Pharmacokinetics and distribution of ticarcillin-clavulanic acid (Timentin) in experimental animals

Pleural penetration of amoxicillin and metronidazole during pleural infection: An ambispective cohort study

OBJECTIVES

The pharmacokinetics of antibiotics in pleural fluid during pleural infections has been poorly described. This study aimed to explore amoxicillin and metronidazole diffusion into the pleural space.

METHODS

This was an ambispective, single-centre study that included patients with complicated parapneumonic effusion or pleural empyema managed with repeated therapeutic thoracentesis as first-line treatment between 2014 and 2022. Pleural steady-state or trough concentrations of amoxicillin and metronidazole were measured, with a lower limit of quantification of 5 mg/L.

RESULTS

Seventy paired blood and pleural samples were analysed from 40 patients. The median (interquartile range) patient age was 55 years (45-67 years) and 88% were male. The median patient weight was 65.8 kg (57.3-82 kg) and median plasma albumin concentration was 29.7 g/L (23.7-33.9 g/L). Median creatinine clearance was 106 mL/min (95-117 mL/min). Median amoxicillin pleural concentrations in patients treated with oral, bolus and continuous intravenous administrations (6 g/day) were, respectively, 5.2 (<5-6.4), 9.4 (8-13.1) and 10.8 (7.1-13.1) mg/L. Pleural concentrations were <5 mg/L in 5/11 samples (45%) with oral treatment and 6/59 (10%) with intravenous treatment. Median metronidazole pleural concentrations were 18.4 (15.7-22.8) mg/L, with all patients being treated orally (1.5 g/day).

CONCLUSIONS

Oral metronidazole (1.5 g/day) and intravenous amoxicillin (6 g/day) achieved therapeutic targets in pleural fluid in most cases, but oral amoxicillin did not.

Binding of temocillin to plasma proteins in vitro and in vivo: the importance of plasma protein levels in different populations and of co-medications

BACKGROUND

Temocillin plasma protein binding (PPB) in healthy individuals is reported to be ∼85% but had not been studied in patients.

OBJECTIVES

To obtain normative data on temocillin PPB in patients in relation to infection and impact of co-medications widely used in ICU.

METHODS

Plasma was obtained from healthy individuals (Group #1), non-ICU patients with UTI (Group #2), ICU patients with suspected/confirmed ventriculitis (Group #3) or with sepsis/septic shock (Group #4). Total and unbound temocillin concentrations were measured in spiked samples from temocillin-naive donors (in vitro) or in plasma from temocillin-treated subjects (in vivo). The impact of diluting plasma, using pharmaceutical albumin, or adding drugs potentially competing for PPB was tested in spiked samples. Data were analysed using a modified Hill-Langmuir equation taking ligand depletion into account.

RESULTS

Temocillin PPB was saturable in all groups, both in vitro and in vivo. Maximal binding capacity (Bmax) was 1.2-2-fold lower in patients. At 20 and 200 mg/L (total concentrations), the unbound fraction reached 12%-29%, 23%-42% and 32%-52% in Groups #2, #3, #4. The unbound fraction was inversely correlated with albumin and C-reactive protein concentrations. Binding to albumin was 2-3-fold lower than in plasma and non-saturable. Drugs with high PPB but active at lower molar concentrations than temocillin caused minimal displacement, while fluconazole (low PPB but similar plasma concentrations to temocillin) increased up to 2-fold its unbound fraction.

CONCLUSIONS

Temocillin PPB is saturable, 2-4-fold lowered in infected patients in relation to disease severity (ICU admission, hypoalbuminaemia, inflammation) and only partially reproducible with albumin. Competition with other drugs must be considered for therapeutic concentrations to be meaningful.

In vitro susceptibilities of feline and canine Escherichia coli and Pseudomonas spp. isolates to ticarcillin and ticarcillin-clavulanic acid

OBJECTIVES

To investigate in vitro susceptibilities of canine and feline Escherichia coli and canine Pseudomonas spp. isolates to ticarcillin and ticarcillin-clavulanic acid (T/C).

