Serum levels and clinical effect of flucloxacillin in patients with staphylococcal infections

Do dietary interventions exert clinically important effects on the bioavailability of β-lactam antibiotics? A systematic review with meta-analyses

BACKGROUND

Managing drug-food interactions may help to achieve the optimal action and safety profile of β-lactam antibiotics.

METHODS

We conducted a systematic review with meta-analyses in adherence to PRISMA guidelines for 32 β-lactams. We included 166 studies assessing the impact of food, beverages, antacids or mineral supplements on the pharmacokinetic (PK) parameters or PK/pharmacodynamic (PK/PD) indices.

RESULTS

Eighteen of 25 β-lactams for which data on food impact were available had clinically important interactions. We observed the highest negative influence of food (AUC or Cmax decreased by >40%) for ampicillin, cefaclor (immediate-release formulations), cefroxadine, cefradine, cloxacillin, oxacillin, penicillin V (liquid formulations and tablets) and sultamicillin, whereas the highest positive influence (AUC or Cmax increased by >45%) for cefditoren pivoxil, cefuroxime and tebipenem pivoxil (extended-release tablets). Significantly lower bioavailability in the presence of antacids or mineral supplements occurred for 4 of 13 analysed β-lactams, with the highest negative impact for cefdinir (with iron salts) and moderate for cefpodoxime proxetil (with antacids). Data on beverage impact were limited to 11 antibiotics. With milk, the extent of absorption was decreased by >40% for cefalexin, cefradine, penicillin G and penicillin V, whereas it was moderately increased for cefuroxime. No significant interaction occurred with cranberry juice for two tested drugs (amoxicillin and cefaclor).

CONCLUSIONS

Factors such as physicochemical features of antibiotics, drug formulation, type of intervention, and patient's health state may influence interactions. Due to the poor actuality and diverse methodology of included studies and unproportionate data availability for individual drugs, we judged the quality of evidence as low.

Interventions for bacterial folliculitis and boils (furuncles and carbuncles)

BACKGROUND

Bacterial folliculitis and boils are globally prevalent bacterial infections involving inflammation of the hair follicle and the perifollicular tissue. Some folliculitis may resolve spontaneously, but others may progress to boils without treatment. Boils, also known as furuncles, involve adjacent tissue and may progress to cellulitis or lymphadenitis. A systematic review of the best evidence on the available treatments was needed.

OBJECTIVES

To assess the effects of interventions (such as topical antibiotics, topical antiseptic agents, systemic antibiotics, phototherapy, and incision and drainage) for people with bacterial folliculitis and boils.

SEARCH METHODS

We searched the following databases up to June 2020: the Cochrane Skin Specialised Register, CENTRAL, MEDLINE, and Embase. We also searched five trials registers up to June 2020. We checked the reference lists of included studies and relevant reviews for further relevant trials.  SELECTION CRITERIA: We included randomised controlled trials (RCTs) that assessed systemic antibiotics; topical antibiotics; topical antiseptics, such as topical benzoyl peroxide; phototherapy; and surgical interventions in participants with bacterial folliculitis or boils. Eligible comparators were active intervention, placebo, or no treatment.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Our primary outcomes were 'clinical cure' and 'severe adverse events leading to withdrawal of treatment'; secondary outcomes were 'quality of life', 'recurrence of folliculitis or boil following completion of treatment', and 'minor adverse events not leading to withdrawal of treatment'. We used GRADE to assess the certainty of the evidence.

