pH and P.E.G.-400 effects on flucloxacillin absorption

1. Intestinal clearances of flucloxacillin significantly decrease with the increase of pH, concomitantly with a decrease of the percent absorbed at 60 min. 2. The apparent rate constants for unionized (Ku) and ionized species are 0.173 min-1 and 0.017 min-1 respectively. 3. The addition of P.E.G.-400 at different concentrations significantly enhanced intestinal clearances of flucloxacillin parallel to an increase of net water flux from the lumen of the small intestine.

The penetration of antibiotics into the normal intervertebral disc

The role of antibiotics in the treatment of disc-space infection is controversial. This study assessed the tissue penetration of flucloxacillin and cephradine into the normal intervertebral disc after intravenous administration of a bolus dose of antibiotic. Twenty-five discs were removed from 12 adolescent patients having anterior spinal surgery to correct scoliosis; antibiotic had been administered between 30 minutes and four hours before operation. Despite high blood levels, no antibiotic could be detected by bioassay or by high-pressure liquid chromatography (h.p.l.c.) in any of the specimens from the nucleus pulposus or the annulus fibrosus.

A controlled trial of nebulized aminoglycoside and oral flucloxacillin versus placebo in the outpatient management of children with cystic fibrosis

Six children with cystic fibrosis who had persistently had Pseudomonas aeruginosa isolated from their respiratory tract, completed a double-blind cross-over comparison of oral flucloxacillin and nebulized aminoglycoside versus double placebo. The patients had higher FEV1 results at the end of the month of active treatment than after the month of placebo.

Antibiotic levels in bovine lacrimal fluid after single application of ointments containing procaine benzyl penicillin plus dihydrostreptomycin; and benzathine cloxacillin

The efficacy of an experimental slow-release formulation, containing procaine benzyl penicillin and dihydrostreptomycin, was investigated in a cross-over study with a cloxacillin eye ointment in 12 cows with clinically normal eyes. After a single topical application the therapeutic concentrations of penicillin were sustained for 48 to 92 hours and of cloxacillin for 32 to 48 hours. These long-acting ointments will simplify the successful treatment of painful eye disorders such as keratoconjunctivitis. A practical and non-irritant method for sampling tears is described.

Flucloxacillin in chronic leg ulcers. Penetration of flucloxacillin into chronic leg ulcer exudate and the effect on the bacteria

The penetration of flucloxacillin into ulcer exudate was investigated in six patients with chronic leg ulcers. The flucloxacillin dosage used was 1 g orally three times daily for three days, and the serum and exudate concentrations were measured repeatedly during a 10 h-period following the first and the seventh dose. All the ulcers were contaminated with (S. aureus) Staphylococcus aureus either in pure culture (three ulcers) or in culture mixed with Gram-negative bacteria (three ulcers). Bacterial counting in the ulcers was performed twice before and twice during the antibiotic treatment. The flucloxacillin concentrations measured in the ulcer exudate were found to be lower than the corresponding serum concentrations. However, the exudate concentrations were found to be above the minimum inhibitory concentration (MIC) for the contaminating S. aureus during an average of 7 h after each dose, and the number of S. aureus during the treatment period was reduced to less than 0.01% of the initial number. The Gram-negative bacteria were not susceptible to flucloxacillin. The number of these bacteria decreased before flucloxacillin treatment but increased again during treatment, probably owing to the changed conditions in the ulcers following the marked decrease in the number of S. aureus.

The influence of flucloxacillin and amoxicillin with clavulanic acid on the aerobic flora of the alimentary tract

In a randomized study, 42 patients undergoing extensive maxillo-facial surgery (correction of the position of the mandible or maxilla by using autologous bone transplants) received prophylactically ten-day courses of either flucloxacillin or amoxicillin with clavulanic acid. Patients were comparable with regard to age and type of surgery. During the prophylactic treatment the effect of antibiotics used on the microbial flora of the alimentary tract was studied. Patients receiving flucloxacillin showed increased numbers of Klebsiella spp. isolated from the faeces (59% of the patients versus 19% of the patients receiving amoxicillin with clavulanic acid). Patients receiving amoxicillin with clavulanic acid showed higher colonization rates of oropharynx with Enterobacteriaceae than patients receiving flucloxacillin (ten patients versus five patients). 60% of those strains isolated from patients receiving amoxicillin with clavulanic acid were resistant to this combination, as compared to 20% of gram-negative bacilli isolated from patients receiving flucloxacillin. In 50% of patients receiving amoxicillin with clavulanic acid, colonization of the gut with yeast occurred, as compared to 18% of patients receiving flucloxacillin. Only one infection leading to a partial loss of the graft was seen in the group of patients receiving flucloxacillin.

