Oral erythromycin and the risk of sudden death from cardiac causes

Assessment of potential drug–drug interactions with a prescription claims database

PURPOSE

The prevalence of 25 clinically important potential drug-drug interactions (DDIs) in a population represented by the drug claims database of a pharmacy benefit management company (PBM) was studied.

METHODS

A retrospective cross-sectional analysis of pharmaceutical claims for almost 46 million participants in a PBM was conducted to determine the frequency of 25 DDIs previously identified as clinically important. A DDI was counted when drugs in potentially interacting combinations were dispensed within 30 days of each other during a 25-month period between April 2000 and June 2002.

RESULTS

The number of DDIs ranged from 37 for pimozide and an azole antifungal to 127,684 for warfarin and a nonsteroidal antiinflammatory drug (NSAID). The highest prevalence (278.56 per 100,000 persons) and highest case-exposure rate (242.7 per 1,000 warfarin recipients) occurred with the warfarin-NSAID combination. The combination with the lowest overall prevalence (cyclosporine and a rifamycin, 0.10/100,000) differed from the combination with the lowest case-exposure rate (pimozide and an azole antifungal, 0.028 per 1,000 azole antifungal recipients). Number of cases, prevalence, and case-exposure rates for both sexes generally increased with age. An estimated 374,000 plan participants were exposed to a clinically important DDI during a 25-month period. Between 20% and 46% of prescription drug claims were reversed (canceled) for a medication with a drug interaction when a warning about the interaction was sent to the pharmacy.

CONCLUSION

Analysis of prescription claims data from a major PBM found that 374,000 of 46 million plan participants had been exposed to a potential DDI of clinical importance.

Torsade de pointes in a patient with complex medical and psychiatric conditions receiving low-dose quetiapine

OBJECTIVE

Describe potential cardiac complications of low-dose quetiapine and other atypical antipsychotic drugs.

METHOD

We present a case report of a 45-year-old Black woman with multiple medical and psychiatric problems taking low-dose quetiapine.

RESULTS

Coincident with a generalized seizure, the patient developed 'ventricular fibrillation'. She was countershocked with restoration of normal sinus rhythm. The initial electrocardiogram showed QT interval prolongation. Shortly thereafter, classical torsade de pointes appeared, lasted 10 min, and resolved spontaneously. Hypomagnesemia was present. A cardiac electrophysiologist was concerned that the very slow shortening of the prolonged QTc interval after magnesium replacement implicated quetiapine as a risk factor for QTc interval prolongation and torsade de pointes. A psychosomatic medicine consultant asserted that the fragmented medical and psychiatric care almost certainly contributed to the patient's medical problems. We discuss other cases of QT interval prolongation by newer antipsychotic drugs and previous reports by our group concerning the association of psychotropic drugs, QT interval prolongation, and torsade de pointes.

CONCLUSION

Atypical antipsychotic drug administration, when accompanied by risk factors, may contribute to cardiac arrhythmias including torsade de pointes.

Efficacy and safety of a novel, single-dose azithromycin microsphere formulation versus 10 days of levofloxacin for the treatment of acute bacterial sinusitis in adults

OBJECTIVE

To compare the efficacy and safety of a single 2.0-g dose of a novel azithromycin microsphere formulation with that of 10 days of levofloxacin, 500 mg/d, when used to treat adults with uncomplicated acute bacterial maxillary sinusitis (ABS).

STUDY DESIGN AND SETTING

An international, multicenter, randomized, double-blind, double-dummy trial. Eligible outpatients > or =18 years of age with clinical and radiographic evidence of ABS underwent maxillary sinus aspiration before randomization. Primary endpoint was clinical efficacy at the test-of-cure visit (day 17-24).

RESULTS

Clinical success rates were 94.5% (242/256) in azithromycin-microspheres-treated patients and 92.8% (233/251) in the levofloxacin group. In patients with documented Streptococcus pneumoniae, Haemophilus influenzae, or Moraxella catarrhalis, clinical cure rates were 97.3% (36/37), 96.3% (26/27), and 100% (8/8), respectively, for the azithromycin group and 92.3% (36/39), 100% (30/30), and 90.9% (10/11), respectively, for the levofloxacin group.

CONCLUSIONS

Single-dose azithromycin microspheres provided clinical and bacteriologic efficacy and safety comparable to 10 days of levofloxacin.

SIGNIFICANCE

A novel microsphere formulation of azithromycin given as a single dose was safe and effective for the treatment of ABS.

Fatal Interaction between Clarithromycin and Colchicine in Patients with Renal Insufficiency: A Retrospective Study

BACKGROUND

Clarithromycin is frequently used to treat community-acquired pneumonia in elderly persons. Like erythromycin, it may interact with other drugs by interfering with metabolism by cytochrome P450 enzymes and with the P-glycoprotein transporter system. Colchicine, used for treatment of acute gout and for prophylaxis, may cause bone marrow toxicity. It is metabolized by CYP3A4 and is transported by P-glycoprotein. Initial case reports suggested potentially fatal interactions between clarithromycin and colchicine.

