Effectively treating common infections in residents of long-term care facilities

Clinicians involved in caring for institutionalized elderly frequently must treat common infections endemic to the setting. Numerous factors specific to these patients make accurate diagnosis and management more difficult than in healthy ambulatory adults. Three infections are commonly encountered in residents of long-term care facilities: bacterial pneumonia, urinary tract infections, and skin and soft tissue infections. More antimicrobial agents are available now than ever before; therefore, judicious administration of drugs and familiarity with current treatment recommendations are imperative.

In vitro pharmacodynamic properties of MK-0991 determined by time-kill methods

MK-0991 has demonstrated activity against a variety of fungal pathogens. We evaluated the MIC endpoint for MK-0991 by reading the endpoint using three methods and comparing these results with minimum fungicidal concentrations and electron micrographs. The concentration that resulted in 80% inhibition of fungal growth compared with control, similar to the endpoint for the azole antifungal agents, provided the most consistent results. Additionally, we investigated the time-kill properties of this agent against two isolates each of Candida albicans, Candida glabrata and Candida tropicalis at concentrations ranging from 0.125 x MIC to 16 x MIC. Kill curves were performed using RPMI buffered with morpholine propanesulfonic acid as growth media. Samples were obtained at predetermined time points over 24 h and plated for colony counting. Fungicidal activity was observed with one isolate of C. albicans, two isolates of C. glabrata, and one isolate of C. tropicalis. MK-0991 displayed concentration-dependent activity, which was fungicidal or fungistatic depending on the isolate tested.

Oral corticosteroids for pain associated with herpes zoster

It is apparent from published studies that corticosteroids do not prevent the development of postherpetic neuralgia. Earlier trials that indicated some benefit in both acute neuralgia and the prevention of postherpetic neuralgia are of limited use to clinicians due to problems with uncontrolled study designs, small sample sizes, and the absence of statistical analysis of the results. The lack of a consensus definition of postherpetic neuralgia, the variable agents and dosages used, and the different pain scales reported are of concern when trying to interpret the results of these studies for their clinical significance. In more recent larger and well-designed studies, similar rates of postherpetic neuralgia were observed in the corticosteroid and control groups. As a result of these findings, corticosteroids should not be recommended for the prevention of postherpetic neuralgia. Despite lack of efficacy in preventing postherpetic neuralgia, limited studies suggest corticosteroids such as prednisone (40-60 mg/d tapered over 3 wk) are well tolerated and may confer slightly significant benefits in reducing the duration of acute neuralgia and improving quality-of-life measures. However, the clinical significance and application of these findings remain to be addressed. If corticosteroids are used for acute neuralgia, clinicians are advised to select their patients carefully. The patients treated in these studies were generally healthy and free of comorbid diseases, such as hypertension, diabetes mellitus, and psychiatric disorders, which can be exacerbated in the presence of corticosteroids. Although dissemination of herpes zoster has been reported infrequently, it remains a potential risk with use of corticosteroids. Until the results of these studies are repeated in more diverse patient populations, corticosteroids appear to have a limited role in the management of acute neuralgia associated with herpes zoster.

Evaluation of endpoints for antifungal susceptibility determinations with LY303366

We have previously reported poor correlation between the in vitro fungicidal activity of LY303366 and MIC results in RPMI medium based upon the manufacturer's suggested susceptibility endpoint, lack of visual growth. Additionally, we have noted a significant trailing effect with LY303366 when MICs are determined in RPMI medium. These observations have led us to evaluate an alternative susceptibility endpoint for LY303366, an 80% reduction in growth compared with control (similar to that utilized for azoles). Two isolates each of Candida albicans, Candida glabrata, and Candida tropicalis were selected for testing. MICs were determined for LY303366 in RPMI 1640 medium buffered with morpholinepropanesulfonic acid. MICs were determined with suggested (MIC100) and experimental (MIC80) endpoints. The minimal fungicidal concentration (MFC) of LY303366 for each isolate was also determined. Time-kill curves were determined in RPMI medium with each isolate at concentrations of LY303366 ranging from 0.125 to 16x MIC80 to assess the correlation between MIC80 and fungicidal activity. Lastly, fungi exposed to LY303366 were examined via scanning electron microscope (SEM) for evidence of drug-induced ultrastructure change. MIC80s for test isolates ranged from 0.015 to 0.12 microgram/ml and were consistently three to five wells less than MIC100s. Good correlation was observed between fungicidal activity, as assessed by kill curves, and the MIC80. SEM data revealed significant ultrastructure changes induced by LY303366 even at sub-MIC80s. Based on our results demonstrating better correlation between MIC80 and fungicidal activity, i.e., time-kill curves and MFCs, we suggest that 80% reduction in visible growth be utilized as the endpoint for susceptibility determinations with LY303366 in RPMI medium.