MAIN RESULTS

We included 18 RCTs (1300 participants). The studies included more males (332) than females (221), although not all studies reported these data. Seventeen trials were conducted in hospitals, and one was conducted in clinics. The participants included both children and adults (0 to 99 years). The studies did not describe severity in detail; of the 232 participants with folliculitis, 36% were chronic. At least 61% of participants had furuncles or boils, of which at least 47% were incised. Duration of oral and topical treatments ranged from 3 days to 6 weeks, with duration of follow-up ranging from 3 days to 6 months. The study sites included Asia, Europe, and America. Only three trials reported funding, with two funded by industry. Ten studies were at high risk of 'performance bias', five at high risk of 'reporting bias', and three at high risk of 'detection bias'. We did not identify any RCTs comparing topical antibiotics against topical antiseptics, topical antibiotics against systemic antibiotics, or phototherapy against sham light. Eleven trials compared different oral antibiotics. We are uncertain as to whether cefadroxil compared to flucloxacillin (17/21 versus 18/20, risk ratio (RR) 0.90, 95% confidence interval (CI) 0.70 to 1.16; 41 participants; 1 study; 10 days of treatment) or azithromycin compared to cefaclor (8/15 versus 10/16, RR 1.01, 95% CI 0.72 to 1.40; 31 participants; 2 studies; 7 days of treatment) differed in clinical cure (both very low-certainty evidence). There may be little to no difference in clinical cure rate between cefdinir and cefalexin after 17 to 24 days (25/32 versus 32/42, RR 1.00, 95% CI 0.73 to 1.38; 74 participants; 1 study; low-certainty evidence), and there probably is little to no difference in clinical cure rate between cefditoren pivoxil and cefaclor after 7 days (24/46 versus 21/47, RR 1.17, 95% CI 0.77 to 1.78; 93 participants; 1 study; moderate-certainty evidence). For risk of severe adverse events leading to treatment withdrawal, there may be little to no difference between cefdinir versus cefalexin after 17 to 24 days (1/191 versus 1/200, RR 1.05, 95% CI 0.07 to 16.62; 391 participants; 1 study; low-certainty evidence). There may be an increased risk with cefadroxil compared with flucloxacillin after 10 days (6/327 versus 2/324, RR 2.97, 95% CI 0.60 to 14.62; 651 participants; 1 study; low-certainty evidence) and cefditoren pivoxil compared with cefaclor after 7 days (2/77 versus 0/73, RR 4.74, 95% CI 0.23 to 97.17; 150 participants; 1 study; low-certainty evidence). However, for these three comparisons the 95% CI is very wide and includes the possibility of both increased and reduced risk of events. We are uncertain whether azithromycin affects the risk of severe adverse events leading to withdrawal of treatment compared to cefaclor (274 participants; 2 studies; very low-certainty evidence) as no events occurred in either group after seven days. For risk of minor adverse events, there is probably little to no difference between the following comparisons: cefadroxil versus flucloxacillin after 10 days (91/327 versus 116/324, RR 0.78, 95% CI 0.62 to 0.98; 651 participants; 1 study; moderate-certainty evidence) or cefditoren pivoxil versus cefaclor after 7 days (8/77 versus 5/73, RR 1.52, 95% CI 0.52 to 4.42; 150 participants; 1 study; moderate-certainty evidence). We are uncertain of the effect of azithromycin versus cefaclor after seven days due to very low-certainty evidence (7/148 versus 4/126, RR 1.26, 95% CI 0.38 to 4.17; 274 participants; 2 studies). The study comparing cefdinir versus cefalexin did not report data for total minor adverse events, but both groups experienced diarrhoea, nausea, and vaginal mycosis during 17 to 24 days of treatment. Additional adverse events reported in the other included studies were vomiting, rashes, and gastrointestinal symptoms such as stomach ache, with some events leading to study withdrawal. Three included studies assessed recurrence following completion of treatment, none of which evaluated our key comparisons, and no studies assessed quality of life.

AUTHORS' CONCLUSIONS

We found no RCTs regarding the efficacy and safety of topical antibiotics versus antiseptics, topical versus systemic antibiotics, or phototherapy versus sham light for treating bacterial folliculitis or boils. Comparative trials have not identified important differences in efficacy or safety outcomes between different oral antibiotics for treating bacterial folliculitis or boils. Most of the included studies assessed participants with skin and soft tissue infection which included many disease types, whilst others focused specifically on folliculitis or boils. Antibiotic sensitivity data for causative organisms were often not reported. Future trials should incorporate culture and sensitivity information and consider comparing topical antibiotic with antiseptic, and topical versus systemic antibiotics or phototherapy.