DESIGN

In vitro susceptibility testing of bacterial isolates collected from infections.

METHODS

We tested 148 (83 canine and 65 feline) E. coli and 61 canine Pseudomonas spp. isolates for susceptibility to T/C using both disc diffusion and Epsilometer tests (E-tests). Additionally, susceptibilities of 96 E. coli and 23 canine Pseudomonas spp. isolates were tested via disc diffusion to ticarcillin alone.

RESULTS

Of the E. coli isolates obtained from canine and feline urine, 92% by disc diffusion and 91% by E-tests were susceptible to T/C. Of the canine Pseudomonas isolates, 90% by disc diffusion and 82% by E-tests were susceptible to T/C. Of the Pseudomonas spp. isolates from the canine ear canal or tympanic bullae, 12% of isolates tested via disc diffusion and 23% via E-tests were found to be resistant to T/C. The 50% minimum inhibitory concentration of T/C for all feline E. coli isolates was significantly lower than that for all canine E. coli isolates (P = 0.0031). The addition of clavulanic acid significantly increased the efficacy of ticarcillin against E. coli (P< 0.0001), but had negligible effect against canine Pseudomonas spp. isolates.

CONCLUSION

Ticarcillin-clavulanic acid has reasonable in vitro efficacy against canine and feline E. coli, and canine Pseudomonas spp. isolates. However, decisions to use this drug therapeutically must be made on prudent considerations to minimise selection for bacterial resistance.

Scaling basic toxicokinetic parameters from rat to man

Scaling of the quantified dispositional parameters of xenobiotics from animals to man is of interest from the standpoint of toxicology (e.g., poisoning and risk assessment). Scaling is also important from the standpoint of therapeutics because it represents a strategy for predicting first-use-in-human doses in clinical trials of investigational new drugs. Current strategies for scaling either doses of xenobiotics or the dispositional parameters of xenobiotics from animals to man rely on models that take account principally of species differences in weight or body surface area. Interspecies scaling of dispositional parameters such as clearance or volume of distribution commonly involves the comparison of estimates of these parameters for a given xenobiotic among numerous species on the basis of weight with the resultant mathematical relationship used to predict the values of those parameters for that xenobiotic in a species weighing, on average, about 70 kg (i.e., a man). Our approach has been to ascertain whether a useful mathematical model could be developed for predicting the dispositional parameters of a xenobiotic, its half-life and volume of distribution, in humans based exclusively on estimates of those parameters in rats. Based on a data set of about 100 different xenobiotics, we found that values for half-life and volume of distribution of a xenobiotic in humans can be predicted from the estimates of those parameters in rats.

Pharmacokinetics and bioavailability of ticarcillin and clavulanate in foals after intravenous and intramuscular administration

The pharmacokinetics and bioavailability of ticarcillin and clavulanate were determined after intravenous (i.v.) or intramuscular (i.m.) administration of ticarcillin disodium (50 mg/kg) combined with clavulanate potassium (1.67 mg/kg) to groups of healthy foals at 3 days and 28 days of age. After i.v. administration of the combination to five foals, the disposition kinetics of ticarcillin and clavulanate were best described using a two-compartment open model. Mean plasma elimination-rate constant (beta) and clearance (ClB) for ticarcillin were significantly less (P less than 0.01), and volume of distribution at steady state (Vd(ss)) was significantly larger (P less than 0.05), in the foals at 3 days compared with 28 days of age. This indicated that renal excretion mechanisms were immature and ticarcillin was more widely distributed in 3-day-old foals. The mean elimination rate constant for clavulanate was significantly less (P less than 0.01) at 3 days than at 28 days of age. Values of the major kinetic terms describing the disposition of ticarcillin after i.m. administration to five 3-day-old foals were not significantly different from values of these parameters in the same foals at 28 days of age. After i.m. administration of the drug combination, plasma clavulanate concentrations peaked significantly later (P less than 0.01), and the elimination-rate constant (kd) for clavulanate was significantly less (P less than 0.01), in 3-day-old foals than in 28-day-old foals. The bioavailabilities of ticarcillin and clavulanate after i.m. administration in 3-day-old foals were 100% and 88.3%, respectively, and in 28-day-old foals were 100% and 27.4%, respectively. Mean plasma ticarcillin concentrations exceeded 16 micrograms/ml for a longer period after i.m. administration of the drug combination than after i.v. administration to foals of both age groups. By virtue of the frequency of administration required and the painful response elicited by i.m. injection, it is recommended that when the combination of ticarcillin disodium (50 mg/kg) and clavulanate potassium (1.67 mg/kg) is used in foals to treat infections caused by susceptible organisms (MIC less than or equal to 16 micrograms/ml), it should be administered i.v. four times daily.