Mibefradil, a pharmacologically distinct calcium antagonist

Mibefradil is the prototype of a new class of calcium antagonists that selectively block T-type voltage-gated plasma membrane calcium channels in vascular smooth muscle. The drug is structurally and pharmacologically different from traditional calcium antagonists. It does not have negative inotropism at therapeutic concentrations, and is not associated with reflex activation of neurohormonal and sympathetic systems. In clinical studies of hypertension, mibefradil 50 and 100 mg/day reduced trough sitting diastolic and systolic blood pressures in a dose-related manner. Dosages exceeding 100 mg/day generally did not result in significantly greater efficacy, but were associated with a higher frequency of adverse events. No first-dose hypotensive phenomenon was observed. Mibefradil has antiischemic properties resulting from dilation of coronary and peripheral vascular smooth muscle, and a slight reduction in heart rate. In clinical studies of chronic stable angina pectoris, dose-related increases in exercise duration, time to onset of angina, and time to 1-mm ST-segment depression during exercise tolerance tests occurred. Mibefradil reduced the number and duration of ischemic events recorded by 48-hour ambulatory electrocardiograph (ECG) monitoring, as well as number of anginal episodes and nitroglycerin consumption. Favorable hemodynamic and clinical profiles are reported, including high trough:peak ratios (> 80%), high oral bioavailability, and long elimination half-life (17-25 hrs) permitting once/day dosing. Dizziness, headache, leg edema, and lightheadedness are frequently reported, but overall the agent is well tolerated. First-degree atrioventricular block and sinus bradycardia are the most frequent ECG changes caused by the drug. In vitro studies indicate mibefradil inhibits cytochrome P450 1A2, 2D6, and 3A4, resulting in elevated plasma concentrations of drugs metabolized by those isoenzymes. Therefore, it is contraindicated in patients receiving terfenadine, astemizole, cisapride, lovastatin, or simvastatin.

Influence of test conditions on antifungal time-kill curve results: proposal for standardized methods

This study was designed to examine the effects of antifungal carryover, agitation, and starting inoculum on the results of time-kill tests conducted with various Candida species. Two isolates each of Candida albicans, Candida tropicalis, and Candida glabrata were utilized. Test antifungal agents included fluconazole, amphotericin B, and LY303366. Time-kill tests were conducted in RPMI 1640 medium buffered with morpholinepropanesulfonic acid (MOPS) to a pH of 7.0 and incubated at 35 degrees C. Prior to testing, the existence of antifungal carryover was evaluated at antifungal concentrations ranging from 1x to 16x MIC by four plating methods: direct plating of 10, 30, and 100 microl of test suspension and filtration of 30 microl of test suspension through a 0.45-microm-pore-size filter. Time-kill curves were performed with each isolate at drug concentrations equal to 2 x MIC, using a starting inoculum of approximately 10(5) CFU/ml, and incubated with or without agitation. Last, inoculum experiments were conducted over three ranges of starting inocula: 5 x 10(2) to 1 x 10(4), >1 x 10(4) to 1 x 10(6), and >1 x 10(6) to 1 x 10(8) CFU/ml. Significant antifungal carryover (>25% reduction in CFU/milliliter from the control value) was observed with amphotericin B and fluconazole; however, carryover was eliminated with filtration. Agitation did not appreciably affect results. The starting inoculum did not significantly affect the activity of fluconazole or amphotericin B; however, the activity of LY303366 may be influenced by the starting inoculum. Before antifungal time-kill curve methods are routinely employed by investigators, methodology should be scrutinized and standardized procedures should be developed.

Acyclovir- and ganciclovir-induced neurotoxicity

With increasing use of acyclovir and ganciclovir, primarily due to the increased number of AIDS and transplant patients, further cases of neurologic toxicity will undoubtedly be encountered. Discontinuation or dosage reduction of acyclovir and ganciclovir is necessary to manage neurologic toxicity that is directly attributed to either agent. Renal dysfunction is a known risk factor for acyclovir neurotoxicity, and case reports indicate that renal dysfunction may also be a risk factor for ganciclovir neurotoxicity. Since ganciclovir is structurally related to acyclovir, clinicians should monitor for signs and symptoms of neurotoxicity as they would with acyclovir until the risk factors are more clearly defined. Dosage reduction for both agents and increased monitoring should occur when renal dysfunction is present, to minimize the risk of neurotoxicity and other serious adverse effects. Tables 1 and 2 summarize the recommended dosages of acyclovir and ganciclovir, respectively, in the presence of renal dysfunction. However, as a few case reports describe, neurotoxicity from these agents has also occurred in patients with normal renal function. Therefore, clinicians should always remain vigilant in monitoring for signs of neurotoxicity when acyclovir or ganciclovir is administered, and have a high index of suspicion for these agents if neurotoxicity is encountered during therapy.