Probenecid and food effects on flucloxacillin pharmacokinetics and pharmacodynamics in healthy volunteers

OBJECTIVES

To measure the effect of probenecid, fasting and fed, on flucloxacillin pharmacokinetic and pharmacodynamic endpoints.

METHODS

Flucloxacillin 1000 mg orally was given to 11 volunteers alone while fasting ('flucloxacillin alone'), and with probenecid 500 mg orally while fasting ('probenecid fasting') and with food ('probenecid fed'). Flucloxacillin pharmacokinetic and pharmacodynamic endpoints were compared.

RESULTS

Probenecid, fasting and fed, increased free plasma flucloxacillin area under the concentration-time curve (zero to infinity) ∼1.65-fold (p < 0.01) versus flucloxacillin alone. Probenecid fed prolonged time to peak flucloxacillin concentrations ∼2-fold versus the other two regimens (p < 0.01). Probenecid fasting or fed increased free flucloxacillin concentrations exceeding 30%, 50% and 70% of the first 6, 8 and 12 h post-dose by 1.58- to 5.48-fold compared with flucloxacillin alone. As an example of this pharmacodynamic improvement, the probability of target attainment of free concentrations above the minimum inhibitory concentration for Staphylococcus aureus (0.5 mg/L) for 50% of a 6-hour dose interval was > 80% for flucloxacillin plus probenecid (fasting or fed) and < 20% for flucloxacillin alone.

CONCLUSIONS

Probenecid increased flucloxacillin exposure, with predicted pharmacodynamic effects greater than pharmacokinetic effects because of the altered shape of the concentration-time curve. Probenecid may improve the applicability of oral flucloxacillin regimens.

In healthy volunteers, taking flucloxacillin with food does not compromise effective plasma concentrations in most circumstances

It is usually recommended that flucloxacillin is given on an empty stomach. The aim of this study was to compare total and free flucloxacillin concentrations after oral flucloxacillin, given with and without food, based on contemporary pharmacokinetic and pharmacodynamic targets. Flucloxacillin 1000 mg orally was given to 12 volunteers, after a standardised breakfast and while fasting, on two separate occasions. Flucloxacillin concentrations over 12 hours were measured by liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters, and pharmacodynamic endpoints related to target concentration achievement, were compared in the fed and fasting states. For free flucloxacillin, the fed/fasting area under the concentration-time curve from zero to infinity (AUC0-∞) ratio was 0.80 (p<0.01, 90% CI 0.70-0.92), the peak concentraton (Cmax) ratio 0.51 (p<0.001, 0.42-0.62) and the time to peak concentration (Tmax) ratio 2.2 (p<0.001, 1.87-2.55). The ratios for total flucloxacillin concentrations were similar. The mean (90% CI) fed/fasting ratios of free concentrations exceeded for 30%, 50% and 70% of the first 6 hours post-dose were 0.74 (0.63-0.87, fed inferior p<0.01), 0.95 (0.81-1.11, bioequivalent) and 1.15 (0.97-1.36, fed non-inferior), respectively. Results for 8 hours post-dose and those predicted for steady state were similar. Comparison of probability of target attainments for fed versus fasting across a range of minimum inhibitory concentrations (MICs) were in line with these results. Overall, this study shows that food reduced the AUC0-∞ and Cmax, and prolonged the Tmax of both free and total flucloxacillin concentrations compared with the fasting state, but achievement of free concentration targets associated with efficacy was in most circumstances equivalent. These results suggest that taking flucloxacillin with food is unlikely to compromise efficacy in most circumstances.