Floxacillin-induced cholestatic hepatitis with evidence of lymphocyte sensitization

A severe and prolonged form of biopsy-proved cholestatic hepatitis occurred in a 45-year-old man who had received floxacillin for two weeks preceding the episode of drug-related cholestatic injury. Immunologic tests revealed evidence of in vitro sensitization to the drug as well as to the serum of a normal subject collected after ingestion of floxacillin. Floxacillin should be added to the list of drugs causing cholestatic hepatitis, most likely by an immunologic mechanism.

Plasma concentration following oral administration of di- and flucloxacillin in infants and children

The bioavailability of commercial liquid preparations of di- and flucloxacillin was compared in infants and children. The plasma concentrations following a dose of 12.5 mg/kg were equal within the two age groups. Infants 0-1 months old, however, demonstrated a better absorption than older children.

Early termination of a prospective, randomized trial comparing teicoplanin and flucloxacillin for treating severe staphylococcal infections

In a prospective, randomized trial, teicoplanin (at a 400-mg intravenous loading dose followed by 200 mg/day intravenously or intramuscularly) was compared with flucloxacillin (8 g/day) in patients with severe staphylococcal infections. Teicoplanin proved unsatisfactory for the following reasons: failures or relapses were more frequent in the teicoplanin group, and blood levels were difficult to predict and tended to be low 24 hr after the loading dose. Future trials with this agent should use much-higher doses.

Pharmacokinetics of free and total flucloxacillin in newborn infants

Flucloxacillin 50 mg/kg b.w. was administered intravenously (in combination with ampicillin/gentamicin) and orally (with amoxicillin) to 9 newborn infants (gestational age 33-41 weeks) to treat bacterial infections. The concentrations of flucloxacillin in plasma and urine after i.v. injection were analysed according to an open two-compartment model, and the plasma protein binding of flucloxacillin and its distribution to blood cells and plasma water in whole blood were determined. Considerable differences were found from values reported in adults. The terminal half-life averaged 4 h 38 min and was significantly correlated with gestational age. Plasma clearance was low (0.744 ml X min-1 X kg-1), due to the small renal clearance (0.182 ml X min-1 X kg-1), whilst non-renal clearance (0.563 ml X min-1 X kg-1) was approximately the same as in adults. The mean apparent volume of distribution of total drug (Vz) was 0.280 l/kg. The corresponding volume of distribution of unbound drug (Vu1 + Vu2) was 1.74 l/kg, which indicates considerable extravascular drug binding. The plasma protein binding of flucloxacillin (mean 86.3%) was significantly correlated with gestational age and the bilirubin/albumin concentration ratio. Bioavailability after oral administration, when corrected for changes in terminal half-life, was 47.7%, which is only slightly lower than that reported in adults. Since the plasma concentrations after both i.v. and oral administration were well above the MIC-values generally reported for Staphylococcus aureus, and since few side-effects were observed, intravenous injection or, in selected cases, orl administration of flucloxacillin appears to be a reliable therapy for the treatment of infections due to sensitive strains of S. aureus in premature newborn infants.

