Loracarbef, after oral administration, was approximately 90% absorbed from the gastrointestinal tract. When capsules were taken with food, peak plasma concentrations were 50% to 60% of those achieved when the drug was administered to fasting subjects and occurred from 30 to 60 minutes later. Total absorption, as measured by urinary recovery and area under the plasma concentration versus time curve (AUC), was unchanged. The effect of food on the rate and extent of absorption of the suspension formulation has not been studied to date.

The pharmacokinetics of loracarbef were linear over the recommended dosage range of 200 to 400 mg, with no accumulation of the drug noted when it was given twice daily.

Average peak plasma concentrations after administration of 200-mg or 400-mg single doses of loracarbef as capsules to fasting subjects were approximately 8 to 14 mcg/ml, respectively, and were obtained within 1.2 hours after dosing. The average peak plasma concentration in adults following a 400-mg single dose of suspension was 17 mcg/ml and was obtained within 0.8 hour after dosing (see TABLE 1).

TABLE 1
	Mean Plasma Loracarbef Concentrations (mcg/ml)
Dosage (mg)	Peak Cmax	Time to Peak Tmax
Capsule (single dose)
200 mg	8	1.2 h
400 mg	14	1.2 h
Suspension (single dose)
400 mg (adult)	17	0.8 h
7.5 mg/kg (pediatric)	13	0.8 h
15 mg/kg (pediatric)	19	0.8 h

Following administration of 7.5 and 15 mg/kg single doses of oral suspension to children, average peak plasma concentrations were 13 and 19 mcg/ml, respectively, and were obtained within 40 to 60 minutes.

This increased rate of absorption (suspension > capsule) should be taken into consideration if the oral suspension is to be substituted for the capsule, and capsules should not be substituted for the oral suspension in the treatment of otitis media (see DOSAGE AND ADMINISTRATION).

The elimination half-life was an average of 1.0 h in patients with normal renal function. Concomitant administration of probenecid decreased the rate of urinary excretion and increased the half-life to 1.5 hours.

In subjects with moderate impairment of renal function (creatinine clearance 10 to 50 ml/min/1.73 m²), following a single 400-mg dose, the plasma half-life was prolonged to approximately 5.6 hours. In subjects with severe renal impairment (creatinine clearance <10 ml/min/1.73 m²), the half-life was increased to approximately 32 hours. During hemodialysis the half-life was approximately 4 hours. In patients with severe renal impairment, the C_max increased from 15.4 mcg/ml to 23 mcg/ml (see PRECAUTIONS and DOSAGE AND ADMINISTRATION).

In single-dose studies, plasma half-life and AUC were not significantly altered in healthy elderly subjects with normal renal function.

There is no evidence of metabolism of loracarbef in humans.

Approximately 25% of circulating loracarbef is bound to plasma proteins.

Middle-ear fluid concentrations of loracarbef were approximately 48% of the plasma concentration 2 hours after drug administration in pediatric patients. The peak concentration of loracarbef in blister fluid was approximately half that obtained in plasma. Adequate data on CSF levels of loracarbef are not available.

Microbiology: Loracarbef exerts its bactericidal action by binding to essential target proteins of the bacterial cell wall, leading to inhibition of cell-wall synthesis. It is stable in the presence of some bacterial b-lactamases. Loracarbef has been shown to be active against most strains of the following organisms both in vitro and in clinical infections (see INDICATIONS AND USAGE).

Gram-positive aerobes:

Staphylococcus aureus(including penicillinase-producing strains)

NOTE: Loracarbef (like most b-lactam antimicrobials) is inactive against methicillin-resistant staphylococci.

Staphylococcus saprophyticus
Streptococcus pneumoniae
Streptococcus pyogenes

Gram-negative aerobes:

Escherichia coli
Haemophilus influenzae (including b-lactamase-producing strains)
Moraxella (Branhamella) catarrhalis (including b-lactamase-producing strains)

The following in vitro data are available; however, their clinical significance is unknown.

Loracarbef exhibits in vitro minimum inhibitory concentrations (MIC) of 8 mcg/ml or less against most strains of the following organisms; however, the safety and efficacy of loracarbef in treating clinical infections due to these organisms have not been established in adequate and well-controlled trials.