Evaluation of piperacillin-tazobactam in experimental meningitis caused by a beta-lactamase-producing strain of K1-positive Escherichia coli

We evaluated the pharmacokinetics and therapeutic efficacy of piperacillin combined with tazobactam, a novel beta-lactamase inhibitor, in experimental meningitis due to a beta-lactamase-producing strain of K1-positive Escherichia coli. Different doses of piperacillin and tazobactam, as single agents and combined (8:1 ratio; dosage range, 40/5 to 200/25 mg/kg per h), and of ceftriaxone were given to experimentally infected rabbits by intravenous bolus injection followed by a 5-h constant infusion. The mean (+/- standard deviation) rates for penetration into the cerebrospinal fluid of infected animals after coadministration of both drugs were 16.6 +/- 8.4% for piperacillin and 32.5 +/- 12.6% for tazobactam. Compared with either agent alone, combination treatment resulted in significantly better bactericidal activity in the cerebrospinal fluid. The bactericidal activity of piperacillin-tazobactam was dose dependent: cerebrospinal fluid bacterial titers were reduced by 0.37 +/- 0.19 log10 CFU/ml per h with the lowest dose versus 0.96 +/- 0.25 log10 CFU/ml per h with the highest dose (P less than 0.001). At the relatively high doses of 160/20 and 200/25 mg of piperacillin-tazobactam per kg per h, the bactericidal activity of the combination was comparable to that of 10 and 25 mg of ceftriaxone per kg per h, respectively.

Simulation of human serum pharmacokinetics of ticarcillin-clavulanic acid and ceftazidime in rabbits, and efficacy against experimental Klebsiella pneumoniae meningitis

The penetration into cerebrospinal fluid (CSF) and efficacy of ticarcillin-clavulanic acid, ticarcillin alone, and ceftazidime were compared in rabbits with experimentally induced Klebsiella pneumoniae meningitis. The compounds were administered to simulate in rabbit plasma the concentration-versus-time curves observed in humans after 30-min infusions of Timentin (3 g of ticarcillin plus 100 mg of clavulanic acid), ticarcillin (3 g), and ceftazidime (2 g). Single- and multiple-dosing schedules were used. The penetrations of clavulanic acid into CSF (expressed as [area under the concentration-time curve for CSF/area under the curve for plasma] x 100) after the two dosing schedules were 28 and 24.5%, similar to that for ceftazidime (21%; multiple-dosing only) and greater than those for ticarcillin (8.4 and 9.3%). Ticarcillin was ineffective in reducing viable counts in CSF but, in the presence of clavulanic acid, reduced bacterial numbers by approximately 99% at 4 h after a single dose and by 99.99% at 12 h after three doses given at 4-h intervals. Two doses of ceftazidime given 8 h apart were more effective than the three doses of ticarcillin-clavulanic acid, in keeping with the in vitro activities of these compounds against the infecting organism. These results illustrate the ability of clavulanic acid to penetrate the blood-CSF barrier such that concentrations of the inhibitor in CSF potentiate the activity of ticarcillin against the ticarcillin-resistant, beta-lactamase-producing strain of K. pneumoniae.