 0.18 +/- 0.01 for HT patients. The mean MEE/PEE ratio was 0.56 for the SCI and 1.4 for HT (p less than 0.01). Over the entire study period the mean UUN value for SCI was 0.23 +/- 0.03 g/kg vs 0.21 +/- 0.01 for HT. The mean MEE/PEE ratio for SCI was 0.94 while HT remained elevated at 1.5 (p less than 0.05). Although the UUN was comparable in SCI vs HT, there was a significant difference in MEE/PEE between the groups. The elevation in UUN observed in SCI is not due to a hypermetabolic state. This suggests that different mechanisms promote the increased nitrogen excretion observed in these two populations.

Comparison of administration of two standard intravenous amino acid formulas to severely brain-injured patients

Twenty severely brain-injured patients with Glasgow Coma Scale scores of 4-9 were prospectively randomized to receive one of two standard amino acid formulas, starting with the first day of hospital admission up to day 14 postinjury. Formula 2 (patient group 2) had 54 percent more leucine, 53 percent more isoleucine, 74 percent more valine, 28 percent less phenylalanine, 31 percent less methionine, 111 percent more proline, 38 percent less alanine, and 38 percent less glycine than formula 1 (patient group 1). Groups 1 and 2 received statistically equal overall mean parenteral nutrition calories and protein (2173 +/- 147 vs. 2059 +/- 143 kcal, and 77 +/- 12 vs. 83.1 +/- 6 g, respectively). There was a significant difference in overall mean urinary urea nitrogen excretion (group 1 = 24.6 +/- 1.3 vs. group 2 = 18.3 +/- 1.1, p = 0.02) and nitrogen balance (group 1 = -8.0 +/- 2.1 vs. group 2 = +1.8 +/- 1.2, p = 0.01). Mean overall isoleucine values were significantly higher in group 2 (overall mean 77 mumol/L vs. 62 mumol/L, p = 0.04). Phenylalanine levels were significantly higher in group 1 (107 mumol/L) versus group 2 (82 mumol/L) patients (p = 0.01). Arginine levels were significantly higher in group 1 (78 mumol/L) versus group 2 (49 mumol/L) patients (p = 0.0002). This observation suggests that some standard intravenous amino acid formulas may be more apt to promote positive nitrogen balance than others.

Cost comparison of ceftazidime versus tobramycin/ticarcillin therapy in three hospitals

A retrospective review of 114 patient charts was conducted at three geographically different hospitals to compare the costs of ceftazidime (CTZ) with the combination of tobramycin and ticarcillin (T/T) in the treatment of hospital-acquired pneumonias and/or septicemias. Variables analyzed to determine the cost of the therapy included duration of treatment, dosage and number of doses administered, side effects, and laboratory tests. Time and motion studies were also performed and the results included in the algorithm. In two of the three hospitals, the computer-calculated cost of CTZ therapy was significantly less than for T/T therapy ($1194 vs. $1668 and $93 vs $629). In the third hospital there was no significant difference in the costs of the two treatments ($1079 for CTZ vs. $1066 for T/T). The cost of each regimen per patient day followed a similar pattern, with CTZ therapy being significantly less expensive in the same two hospitals. Patients receiving CTZ therapy realized an average cost savings of $29.70 per day at the three institutions. These savings appeared to be due to a reduction in laboratory and administration costs resulting from the decreased frequency of CTZ administration. We conclude that CTZ therapy was less costly than T/T therapy at three geographically different institutions when the cost of supplies, laboratory tests, and personnel time were taken into account.

Prophylactic parenteral antibiotics in clean neurosurgical procedures: a review

Clean surgical procedures carry a risk of postoperative wound infection that is less than 5% in most hospitals. The use of prophylactic antibiotic agents in clean neurosurgical cases is controversial, and the neurosurgical literature through 1980 contains no controlled clinical trials to study its effectiveness in such cases. A report of 1732 consecutive procedures without a single postoperative wound infection in patients receiving systemic gentamicin, vancomycin, and streptomycin irrigation fluids is often quoted by neurosurgeons; however, these results have not yet been duplicated by others. Since 1980, there have been several controlled trials that support the use in clean neurosurgical cases of prophylactic antibiotics, including the vancomycin/gentamicin/streptomycin regimen and the first-generation cephalosporins. A report in 1986 of 1602 cases without a primary wound infection supports the use of a single perioperative dose of cefazolin. A review of causative organisms in postoperative wound infections demonstrates the preponderance of Gram-positive pathogens. Therefore, when antibiotic prophylaxis is indicated, adequate Gram-positive bacterial coverage, including protection against Staphylococcus infection, is required. With consideration of the present data, the cost of antibiotic therapy, and the danger of drug toxicity, a short perioperative regimen of cefazolin as prophylaxis is preferred in clean neurosurgical cases.

Pentobarbital pharmacokinetics in patients with severe head injury

Intravenous administration of high-dose pentobarbital has been proposed as a treatment for elevated intracranial pressure refractory to other measures in brain-injured patients. The purpose of this clinical study was to examine the pharmacokinetics of high-dose continuous intravenous infusion of pentobarbital in this critical care setting. Six patients received a 25-34 mg/kg intravenous loading dose followed by a 1-3 mg/kg/h continuous infusion for 61-190 hours. Dosing rates were adjusted based on the patient's clinical status. The mean clearance was 0.72 ml/min/kg, with a volume of distribution (Vd) of 1.03 L/kg and a terminal half-life of 19.1 h. Considerable variation in individual patient parameters was observed. In addition, a change in clearance was suggested in patients requiring a longer infusion duration.

Evaluation of a disposable, nonelectronic, patient-controlled-analgesia device for postoperative pain

The safety and efficacy of a disposable, nonelectronic, patient-controlled-analgesia (PCA) device for alleviating postoperative pain were evaluated. Patients who were to undergo abdominal surgical procedures under general anesthesia were instructed in the use of the Travenol Infusor with Patient Control Module. Patients used the PCA device upon emerging from anesthesia in the recovery room. The PCA device delivered a 1-mg i.v. injection of morphine sulfate upon patient demand, with a relative delay of six minutes between allowable administrations. Nursing staff evaluated pain and sedation every four hours using a five-point scale. In the 50 patients evaluated, the highest analgesic use occurred during the first four to eight postoperative hours. After the immediate postoperative period, patients experienced either mild or no pain during approximately 90% of the evaluation periods. No patient suffered respiratory depression during self-dosing. Results of a poststudy self-assessment questionnaire showed that 90% of the patients reported experiencing mild to moderate pain overall, and 78% reported only mild discomfort throughout the postoperative period. Ninety-two percent of the patients strongly preferred PCA therapy over intramuscular injections. The Travenol Infusor with Patient Control Module represents a safe and effective device for PCA therapy of postoperative pain.