Growth medium effect on the antifungal activity of LY 303366

The impact of growth medium selection on antifungal susceptibility testing has been well documented. Previously we described the antifungal characteristics of LY 303366 via time-kill curve methods using RPMI 1640 buffered with 0.165 M morpholinepropane-sulfonic acid as growth medium. The purpose of the current study was to compare the previously reported kill curve results with results obtained using antibiotic medium number three (AM #3) as growth medium. Antifungal activity was assessed via susceptibility testing and time-kill studies in both media. Two isolates each of Candida albicans, C. glabrata, and C. tropicalis were studied. MICs for the six isolates were found to be 10 to 100 times lower in AM #3. Time-kill studies were conducted with multiples of the MIC ranging from 0.125 x MIC to 16 x MIC. LY 303366 exhibited fungicidal (> or = 3 log10 reduction in CFU) activity against all isolates in AM #3; however, fungicidal activity was noted only for three of the six isolates when tested in RPMI. Furthermore, the rate of fungicidal activity was more rapid when AM #3 was utilized. Not only were the rate and extent of activity influenced by choice of media, but the relationships between LY 303366 concentrations and activity were also found to be media dependent. The findings from this study serve to highlight further the importance of media selection for in vitro evaluation of antifungal activity. In vivo studies need to be conducted with LY 303366 to determine which media provides the best correlation between in vitro and in vivo findings.

Tetanus: pathophysiology and management

OBJECTIVE

To review the epidemiology, pathophysiology, clinical manifestations, diagnosis, and management of tetanus and its complications.

DATA SOURCES

MEDLINE and Iowa Drug Information Services databases were searched for literature pertaining to tetanus. Additional literature was obtained from the references of selected articles identified in the search. Information from all articles was considered for inclusion in the manuscript.

STUDY SELECTION AND DATA EXTRACTION

Articles selected were those considered by the authors to assist in providing the reader an understanding of the epidemiology, pathophysiology, clinical manifestations, diagnosis, and management of tetanus.

DATA SYNTHESIS

While the number of tetanus cases has decreased markedly since data reporting for the disease began in 1947, mortality among those who acquire the disease remains high. Elderly patients are particularly susceptible to tetanus and its complications. Prevention of tetanus focuses on primary immunization and scheduled boosters. Management of tetanus involves initial stabilization of the patient and protection of the airway, prevention of tetanospasmin absorption by administration of human tetanus immune globulin 3000-6000 IU, and eradication of Clostridium tetani with antimicrobial therapy (metronidazole 500 mg q8h). Supportive measures include the administration of neuromuscular blocking agents such as pancuronium in patients requiring artificial ventilation, as well as benzodiazepines (midazolam 5-15 mg/h) for sedation and muscle relaxation. Autonomic dysfunction should be managed with beta-adrenergic blockers such as propranolol or labetalol.

CONCLUSIONS

Despite the relative infrequency of tetanus cases, mortality among untreated patients remains significantly high. Clinicians should become knowledgeable in the pathophysiology, clinical manifestations, and management of this potentially fatal disease.

Levofloxacin and trovafloxacin: the next generation of fluoroquinolones?

The pharmacology, spectrum of activity, pharmacokinetics, clinical efficacy, and adverse effects of levofloxacin, recently approved by FDA, and trovafloxacin, currently undergoing clinical trials, are reviewed. Compared with quinolones in current use, levofloxacin is more potent against gram-negative bacteria and exhibits better antipseudomonal activity as well as greater oral bioavailability. Trovafloxacin is more potent than existing quinolones against gram-positive bacteria. Both agents exert their antibacterial effects by inhibiting bacterial DNA synthesis. Compared with other quinolones, levofloxacin and trovafloxacin both demonstrate superior activity against the Bacteroides fragilis group, Chlamydia spp., Mycoplasma pneumoniae, and Mycobacterium spp. The half-life (t1/2) of levofloxacin is nearly eight hours. Levofloxacin can therefore be administered once daily for mild to moderate infections and twice daily for more serious infections. The recommended daily dose is 500 mg. Trovafloxacin has a t1/2 of 12 hours, which allows for single daily doses, and is extensively metabolized. Levofloxacin has demonstrated clinical efficacy in the treatment of community-acquired respiratory-tract infections, genitourinary infections, skin and skin-structure infections, acute bacterial sinusitis, and infections of the head and neck. Trovafloxacin may have a role in treating skin and skin-structure or soft-tissue infections respiratory-tract infections, sexually transmitted diseases, and meningitis. Both agents are well tolerated, with central-nervous-system and gastrointestinal adverse effects reported most frequently. Concomitant administration of antacids or compounds containing meal cations decreases absorption of these quinolones. Levofloxacin and trovafloxacin have favorable antimicrobial and pharmacokinetic profiles, offering the advantages of once-daily doses as well as superior potency and spectrum of activity compared with currently available quinolones.

