Pharmacokinetics and inflammatory fluid penetration of intravenous daptomycin in volunteers

Gram-positive resistance: pathogens, implications, and treatment options: insights from the Society of Infectious Diseases Pharmacists

Despite the advent of new antibiotics, resistance in gram-positive pathogens, including staphylococci and enterococci, continues to increase. This is evident with the recent emergence of vancomycin-resistant Staphylococcus aureus . Newer treatment agents are available, including quinupristin-dalfopristin, linezolid, and daptomycin. In addition, investigational agents are being explored. Clinical trials have been conducted for various infections, such as skin and skin structure infections, pneumonia, and bloodstream infections. Antibacterial activity, site of infection, and potential for adverse effects must be taken into account when making decisions regarding therapy.

Daptomycin: a novel cyclic lipopeptide antimicrobial

PURPOSE

The development, activity, pharmacokinetics, pharmacodynamics, clinical efficacy, adverse effects, and dosage and administration of daptomycin are reviewed.

SUMMARY

Daptomycin, a novel cyclic lipopeptide antimicrobial, is bactericidal against a range of gram-positive bacteria, including many multiple-drug-resistant isolates. It has only minimal activity against anaerobic bacteria and no activity against gram-negative bacteria. Daptomycin exhibits linear pharmacokinetics, and the plasma concentration-versus-time relationship is best described by a two-compartment model with first-order elimination. The initial bactericidal activity is rapid, extensive, and concentration related. In clinical trials, daptomycin has shown efficacy in treating complicated skin and skin-structure infections (CSSSIs); the drug carries FDA-approved labeling for same. The adverse effects of daptomycin appear comparable to those of vancomycin and semisynthetic penicillins. The dosage for CSSSIs is 4 mg/kg by i.v. infusion every 24 hours.

CONCLUSION

Daptomycin is bactericidal against gram-positive organisms and offers an option in the treatment of CSSSIs.

Penetration of ciprofloxacin and its desethylenemetabolite into skin in humans after a single oral dose of the parent drug assessed by cutaneous microdialysis

OBJECTIVE

To measure the concentration of ciprofloxacin and its desethylenemetabolite in plasma and cutaneous microdialysates and to compare ciprofloxacin penetration into cutaneous microdialysates against theoretically predicted penetration in a peripheral compartment.

METHOD

A single oral dose of 0.5 g of the parent drug was administered to 10 healthy male volunteers. Microdialysis probes with 2 kDa molecular weight cut-off were inserted intradermally and were perfused with Ringer solution up to 8 h after drug ingestion. Drug and metabolite concentrations were measured by high performance liquid chromatography.

RESULTS

Mean maximum concentrations of ciprofloxacin in plasma, cutaneous microdialysates and theoretical peripheral compartment were 7.01+/-1.69, 2.95+/-0.64 and 3.37+/-0.60 micromol/L, respectively, and were achieved after about 2.0+/-0.6, 2.4+/-0.9 and 4.8+/-0.9 h. The extent of penetration into cutaneous microdialysates and theoretical peripheral compartment relative to plasma were 0.550+/-0.150 and 0.788+/-0.131, respectively, and differed significantly. Similarly, time to maximum concentration as well as area under the concentration-time curve in these compartments also differed significantly unlike the maximum concentration.

CONCLUSION

Microdialysis permits the evaluation of the penetration of drug and its metabolites into target tissues. Such evaluation is helpful to optimize treatment strategies. After a single 0.5 g oral dose, ciprofloxacin penetrated into skin and achieved concentrations above the minimum inhibitory concentrations for susceptible pathogens, recommended by the National Committee for Clinical Laboratory Standards (NCCLS).

Daptomycin: a cyclic lipopeptide antimicrobial agent

Objectives:

The aims of this article were: to summarize the pharmacology, pharmacokinetics, and efficacy ofdaptomycin; to explore its safety profile; and to discuss its current and potential roles as an antimicrobial therapy.

