CLINICAL PHARMACOLOGY
Mechanism Of Action
Heparin
Heparin interacts with the naturally occurring plasma protein, Antithrombin III, to induce a conformational change, which markedly enhances the serine protease activity of Antithrombin III, thereby inhibiting the activated coagulation factors involved in the clotting sequence, particularly Xa and IIa. Small amounts of heparin inhibit Factor Xa, and larger amounts inhibit thrombin (Factor IIa).
Heparin also prevents the formation of a stable fibrin clot by inhibiting the activation of the fibrin stabilizing factor. Heparin does not have fibrinolytic activity; therefore, it will not lyse existing clots.
Taurolidine
Taurolidine is an antimicrobial drug [see Microbiology].
Pharmacodynamics
The pharmacodynamics of DEFENCATH are unknown.
Pharmacokinetics
No pharmacokinetic studies were conducted because DEFENCATH is intended to be instilled into the catheter lumens at the conclusion of each HD session for patients with kidney failure requiring chronic HD. DEFENCATH is not intended for systemic administration [see DOSAGE AND ADMINISTRATION].
Microbiology
Mechanism Of Action
The mechanism of action of taurolidine and its metabolites is non-specific, causing damage to microbial cell walls and inhibiting adherence of microorganisms to biological surfaces.
Resistance
Time kill studies showed that taurolidine is bactericidal (>3 log10 CFU reduction) at 1x to 4x minimum inhibitory concentration (MIC). The frequency of resistant mutants was <10-9 at 2x and 4x MIC for two strains each of Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Enterococcus faecium and Pseudomonas aeruginosa.1
Antimicrobial Activity
The following in vitro data are available but their clinical significance is unknown. Taurolidine has been shown to be active against most isolates of the following microorganisms:
Gram-Positive
Staphylococcus aureus (including methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA))
Staphylococcus epidermidis
Enterococcus faecalis
Gram-Negative
Escherichia coli
Klebsiella pneumoniae
Pseudomonas aeruginosa
Serratia marcescens
Fungi
Candida albicans
Candida glabrata
Clinical Studies
The efficacy and safety of DEFENCATH for reducing the incidence of CRBSI in patients with kidney failure receiving chronic HD was evaluated in LOCK-IT-100 (referred to as Trial 1, NCT02651428), a randomized, double-blind, active-controlled, multicenter trial.
A total of 806 patients were randomized in a 1:1 ratio to receive either DEFENCATH or heparin (heparin sodium USP 1,000 units/mL, benzyl alcohol 9.45 mg/mL and sodium chloride 9.0 mg/mL) as a CLS. Enrollment in Trial 1 was not limited to patients with specific types of HD catheters. DEFENCATH or heparin was instilled into central venous HD catheters at the end of all dialysis sessions and was withdrawn prior to the initiation of the next dialysis session. The median age of the study population was 63 years (range 21-94 years); 58% identified as males and 63% identified as white. The majority of patients (98%) had HD treatment three times per week, and 48% had their catheter implanted within three months prior to randomization.
A clinical adjudication committee (CAC) assessed the cases of CRBSI. The CAC definition for CRBSI included one positive blood culture (other than for coagulase-negative staphylococci, which required a confirmatory culture) from a peripheral site or either the arterial or venous catheter hub or the arterial or venous dialysis blood line and the patient had to have signs and symptoms of infection and no other apparent source of bloodstream infection.
Results of analyses of CAC-adjudicated CRBSI among the DEFENCATH and heparin groups in all randomized patients who received at least one dose of allocated study CLS are presented in Table 3. Patients in the DEFENCATH group had a lower incidence of CRBSI events compared to patients in the control group.
Table 3. Results of Analyses of CAC-Adjudicated CRBSI in Patients with Kidney Failure Receiving HD in Trial 1
|
DEFENCATH
(N=397) |
Heparin
(N=398) |
| CAC-adjudicated CRBSI |
9 (2.3%) |
32 (8.0%) |
| Event rate per 1000 catheter-days (95% CI) |
0.13 (0.07, 0.26) |
0.46 (0.33, 0.66) |
| Risk reduction (95% CI)* |
71% (38%, 86%) |
| Log-rank test p-value |
0.0006 |
| *Based on 1 – Hazard Ratio |
In total, 5% [18/397] of subjects in the DEFENCATH arm and 5% [21/398] of subjects in the heparin arm died during the trial (difference [DEFENCATH – Heparin]: -0.7% with a 95% CI[-3.7%, 2.3%]).
Among the 9 patients in the DEFENCATH arm with a CAC-adjudicated CRBSI, 1 had a gramnegative organism isolated and 8 had a gram-positive organism isolated; among the 32 patients in the heparin arm with a CAC-adjudicated CRBSI, 14 had a gram-negative organism isolated and 18 had a gram-positive organism isolated.
REFERENCES
1. Torres-Viera, C, Thauvin-Eliopoulos C., Souli M, DeGirolamin P, Farris MG, Wennerstein CB, Sofia RD and Eliopoulos GM. 2000. Antimicrobial Agents and Chemotherapy 44(6):1720 - 1724.