Reevaluating the Safety of Concurrent Warfarin and Ibuprofen Therapy: A Case Report

Objective:

To describe a case of subclinical bleeding and elevated international normalized ratio (INR) associated with the concomitant use of ibuprofen and warfarin.

Case Summary:

A 74-year-old white woman receiving warfarin for a history of cerebrovascular accident and deep-vein thrombosis with concomitant chronic obstructive pulmonary disease, hypertension, congestive heart failure, coronary artery disease, osteoarthritis, and erosive esophagitis developed significant elevation of the INR after the addition of ibuprofen to her medication regimen. The patient experienced a decrease in hemoglobin concentration, asymptomatic hypotension, and increased blood urea nitrogen/creatinine ratio. Limited physical examination failed to locate a source of bleeding.

Discussion:

The pharmacokinetic and pharmacodynamic interactions involving nonsteroidal antiinflammatory agents and warfarin are well documented. Limited data from healthy volunteers and patients without complex medical problems suggest that ibuprofen and warfarin may be given concomitantly with relative safety. This report describes an elderly patient with multiple medical problems, treated with numerous medications, including warfarin, who developed signs suggestive of subclinical bleeding and an INR of 14.3 after the addition of low-dose ibuprofen.

Conclusions:

Concomitant use of ibuprofen and warfarin should be avoided in elderly patients with complex medical problems treated with multiple medications.

Implementation of a community pharmacy-based influenza vaccination program

OBJECTIVE

To increase accessibility of influenza vaccine in a rural community by establishing a community pharmacy-based influenza vaccination program.

SETTING

An independent pharmacy in a rural eastern Iowa community of 5,000 people.

PRACTICE DESCRIPTION

Protocols for identification and screening of patients, administration of vaccine, and treatment of emergencies were developed by the pharmacist and approved by the county health department medical director. Administration of vaccine began October 15, 1996, and was completed on December 6, 1996.

PRACTICE INNOVATION

Patients were prospectively and retrospectively identified to receive the vaccination. Informed consent was obtained. Vaccine was administered by the pharmacist after screening for contraindications and counseling the patient. Weekly vaccination records were forwarded to the collaborating physician to update patient charts.

MAIN OUTCOME MEASUREMENTS

To determine whether accessibility of influenza vaccine in the community was increased through pharmacist administration, the proportion of patients immunized in the pharmacy who were not vaccinated the previous year was determined.

RESULTS

The pharmacist administered 343 doses of vaccine. Two-thirds of the immunized patients (67.9%) reported also being immunized the previous year. These patients were generally older (65 years of age +/- 13) than the previously nonimmunized patients (54 years of age +/- 16). However, 60.8% of the patients not immunized the previous year reported either they would not have gone elsewhere for the immunization (45.3%), or were unsure (25.5%).

CONCLUSION

The data collected suggest that pharmacist administration of influenza vaccination in a rural community pharmacy increases access and, possibly, immunization rates. This may be especially true among high-risk younger adults who are often overlooked and would not normally have received the immunization.

Antifungal dynamics of LY 303366, an investigational echinocandin B analog, against Candida ssp

Two isolates each of Candida albicans, Candida tropicalis, and Candida glabrata were selected for time-kill curve testing against LY 303366 at concentrations ranging from 0.125 x MIC to 16 x MIC. RPMI 1640 buffered morpholinepropanesulfonic acid (MOPS) was utilized as growth medium. Samples were obtained at predetermined time points over 24 hours and streaked for colony count determination. Against C. albicans (one strain) and C. glabrata isolates, LY 303366 exhibited fungicidal (> or = three log10 reduction in CFU) activity. In contrast, fungistatic activity was observed with LY 303366 against C. albicans (one strain) and C. tropicalis isolates at all of the multiples of the MIC tested. With the exception of one C. glabrata strain, the rate and extent of activity against test isolates was not enhanced with concentrations exceeding the MIC. Our data indicate that maximal antifungal activity with LY 303366 may be achieved by optimizing the time of fungal exposure to the drug. Additionally, these data suggest that use of the current interpretive endpoint for MICs in RPMI may underestimate the antifungal activity of LY 303366. Thus, the MIC endpoint may need to be re-evaluated, or perhaps an alternative media, such as antibiotic medium #3, should be utilized for determination of LY 303366 MICs.