Methods:

A literature search was conducted using the MEDLINE (1966–August 2004) and InternationalPharmaceutical Abstracts (1970–August 2004) databases with the search terms daptomycin, LY146032, and lipopeptide antibiotics. Abstracts of the Interscience Conference on Antimicrobial Agents and Chemotherapy and documents submitted to the US Food and Drug Administration were also reviewed.

Results:

Phase III study results suggest no difference in efficacy or tolerability between daptomycin 4 mg/kgIV QD and vancomycin or semisynthetic penicillins for complicated skin and skin-structure infections. Animal studies suggest daptomycin may be useful for the treatment of endocarditis. Daptomycin is not indicated for pneumonia, with poorer outcomes than conventional treatment It is available as an IV medication and exhibits 92% plasma protein binding in vitro. In healthy adult humans, daptomycin has a volume of distribution of 0.1 Ukg and a plasma elimination half-life of ∼9 hours, and is eliminated primarily by renal excretion (∼54%). In patients with reduced renal function, including those receiving hemodialysis and peritoneal dialysis, the dose interval should be 48 hours. No dosage adjustment appears to be necessary for mild to moderate hepatic impairment. The use of daptomycin in patients with severe hepatic impairment has not been assessed. The most commonly reported adverse events include constipation, nausea, injection-site reactions, headache, and diarrhea. Patients should also be monitored regularly for skeletal muscle toxicity.

Conclusions:

Daptomycin may be useful for complicated skin and skin-structure infections and gram-positive pathogens resistant to conventional antimicrobials. However, limited data are currently available for duration of treatment beyond 14 days and at doses >4 mg/kg QD.

Daptomycin: a lipopeptide antibiotic for the treatment of serious Gram-positive infections

Infections caused by drug-resistant pathogens are on the rise. Daptomycin, a cyclic lipopeptide with activity against most Gram-positive pathogens, including vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus, is a newly US-FDA approved antimicrobial for complicated skin and skin structure infections (cSSSI). Daptomycin has a unique mechanism of action that results in destruction of the membrane potential. The rapid bactericidal activity of daptomycin makes it an attractive antibiotic for serious Gram-positive infections.

Daptomycin – a novel antibiotic against Gram-positive pathogens

Daptomycin is a novel member of a new class of antimicrobial agents used in treating resistant Gram-positive infections. These infections are becoming more commonplace and treatment options are limited. At present, daptomycin is approved for use in the US for complicated skin and skin-structure infections that are a common complication of surgery, diabetic foot ulcers, and burns. The most common causative organisms in these types of infections are Staphylococcus aureus, Streptococcus pyogenes, Streptococcus agalactiae, and Group C and G streptococci. Traditionally, these infections have been treated with penicillin and cephalosporins, but resistance to these agents is widespread and increasing. Of particular concern is the rapid increase in methicillin-resistant S. aureus (MRSA). The SENTRY Antimicrobial Surveillance Programme reported that approximately 30% of S. aureus isolates from skin and skin-structure infections were MRSA. The standard treatment for MRSA infections is vancomycin but resistance to this agent is also developing. There is a continuing need for the development of new antibiotics with Gram-positive activity, to combat multi-drug-resistant Gram-positive infections.

Pharmacodynamics of cefepime alone and in combination with various antimicrobials against methicillin-resistant Staphylococcus aureus in an in vitro pharmacodynamic infection model