METHODS

A retrospective study was conducted with 116 patients who were prescribed clarithromycin and colchicine during the same clinical admission. Case-control comparisons were made between patients who received concomitant therapy with the 2 drugs and patients who received sequential therapy. We assessed the clinical presentations and outcomes of the 2 patient groups and analyzed the risk factors associated with fatal outcomes.

RESULTS

Nine (10.2%) of the 88 patients who received the 2 drugs concomitantly died. Only 1 (3.6%) of the 28 patients who received the drugs sequentially died. Multivariate analysis of the 88 patients who received concomitant therapy showed that longer overlapped therapy (relative risk [RR], 2.16; 95% confidence interval [CI], 1.41-3.31; P< or =.01), the presence of baseline renal impairment (RR, 9.1; 95% CI, 1.75-47.06; P<.001), and the development of pancytopenia (RR, 23.4; 95% CI, 4.48-122.7; P<.001) were independently associated with death.

CONCLUSIONS

Clarithromycin increases the risk of fatal colchicine toxicity, especially for patients with renal insufficiency. Since there are other drugs for treatment of pneumonia and gout, these 2 drugs should not be coprescribed, because of the risk of fatality.

Antimicrobial treatment of lower respiratory tract infections in the hospital setting

Respiratory tract infections (RTIs) that may require hospitalization include acute exacerbations of chronic bronchitis (AECB), community-acquired pneumonia (CAP), and hospital-acquired pneumonia (HAP), which includes ventilator-associated pneumonia (VAP). Healthcare-associated pneumonia (HCAP) is treated similar to HAP and may be considered with HAP. For CAP requiring hospitalization, the current guidelines for the treatments of RTIs generally recommend either a beta-lactam and macrolide combination or a fluoroquinolone. The respiratory fluoroquinolones (levofloxacin, gatifloxacin, moxifloxacin, and gemifloxacin) are excellent antibiotics due to high levels of susceptibility among gram-negative, gram-positive, and atypical pathogens. The fluoroquinolones are active against > 98% of Streptococcus pneumoniae, including penicillin-resistant strains. Fluoroquinolones are also recommended for AECB requiring hospitalization. Evidence from clinical trials suggests that levofloxacin monotherapy is as efficacious as combination ceftriaxone-erythromycin therapy in the treatment of patients hospitalized with CAP. For early-onset HAP, VAP, and HCAP without the risk of multidrug resistance, ceftriaxone, ampicillin-sulbactam, ertapenem, or one of the fluoroquinolones is recommended. High-dose, short-course therapy regimens may offer improved treatment due to higher drug concentrations, more rapid killing, increased adherence, and the potential to reduce development of resistance. Recent studies have shown that short-course therapy with levofloxacin, azithromycin, or telithromycin in patients with CAP was effective, safe, and tolerable and may control the rate of resistance.

Dentistry and endocarditis

Bacterial endocarditis (BE), a rare heart infection caused by a bacteremia, has frequently been blamed on but rarely caused by dental procedures. Viridans group streptococci are found abundantly in the mouth and the gingival sulcus but have been surpassed by staphylococci as the leading cause of BE. Antibiotic prophylaxis has been recommended before dental procedures in patients at risk for BE, but it remains controversial because studies have failed to show that antibiotic prophylaxis is an effective preventive for BE or that dental procedures are an important cause of BE. The risks and costs of antibiotic prophylaxis, including antibiotic resistance, cross-reactions with other drugs, allergy, anaphylaxis, and even death, may exceed the benefits in preventing BE. The rationale for the use of antibiotic prophylaxis to prevent BE allegedly caused by dental procedure bacteremias must be seriously reexamined based on recent evidence, particularly the absolute risk rates for endocarditis after a given dental procedure.

Non-cardiac QTc-prolonging drugs and the risk of sudden cardiac death

AIMS

To assess the association between the use of non-cardiac QTc-prolonging drugs and the risk of sudden cardiac death.

METHODS AND RESULTS

A population-based case-control study was performed in the Integrated Primary Care Information (IPCI) project, a longitudinal observational database with complete medical records from more than 500,000 persons. All deaths between 1 January 1995 and 1 September 2003 were reviewed. Sudden cardiac death was classified based on the time between onset of cardiovascular symptoms and death. For each case, up to 10 random controls were matched for age, gender, date of sudden death, and general practice. The exposure of interest was the use of non-cardiac QTc-prolonging drugs. Exposure at the index date was categorized into three mutually exclusive groups of current use, past use, and non-use. The study population comprised 775 cases of sudden cardiac death and 6297 matched controls. Current use of any non-cardiac QTc-prolonging drug was associated with a significantly increased risk of sudden cardiac death (adjusted OR: 2.7; 95% CI: 1.6-4.7). The risk of death was highest in women and in recent starters.