Gram-positive aerobes:

Staphylococcus epidermidis
Streptococcus agalactiae (group B streptococci)
Streptococcus bovis
Streptococci groups C, F, and Gy
viridans group streptococci

Gram-negative aerobes:

Citrobacter diversus
Haemophilus parainfluenzae
Klebsiella pneumoniae
Neisseria gonorrhoeae (including penicillinase-producing strains)
Pasteurella multocida
Proteus mirabilis
Salmonella species
Shigella species
Yersinia enterocolitica

NOTE: Loracarbef is inactive against most strains of Acinetobacter, Enterobacter, Morganella morganii, Proteus vulgaris, Providencia, Pseudomonas, and Serratia.

Anaerobic organisms:

Clostridium perfringens
Fusobacterium necrophorum
Peptococcus niger
Peptostreptococcus intermedius
Propionibacterium acnes

Susceptibility Testing

Diffusion Techniques: Quantitative methods that require measurement of zone diameters give the most precise estimate of the susceptibility of bacteria to antimicrobial agents. One such standardized method¹ has been recommended for use with the 30-mcg loracarbef disk. Interpretation involves the correlation of the diameter obtained in the disk test with MIC for loracarbef.

Reports from the laboratory giving results of the standard single-disk susceptibility test with a 30 mcg loracarbef disk should be interpreted according to the following criteria (TABLE 2).

TABLE 2
Zone diameter (mm)	Interpretation
³ 18	(S) Susceptible
15-17	(MS) Moderately Susceptible
£ 14	(R) Resistant

A report of "susceptible" implies that the pathogen is likely to be inhibited by generally achievable blood concentrations. A report of "moderately susceptible" indicates that inhibitory concentrations of the antibiotic may be achieved if high dosage is used or if the infection is confined to tissues and fluids (e.g., urine) in which high antibiotic concentrations are attained. A report of "resistant" indicates that achievable concentrations of the antibiotic are unlikely to be inhibitory and other therapy should be selected.

Standardized procedures require the use of laboratory control organisms. The 30-mcg loracarbef disk should give the following zone diameters with the NCCLS approved procedure (TABLE 3).

TABLE 3
Organism	Zone Diameter (mm)
E. coli ATCC 25922	23-29
S. aureus ATCC 25923	23-31

Dilution Techniques: Use a standardized dilution method² (broth, agar, or microdilution) or equivalent with loracarbef powder. The MIC values obtained should be interpreted according to the following criteria (TABLE 4).

TABLE 4
MIC (mcg/ml)	Interpretation
£8	(S) Susceptible
16	(MS) Moderately Susceptible
³32	(R) Resistant

As with standard diffusion methods, dilution procedures require the use of laboratory control organisms. Standard loracarbef powder should give the following MIC values with the NCCLS approved procedure (TABLE 5):

TABLE 5
Organism	MIC Range (mcg/ml)
E. coli ATCC 25922	0.5-2
S. aureus ATCC 29213	0.5-2

CLINICAL STUDIES

Acute Otitis Media

Study 1: In a controlled clinical study of acute otitis media performed in the United States where significant rates of b-lactamase-producing organisms were found, loracarbef was compared to an oral antimicrobial agent that contained a specific b-lactamase inhibitor. In this study, using very strict evaluability criteria and microbiologic and clinical response criteria at the 10- to 16-day post therapy follow-up, the following presumptive bacterial eradication/clinical cure outcomes (i.e., clinical success) and safety results were obtained (see TABLE 6).

TABLE 6 U.S. Acute Otitis Media Study Loracarbef vs b-lactamase inhibitor-containing control drug
Efficacy
Pathogen	% of Cases With Pathogens (n=204)	Outcome
S. pneumoniae	42.6%	Loracarbef equivalent to control
H. influenzae	30.4%	Loracarbef success rate 9% less than control
M. catarrhalis	20.6%	Loracarbef success rate 19% less than control
S. pyogenes	6.4%	Loracarbef equivalent to control
Overall	100.0%	Loracarbef success rate 12% less than control

Safety: The incidences of the following adverse events were clinically and statistically significantly higher in the control arm versus the loracarbef arm (TABLE 7).