Delayed inactivation of Citrobacter freundii cephalosporinase by 6 beta-[3-(2-chlorophenyl)-5-methyl-4-isoxazolyl]penicillin sulfone

When Citrobacter freundii cephalosporinase was incubated with 6 beta-[3-(2-chlorophenyl)-5-methyl-4-isoxazolyl]penicillin sulfone (cloxacillin sulfone) in phosphate buffer, the enzyme was suddenly inactivated just after the completion of enzymatic degradation of the cloxacillin sulfone. Such delayed inactivation was due to a secondary inhibitor formed from cloxacillin sulfone during the incubation period. The inactivation was delayed due to the protection of the enzyme by cloxacillin sulfone from the attack of the secondary inhibitor. Phosphate anions were essential for the formation of the secondary inhibitor. However, once the secondary inhibitor was formed, the inactivation occurred in the absence of phosphate anions although the degree of the inactivation depended on the length of the preincubation period with phosphate anions. The main species (more than 80%) of the inactivated enzyme was detected as a single protein band with a slightly lower pI value than that of the native enzyme on isoelectric focusing on a plate.

Extravascular penetration of highly protein-bound flucloxacillin

The pharmacokinetics of intravenously administered flucloxacillin (2.0 g to five volunteers) are described. The passage of flucloxacillin to peripheral lymph and suction skin blisters was monitored. This drug was selected because the high serum protein binding of 96% offered a particularly good opportunity for the study of the impact on tissue penetration. Flucloxacillin was assayed by high-pressure liquid chromatography, and pharmacokinetics were assayed by computerized curve fitting to accepted models. Penetration of flucloxacillin to extravascular foci was rapid. After 30 min the drug concentrations were 0.5 +/- 0.3 microgram/ml in lymph and 0.9 +/- 0.7 microgram/ml in blister fluid. The peak concentration was 11.7 +/- 5.6 micrograms/ml in lymph and 4.6 +/- 1.4 micrograms/ml in blister fluid. Concentrations in urine were above 111 +/- 50 micrograms/ml throughout the 8-h monitoring period, and urinary recovery was 60.4%. The half-life was 2.1 +/- 0.9 h in serum, 1.4 +/- 0.6 h in lymph, and 11.0 +/- 4.1 h in blister fluid. The differences in half-life were significant (P less than 0.05) between serum and blister fluid but not between lymph and serum. Penetration, as represented by the mean ratios of areas under the curve, was 19.7 +/- 8.1% to lymph and 38.2 +/- 11.7% to blister fluid. The flucloxacillin distribution volume during the phase of elimination was 36.4 +/- 16.0 liters and the total body clearance was 12.9 +/- 5.5 liters. Flucloxacillin showed good tissue penetration, considering its very high serum protein binding. High flucloxacillin levels in lymph and blister fluid were explained in part by drug affinity to extravascular albumin. The major impacts of high protein binding are (i) slightly slower passage into extravascular sites, (ii) slightly later peak concentration, and (iii) levels in extravascular fluid that are persistently below those in serum.

Antibiotic prophylaxis in pacemaker surgery: a prospective double blind trial with systemic administration of antibiotic versus placebo at implantation of cardiac pacemakers

In a double blind clinical trial, 106 consecutive patients scheduled for pacemaker implantation were randomly assigned either to a systemic prophylaxis group (SPG) (to be given flucloxacillin) or to a control group who would be given a placebo (CPG). The SPG group received 2 g IV flucloxacillin 1 hour before the operation, then 1 g perorally every 8 hours for the next five days. In the CPG group, placebo infusions and tablets were given at the same schedule. There were a total of 106 patients (SPG 52, CPG 54) who met the criteria of the study. Of these, 102 patients (SPG 50, CPG 52) completed a follow-up of 7-35 months. Infection of the pacemaker system was not diagnosed in any patient in either group. Tissue fluid was drawn 24 hours postoperatively from the pacemaker pocket for culture and for determination of pocket antibiotic concentration. The mean flucloxacillin concentration of pocket fluid from 23 patients in the SPG was 7.5 micrograms/ml. The bacteriological cultures were positive in 9/32 patients in the SPG group and in 10/34 patients in the CPG group. This study suggests that antibiotic prophylaxis need not routinely be given at implantation of permanent pacemaker systems.

[Clinical evaluation of flucloxacillin in the treatment of serious staphylococcal infections in children]

A total of twenty-nine children were admitted to the paediatric unit with confirmed or presumed staphylococcal infection and subsequently treated with the narrow spectrum antibiotic--flucloxacillin. Despite the gravity of their condition all but two patients made a satisfactory recovery. There were no side-effects associated with this treatment.