CONCLUSION

The use of non-cardiac QTc-prolonging drugs in a general population is associated with an increased risk of sudden cardiac death.

New advances in antibiotic development and discovery

The development of new antibiotics is crucial to controlling current and future infectious diseases caused by antibiotic-resistant bacteria. Increased development costs, the difficulty in identifying new drug classes, unanticipated drug toxicities, the ease by which bacteria develop resistance to new antibiotics and the failure of many agents to address antibiotic resistance specifically, however, have all led to an overall decline in the number of antibiotics that are being introduced into clinical practice. Although there are few, if any, advances likely in the immediate future, there are agents in both clinical and preclinical development that can address some of the concerns of the infectious disease community. Many of these antibiotics will be tailored to specific infections caused by a relatively modest number of susceptible and resistant organisms.

Unique aspects of antimicrobial use in older adults

Elderly persons consume a significant proportion of health care resources. Antimicrobials are just one class among many pharmaceuticals that are prescribed more frequently to elderly patients than to younger patients. There are unique aspects of antimicrobial use in elderly persons that make prescribing complicated and monitoring unpredictable. Physiologic changes associated with aging result in altered pharmacokinetics, and accurate estimates of renal function cannot be made with standard methods. Together, these qualities make antimicrobial dosing difficult. Because of a higher prevalence of other chronic diseases, there is a greater propensity for polypharmacy and a resulting risk of an adverse event or a significant drug interaction. Lastly, irrespective of altered pharmacokinetics, adverse effects of many antimicrobials are more common in elderly persons, which introduces an added dimension to ensuring safety with antimicrobial therapy.

Risk of acute myocardial infarction and sudden cardiac death in patients treated with cyclo-oxygenase 2 selective and non-selective non-steroidal anti-inflammatory drugs: nested case-control study

BACKGROUND

Controversy has surrounded the question about whether high-dose rofecoxib increases or naproxen decreases the risk of serious coronary heart disease. We sought to establish if risk was enhanced with rofecoxib at either high or standard doses compared with remote non-steroidal anti-inflammatory drug (NSAID) use or celecoxib use, because celecoxib was the most common alternative to rofecoxib.

METHODS

We used data from Kaiser Permanente in California to assemble a cohort of all patients age 18-84 years treated with a NSAID between Jan 1, 1999, and Dec 31, 2001, within which we did a nested case-control study. Cases of serious coronary heart disease (acute myocardial infarction and sudden cardiac death) were risk-set matched with four controls for age, sex, and health plan region. Current exposure to cyclo-oxygenase 2 selective and non-selective NSAIDs was compared with remote exposure to any NSAID, and rofecoxib was compared with celecoxib.

FINDINGS

During 2302029 person-years of follow-up, 8143 cases of serious coronary heart disease occurred, of which 2210 (27.1%) were fatal. Multivariate adjusted odds ratios versus celecoxib were: for rofecoxib (all doses), 1.59 (95% CI 1.10-2.32, p=0.015); for rofecoxib 25 mg/day or less, 1.47 (0.99-2.17, p=0.054); and for rofecoxib greater than 25 mg/day, 3.58 (1.27-10.11, p=0.016). For naproxen versus remote NSAID use the adjusted odds ratio was 1.14 (1.00-1.30, p=0.05).

INTERPRETATION

Rofecoxib use increases the risk of serious coronary heart disease compared with celecoxib use. Naproxen use does not protect against serious coronary heart disease.

An economic and outcomes assessment of first-line monotherapy in the treatment of community-acquired pneumonia within managed care

OBJECTIVE

To evaluate the resource consumption and outcomes associated with first-line monotherapy for community-acquired pneumonia, focusing specifically on the use of erythromycin, azithromycin, clarithromycin, and levofloxacin.

STUDY DESIGN

Retrospective managed care database analysis.

PATIENTS AND METHODS

Subjects included patients within a managed care setting over 18 years of age with an initial diagnosis of community-acquired pneumonia from January 1995 to April 2002. Multivariate linear and logistic regression models were used to examine associations with treatment success rates and direct medical costs between antibiotic treatments after controlling for patient demographics and pneumonia risk factors.