Treatment options for gram-positive resistant bacteria are limited; therefore, efforts to evaluate therapy options in the critical care population are warranted. Cefepime has broad-spectrum activity against gram-negative and gram-positive organisms. We have previously demonstrated that the combination of cefepime with vancomycin, linezolid, or quinupristin-dalfopristin had an improved or enhanced effect against methicillin-resistant Staphylococcus aureus (MRSA). We investigated various regimens of cefepime alone and in combination against two clinical MRSA isolates (R2481 and R2484) in an established in vitro pharmacodynamic model. Human pharmacokinetic regimen simulations were as follows: cefepime, 2 g every 8 h (q8h) (C8) and 12 h (C12), continuous-infusion 2-g loading dose followed by 4 g alone or in combination with gentamicin and tobramycin (1.0 or 2.0 [G1 and G2 or TB1 and TB2] mg/kg of body weight q12h and 5.0 [G5 or TB5] mg/kg q24h), arbekacin (ARB) (100 mg q12h), linezolid (LIN) (600 mg q12h), tigecycline (TIG) (100 mg q24h), or daptomycin (DAP) (6 mg/kg q24h) for 48 h. The MICs for cefepime, gentamicin, tobramycin, ARB, LIN, TIG, and DAP for the two clinical MRSA isolates (R2481 and R2484) were 4 and 4, 0.25 and 0.5, 128 and 0.5, 0.5 and 0.125, 2 and 4, 0.25 and 0.25, and 0.0625 and 0.125 microg/ml, respectively. At 48 h, combinations of C12 and C8 plus ARB, G1, or G5 (range, -2.05- to -4.32-log(10) decrease) demonstrated enhanced lethality against R2481 (resistant to tobramycin) (P < 0.05). A similar relationship was demonstrated against R2484 with cefepime plus ARB, gentamicin, or tobramycin (range, -2.05- to -3.63-log(10) decrease) (P < 0.05). A 99.9% kill was achieved with cefepime plus aminoglycoside combinations as early as 2 h and maintained throughout the 48-h period. TIG was antagonistic when combined with C12 against both isolates. DAP alone achieved 99.9% kill for up to 48 h for both isolates and was the most active agent against R2481 and R2484 (-2.89- and -3.61-log(10) decrease at 48 h); therefore, combination therapy did not enhance lethality. Overall, the most potent combinations noted were cefepime in combination with low- and high-dose aminoglycosides. Further investigations with combination therapies are warranted.

Daptomycin is highly efficacious against penicillin-resistant and penicillin- and quinolone-resistant pneumococci in experimental meningitis

The penetration of daptomycin, a new lipopeptide antibiotic, into inflamed meninges ranged between 4.37 and 7.53% (mean, 5.97%). Daptomycin was very efficacious in the treatment of experimental pneumococcal meningitis, producing a decrease of -1.20 +/- 0.32 Deltalog(10) CFU/ml. h in the bacterial titer of Streptococcus pneumoniae against a penicillin-resistant strain and of -0.97 +/- 0.32 Deltalog(10) CFU/ml. h against a penicillin- and quinolone-resistant strain found in cerebrospinal fluid (CSF). For both strains, daptomycin was significantly superior to the standard regimen of a combination of ceftriaxone with vancomycin, sterilizing 9 of 10 CSF samples after 4 h. In vitro, daptomycin produced highly bactericidal activity in concentrations above the MIC.

Methicillin-resistant Staphylococcus aureus infections in ICU patients

The incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections in patients admitted to the intensive care unit has dramatically increased in recent years, with an associated increase in morbidity and mortality and the costs of caring for patients with MRSA infections. Although indiscriminate and inappropriate use of antibiotics has contributed to this phenomenon, horizontal transmission of MRSA between patients and health care providers is the principal cause of this observed increase. This article discusses the pathogenesis, epidemiology, treatment, and prevention of MRSA infections in critically ill patients.

Clinical glycopeptide-intermediate staphylococci tested against arbekacin, daptomycin, and tigecycline

We examined the activity of arbekacin, daptomycin, tigecycline, and vancomycin against various Staphylococci isolates with glycopeptide-intermediate (n = 25) and heterogeneous susceptibilities (n = 22) (GISS and hGISS). The minimum inhibitory concentrations (MIC) of each antimicrobial was evaluated in time-kill experiments by using 4 randomly selected GISS isolates tested at 2 and 4 times their respective MIC. The MIC(90) microg/mL ranges for arbekacin, daptomycin, tigecycline, and vancomycin were 2 (0.25-4), 1 (0.0625-2), 0.5 (0.0625-2), and 8 (4-8), respectively. Time kill at 2 times the MIC demonstrated a mean log(10) colony forming units (CFU)/mL change of -2.98 +/- 0.708, -3.6 +/- 0.509, -2.48 +/- 0.647, and +1.14 +/- 0.1 arbekacin, daptomycin, tigecycline, and vancomycin, respectively. At 4 times the MIC, significant activity for all compounds was noted with a log(10) CFU/mL decrease range from 3.68 to 2.74 +/- 0.66. Overall, all the antimicrobials tested (with the exception of vancomycin) exhibited significant in vitro activity against GISS. These compounds may offer therapeutic options for the treatment of GISS.