TABLE 7
Event	Loracarbef	Control
Diarrhea	15%	26%
Rash*	8%	15%
* The majority of these involved the diaper area in young pediatric patients.

Study 2: In a controlled clinical study of acute otitis media performed in Europe, loracarbef was compared to amoxicillin. As expected in a European population, this study population had a lower incidence of b- lactamase-producing organisms than usually seen in U.S. trials. In this study, using very strict evaluability criteria and microbiologic and clinical response criteria at the 10- to 16-day post therapy follow-up, the following presumptive bacterial eradication/clinical cure outcomes (i.e., clinical success) were obtained (see TABLE 8).

TABLE 8 European Acute Otitis Media Study: Loracarbef vs Amoxicillin
Efficacy
Pathogen	% of Cases With Pathogens (n=291)	Outcome
S. pneumoniae	51.5%	Loracarbef equivalent to amoxicillin
H. influenzae	29.2%	Loracarbef success rate 14% greater than amoxicillin
M. catarrhalis	15.8%	Loracarbef success rate 31% greater than amoxicillin
S. pyogenes	3.4%	Loracarbef equivalent to amoxicillin
Overall	100.0%	Loracarbef equivalent to amoxicillin

Acute Maxillary Sinusitis

In a controlled clinical study of acute maxillary sinusitis performed in Europe, loracarbef was compared to doxycycline. In this study there were 210 sinus-puncture evaluable patients. As expected in a European population, this study population had a lower incidence of b-lactamase-producing organisms than usually seen in U.S. trials. In this study, using very strict evaluability criteria and microbiologic and clinical response criteria at the 1- to 2-week post therapy follow-up, the following presumptive bacterial eradication/clinical cure outcomes (i.e., clinical success) were obtained (see TABLE 9).

TABLE 9 European Acute Maxillary Sinusitis Study: Loracarbef vs Doxycycline
Efficacy
Pathogen	% of Cases With Pathogens (n=210)	Outcome
S. pneumoniae	47.6%	Loracarbef equivalent to doxycycline
H. influenzae	41.4%	Loracarbef equivalent to doxycycline
M. catarrhalis	11.0%	Loracarbef equivalent to doxycycline
Overall	100.0%	Loracarbef equivalent to doxycycline

Cystitis

Study 1: In a controlled clinical study of cystitis performed in the United States, loracarbef was compared to cefaclor. In this study, using very strict evaluability criteria and microbiologic and clinical response criteria at the 5- to 9-day post therapy follow-up, the following bacterial eradication rates were obtained (see TABLE 10 ).

TABLE 10 U.S. Uncomplicated Cystitis Study: Loracarbef vs Cefaclor
Efficacy
Pathogen	% of Cases With Pathogens (n=186)	Outcome
E. coli	77.4%	Loracarbef eradication rate 4% greater than cefaclor (loracarbef eradication rate 80%)
Other major  Enterobacteriaceae	12.5%	Loracarbef equivalent to cefaclor (loracarbef eradication rate 61%)
S. saprophyticus	3.8%	Loracarbef equivalent to cefaclor

Study 2: In a second controlled clinical study of cystitis, performed in Europe, loracarbef was compared to an oral quinolone. In this study, using very strict evaluability criteria and microbiologic and clinical response criteria at the 5- to 9-day post therapy follow-up, the following bacterial eradication rates were obtained (see TABLE 11).

TABLE 11 European Uncomplicated Cystitis Study: Loracarbef vs Quinolone
Efficacy
Pathogen	% of Cases With Pathogens (n=189)	Outcome
E. coli	82.0%	Loracarbef eradication rate 7% less than quinolone (loracarbef eradication rate 81%)
Other major  Enterobacteriaceae	10.1%	Loracarbef eradication rate 32% less than quinolone (loracarbef eradication rate 50%)

Last reviewed on RxList: 12/8/2004
This monograph has been modified to include the generic and brand name in many instances.