MAIN RESULTS

Overall, treatment success rates were high (95.8%), the use of second antibiotics was un common (2.3%), and hospitalizations were infrequent (2.0%) among the 1952 subjects studied. After controlling for patient characteristics and risk factors, significantly lower total costs were associated with erythromycin (92.7% lower, p < 0.001), azithromycin (48.7% lower, p < 0.001), and clarithromycin (21.3% lower, p = 0.015) relative to levofloxacin, with no difference in treatment success between groups. Among newer agents, azithromycin (49.2% lower, p < 0.001) and clarithromycin (21.7% lower, p = 0.013) treatment groups were associated with significantly lower total costs than levofloxacin in the full sample. However, in subjects with a chronic disease score above the sample's mean, only azithromycin was associated with significantly lower total costs (47.9% lower, p < 0.001) relative to levofloxacin.

CONCLUSION

Erythromycin, azithromycin, and clarithromycin were associated with significantly lower total costs than levofloxacin, although treatment success rates did not differ between groups. Following stratification based upon various subset criteria, erythromycin and azithromycin were observed to have significantly lower total costs than levofloxacin. Although these findings may augment clinical guidelines and evidence-based approaches, health plans should consider evaluating their own patient data to see if similar differences exist in their populations.

Alternative medical treatment strategies for chronic hyperplastic eosinophilic sinusitis

PURPOSE OF REVIEW

Chronic rhinosinusitis (CRS) is one of the most common chronic illnesses in the United States. Although CRS has been viewed traditionally as an infectious disease, treatment focused on antibiotics and surgery has not infrequently provided disappointing results.

RECENT FINDINGS

Recently much of CRS has been shown to be an eosinophilic inflammatory disease and new anti-inflammatory treatments are being studied.

SUMMARY

This review discusses medical management for chronic hyperplastic eosinophilic sinusitis, including antifungal treatment, low-dose macrolide treatment, antilipid mediator therapy, and new immune-modifying treatments.

Verapamil Toxicity Resulting from a Probable Interaction with Telithromycin

OBJECTIVE:

To report a case of hypotension and bradyarrhythmia caused by verapamil toxicity in a patient prescribed telithromycin.

CASE SUMMARY:

A 76-year-old white woman receiving verapamil 180 mg/day for hypertension experienced a sudden onset of shortness of breath and weakness and was found to be profoundly hypotensive and bradycardic, with a systolic blood pressure of 50–60 mm Hg and a heart rate of 30 beats/min. She had been taking telithromycin 800 mg/day for 2 days previously for acute sinusitis. The patient was treated with crystalloids, vasopressors, and transvenous pacing. Approximately 72 hours after admission, her blood pressure and heart rate rapidly returned to normal, and she was discharged several days later.

DISCUSSION:

Telithromycin is a known substrate of the CYP3A4 system, and several pharmacokinetic interactions can occur by displacement of other drugs from this system. Verapamil is metabolized through several cytochrome P450 isoenzyme systems. Although there are no previous reports of an interaction between these drugs, other possible causes for the patient's symptoms were excluded and the diagnosis of a probable interaction between verapamil and telithromycin leading to verapamil toxicity was made.

CONCLUSIONS:

Telithromycin is a ketolide antibiotic approved for treatment of respiratory tract infections and acute sinusitis. The potential for clinically significant drug interactions should be considered before using this agent, especially in patients taking other drugs that are metabolized through the CYP3A system. Caution should be exercised when considering the use of this antibiotic in patients receiving verapamil.

QTc prolongation associated with combination therapy of levofloxacin, imipramine, and fluoxetine

OBJECTIVE

To report QTc interval prolongation associated with combination therapy including levofloxacin, imipramine, and fluoxetine.

CASE SUMMARY

A 49-year-old white female presented to the emergency department with fever, aches, and pains for the past 3 days. She was diagnosed and treated for pyelonephritis in the hospital. Therapy included intravenous levofloxacin 500 mg every 24 hours and ceftriaxone 2 g every 24 hours, along with her medications upon admission, including imipramine 50 mg at bedtime and fluoxetine 10 mg/day. She was discharged after 5 days and returned the next day with chest tightness and shortness of breath. Upon the second admission, a 12-lead electrocardiogram showed a QTc interval of 509 msec. Levofloxacin was discontinued and the QTc interval fell to 403 msec. The patient was discharged 3 days later and instructed to consult with her primary care physician about discontinuing imipramine.

DISCUSSION

This adverse drug reaction is thought to be a pharmacodynamic additive effect among fluoxetine, imipramine, and levofloxacin. Fluoxetine is a potent inhibitor of CYP2D6, and imipramine is metabolized by CYP2D6. Therefore, fluoxetine is able to increase the plasma concentrations of imipramine, leading to QT interval prolongation. Taken with imipramine, levofloxacin can lead to even greater prolongation of the QT interval. Based on the Naranjo probability scale, levofloxacin was possibly associated with cardiac arrhythmias in our patient.

CONCLUSIONS

The use of levofloxacin alone, or more often in concomitant therapy with other medications that are known to prolong the QT interval, may cause QT interval prolongation; however, additional studies/case reports are needed to validate this conclusion.