Pharmacokinetics and bioavailability of flucloxacillin in elderly hospitalized patients

The pharmacokinetics and oral bioavailability of flucloxacillin were studied in five female and two male patients (age 68-87 yr) who had been hospitalized for orthopedic surgeries. A single dose of intravenous or oral flucloxacillin sodium (500 mg) was administered in random order on different occasions separated by at least 2 days. Blood and urine samples were taken up to 24 hours after drug administration and levels of flucloxacillin and 5-hydroxymethylflucloxacillin (5-HMF), a major metabolite, were measured by high-performance liquid chromatography. Flucloxacillin elimination, but not oral absorption, was reduced in the elderly, compared with data from young healthy subjects reported elsewhere. Total clearance, renal clearance, and volume of distribution were 0.083 +/- 0.013 L/kg/hr, 0.038 +/- 0.01 L/kg/hr, and 0.184 +/- 0.034 L/kg, respectively. Regression of flucloxacillin renal clearance (Clr) on estimated creatine clearance (CLcr) gave the relationship: Clr = 0.755 (CLcr) + 10.6 (r = 0.91; P = 0.004). Terminal half-lives for flucloxacillin and 5-HMF were 2.21 +/- 0.51 hr and 3.0 +/- 0.75 hr, respectively after intravenous administration. Flucloxacillin was absorbed rapidly after oral administration with a mean absorption time of 0.95 +/- 0.34 hr, and time to reach peak concentration of 1.20 +/- 0.29 hr. The absolute bioavailability of flucloxacillin from capsules was 54.4 +/- 18.8%.

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.

Oral absorption of flucloxacillin in infants and young children

The bioavailability of flucloxacillin (Heracillin) following oral administration was determined in infants and children. After a dose of 12.5 mg/kg, peak concentrations were achieved at 60 min. which declined rapidly and were low in older children only 4 hours afterwards. Infants below 6 months of age showed a better absorption when given the mixture than older children. Older children achieved higher plasma concentrations when given tablets than when given equal doses of the mixture. There was no difference in the concentration when the dose was given to the subject when fasting, or with breakfast.

Characterization of Staphylococcus aureus isolates from oral surgical outpatients compared to isolates from hospitalized and non-hospitalized individuals

In 160 patients, 114 strains of Staphylococcus aureus were isolated from gingival mucosa, saliva, throat and nose. The patients were divided into 4 groups: one group from an oral surgery clinic for outpatients, one group from a dental clinic, one group from a general surgery clinic for inpatients and one group from a clinic for chronically ill and aged patients. The highest frequency of staphylococcal carriers was found in the outpatient groups (oral surgery and dental clinic), 55% and 45%, respectively. Antibiotic sensitivity testing revealed the majority of the strains to be penicillin resistant, but sensitive to isoxazolyl-penicillins, clindamycin and lincomycin. 50% of the strains produced penicillinase. About 90% of all strains produced lipase, nuclease and a haemolysin most active on rabbit erythrocytes. Human and sheep erythrocytes were lysed by 70% and 46% of the strains, respectively. 77% of the strains were bacteriolytic active. No strain produced lecitinase or elastase. No significant difference was found between the 4 groups in the formation of any of these factors. Phage-type I and III dominated but there was no correlation to enzyme production or patient groups. Thus the 4 patient groups were colonized with strains of Staphylococcus aureus that showed mainly the same pathogenetic factors.

Dicloxacillin and flucloxacillin twice daily with probenecid in staphylococcal infections. A clinical and pharmakokinetic evaluation

The therapeutic efficacy of decloxacillin or flucloxacillin, 1--2 g orally with probenecid twice daily was evaluated in staphylococcal infections. Excellent results were obtained with this as long-term maintenance therapy in 4 patients with relapsing chronic osteomyelitis and in 6 patients with postoperative infections. No side effects were observed in these patients. In 35 patients with furunculosis twice daily administration of dicloxacillin was used as a primary therapeutic regimen. All healed, but 4 recurrencies occurred during a 3-month observation period after therapy. In 5 patients allergic reactions were noted. The unbound fraction of flucloxallin in serum exceeded MIC values of methicillin-susceptible Staphylococcus aureus during 11 of 24 h. Pharmacokinetic data on flucloxallin with and without probenecid are given.