Population pharmacokinetics of daptomycin

Data from subjects in nine phase 1 (n = 153) and six phase 2/3 (n = 129) clinical trials were combined to identify factors contributing to interindividual variability in daptomycin pharmacokinetics (PK). Over 30 covariates were considered. A two-compartment model with first-order elimination provided the best fit for data on daptomycin concentrations in plasma over time. In the final population PK model, daptomycin plasma clearance (CL) was a function of renal function, body temperature, and sex. Of these factors, renal function contributed most significantly to interindividual variability. CL varied linearly with the estimated creatinine clearance. CL among dialysis subjects was approximately one-third that of healthy subjects (0.27 versus 0.81 liter/h). CL in females was 80% that in males; however, in clinical trials, the outcome was not affected by sex and therefore this effect is not considered clinically meaningful. The relationship with body temperature should be interpreted cautiously since the analysis included only a limited number of subjects who were hyperthermic. The volume of distribution of the peripheral compartment (V2) and intercompartmental clearance (Q) were linearly related to body weight. V2 increased approximately twofold in the presence of an acute infection. No factors were identified that significantly impacted V1. This analysis supports the dosing of daptomycin on a milligram-per-kilogram-of-body-weight basis and suggests that modified dosing regimens are indicated for patients with severe renal disease and for those undergoing dialysis.

Single-dose pharmacokinetics of daptomycin in young and geriatric volunteers

Daptomycin is a novel lipoprotein antibiotic that was recently approved for the treatment of complicated skin and skin structure infections caused by aerobic gram-positive bacteria. The pharmacokinetics of daptomycin was evaluated after a single 0.5-hour intravenous infusion of 4 mg/kg to groups of young adult (18-30 years) and geriatric (>or= 75 years) volunteers. Daptomycin was safe and well tolerated. No adverse events related to the infusion were reported. With increased age, there were increases in the area under the plasma concentration-time curve extrapolated to infinity (AUC( infinity )) and the terminal elimination half-life. Systemic (CL) and renal clearance (CL(R)) both decreased with increasing age. The observed changes seen in CL between the two cohorts were most likely a result of changes in renal function, as estimated by creatinine clearance. No statistically significant differences were observed between the two groups in the maximum plasma concentration (C(max)) and volume of distribution at steady state (Vd(ss)). The confidence intervals for the arithmetic mean ratios of the fraction of the dose excreted in the urine as daptomycin (%Fe) (geriatric subjects over younger subjects) were 60% to 101%, indicating that %Fe(dose) was lower in geriatric subjects. These results demonstrate that changes in the pharmacokinetics of daptomycin in the elderly are attributable to changes in renal function, whereas age per se is not a significant factor.

Application of cutaneous microdialysis to evaluate metronidazole and its main metabolite concentrations in the skin after a single oral dose

OBJECTIVE

To measure the concentration of metronidazole and its hydroxymetabolite in plasma and cutaneous microdialysates and to compare metronidazole penetration into cutaneous microdialysates against theoretical predicted penetration in a peripheral compartment.

METHOD

A single oral dose of 2 g of the parent drug was administered to 10 healthy male volunteers. Microdialysis probes with 2 kDa molecular weight cut-off were inserted intradermally and were perfused with Ringer solution up to 8 h after drug ingestion. Drug and metabolite concentrations were measured by high performance liquid chromatography.

RESULTS

Mean maximum concentration in plasma, cutaneous microdialysates and theoretical peripheral compartment were 214 +/- 49, 151 +/- 52 and 146 +/- 38 micromol/L, respectively, and were achieved after about 2.1 +/- 0.8, 2.8 +/- 1.0 and 6.0 +/- 2.9 h. The extent of penetration into cutaneous microdialysates and theoretical peripheral compartment relative to plasma were 0.672 +/- 0.196 and 0.675 +/-0.207, respectively, and did not differ significantly. Moreover, maximum concentration as well as area under concentration-time curve in these compartments also did not differ significantly.

CONCLUSION

Use of cutaneous microdialysis technique permits the characterization of true systemic drug disposition, for optimizing drug treatment strategies.

Daptomycin

Daptomycin is a lipopeptide antibacterial with rapid in vitro activity against Gram-positive cocci. It is approved for use in patients with complicated skin and skin structure infections (cSSSIs) caused by specified Gram-positive cocci. In vitro, daptomycin was active against Staphylococcus aureus (including meticillin-resistant strains), Streptococcus pyogenes, S. agalactiae, group C and G beta-haemolytic streptococci and vancomycin-susceptible Enterococcus faecalis. Bactericidal activity in vitro was rapid and concentration dependent. In two randomised, investigator-blinded, multicentre trials in patients with cSSSIs, intravenous daptomycin 4 mg/kg once daily was as effective as standard therapy (intravenous semi-synthetic penicillin 4-12 g/day or vancomycin 1 g 12-hourly). Clinical success rates assessed 6-20 days after treatment end were 82.1% in daptomycin recipients and 82.9% in recipients of standard therapy (pooled data). In patients with cSSSIs, the adverse event profiles of daptomycin and vancomycin were similar. Creatine phosphokinase (CPK) levels increased in 2.8% of daptomycin recipients and 1.8% of patients who received standard therapy; only one daptomycin recipient (0.2%) experienced increased CPK levels and muscle symptoms that were not associated with any comorbid factors.

Daptomycin

Daptomycin, the first in a class of agents known as lipopeptides, is a novel antimicrobial agent used for the treatment of gram-positive infections. The compound has a distinctive mechanism of action that exerts its bactericidal activity by disrupting plasma membrane function without penetrating into the cytoplasm. The agent has received much interest because of its activity against multidrug-resistant, gram-positive bacteria such as methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, and glycopeptide-intermediate and -resistant S. aureus. Daptomycin demonstrates concentration-dependent killing and is eliminated primarily by glomerular filtration. It was approved in September 2003 for the treatment of complicated skin and soft tissue infections. It has a safety profile similar to other agents commonly administered to treat gram-positive infections. Daptomycin is a welcome addition to the antimicrobial armamentarium for the treatment of bacterial infections. Further clinical experience with this compound will help define its role in the treatment of resistant gram-positive organisms.

Novelties in the field of antimicrobial compounds for the treatment of lower respiratory tract infections

Emergence of antimicrobial resistance is a growing problem and a public health threat. New drugs must be designed with emerging needs in mind: specific resistant and hard-to-treat organisms. But the difficulty to find real new drugs is a major problem. Only the oxazolidinones, the cationic peptides and the lipopeptide antibiotics can be truly regarded as structurally novel drugs, although the peptide deformylase inhibitors and, possibly, the pleuromutilins can be considered a potential advancement in the field. Obviously, these antibiotics must be reserved only to cases of documented ineffectiveness of the common antimicrobial agents.

Postantibiotic effects of daptomycin against 14 staphylococcal and pneumococcal clinical isolates

Daptomycin mean staphylococcal postantibiotic effects (PAEs) were 1.1 to 6.2 h, with a mean of 2.5 h. The mean pneumococcal PAEs were 1.7 h, ranging between 1.0 and 2.5 h. The staphylococcal and pneumococcal postantibiotic sub-MIC effects at 0.4 times the MIC ranged from 3.0 to >12.0 h and 1.9 to >12.0 h, respectively.