Argaron

Anticoagulation in adult patients with heparin-induced thrombocytopenia type II who require parenteral antithrombotic therapy.

The diagnosis should be confirmed by the HIPAA (heparin induced platelet activation assay) or an equivalent test. However, such confirmation must not delay the start of treatment.

Paediatric population

Initial Dosage

Treatment with Argaron should be initiated under the guidance of a physician with experience in coagulation disorders.

The initial dosage in adult patients without hepatic impairment in HIT type II is 2 microgram/kg/min, administered as a continuous infusion (see Method of Administration). Before Argaron is administered, heparin therapy should be discontinued and a baseline aPTT value obtained.

Standard recommendations

Monitoring:

In general, therapy with Argaron is monitored using the activated partial thromboplastin time (aPTT).

Tests of anticoagulant effects (including the aPTT) attain steady-state levels typically within 1-3 hours following initiation of Argaron.

The target range for steady-state aPTT is 1.5-3.0 times the initial baseline value, but not exceeding 100 seconds.

Dose adjustment may be required to attain the target aPTT (see Dose Modifications).

aPTT should be checked two hours after the start of the infusion to confirm that the aPTT is within the desired therapeutic range. Thereafter, the aPTT should be monitored at least once per day.

Dose modifications:

After the initial dose of Argaron, the dose can be adjusted based on the clinical course until the steady-state aPTT is within the desired therapeutic range (1.5 to 3.0 times the initial baseline value but not exceeding 100 seconds). In case of an elevated aPTT (greater than 3 times baseline or 100 seconds), the infusion should be discontinued until the aPTT is within the desired range of 1.5 to 3 times baseline (typically within 2 hours of discontinuation of infusion), and the infusion restarted at one half of the previous infusion rate. The aPTT should be checked again after 2 hours.

The maximum recommended dose is 10 microgram/kg/min. The maximum recommended duration of treatment is 14 days, although there is limited clinical experience of administration for longer periods.

Method of administration

Argaron is supplied as a 1 mg/ml ready to use solution for intravenous infusion (50 mg/50 ml. It is recommended for use with a syringe driver to control the rate of administration.

Standard infusion rates for the 2 microgram/kg/min recommended initial dosage (1 mg/ml concentration) are detailed in the table below. The standard infusion rates for patients with moderate hepatic impairment (Child-Pugh Class B), after cardiac surgery and critically ill patients with a starting infusion rate of 0.5 microgram/kg/min are also detailed in the table below:

Additional Information on Special Populations:

Older people

The standard initial dosage recommendations for use in adults are applicable to elderly patients.

Paediatric population

Limited data from a prospective clinical study in 18 children (neonates to 16 years old) and published data is available. The safe and effective dose or the effective target range for aPTT or activated clotting time (ACT) of Argaron has not been clearly established in this patient population.2 but no recommendation on a posology can be made.

Renal impairment

The standard initial dosage recommendations for use in adults are applicable to patients with renal impairment.

Limited data is available from the use of Argaron in haemodialysis. Based on the data, therapy could be initiated with an initial bolus (250 microgram/kg) followed by continuous infusion of 2 microgram/kg/min. The infusion is stopped 1 hour before the end of the procedure. The target ACT range is 170-230 seconds (measured using the Haemotec device).

In patients that are already being treated with Argaron no bolus dose is required. Argaron clearance by high flux membranes used during haemodialysis and continuous venovenous haemofiltration was clinically insignificant.

Hepatic impairment

For patients with moderate hepatic impairment (Child-Pugh Class B), an initial dose of 0.5 microgram/kg/min is recommended. The aPTT should be monitored closely and the dosage should be adjusted as indicated clinically. Argaron is contra-indicated in patients with severely impaired liver function.

Patients with HIT Type II after cardiac surgery and critically ill patients

Limited data is available from the use of Argaron in patients with HIT Type II after cardiac surgery and critically ill patients / intensive care unit (ICU) patients with (multiple) organ system failure. Based on the data therapy could be initiated with a starting infusion rate of 0.5 microgram/kg/min (maximum 10 microgram/kg/min) and adjusted to the target aPTT range of 1.5-3.0 times baseline value (not exceeding 100 seconds).

In critically ill/ICU patients with severe (multiple) organ failure (as assessed by SOFA-II APACHE-II or comparable scores) a reduced maintenance dose is recommended.

The clinical status of the patient, especially acute changes in hepatic function, should be taken into account and the infusion rate should be carefully adjusted to maintain the aPTT in the desired range.

An increase in the frequency of monitoring is recommended to ensure the target aPTT values are achieved and maintained.

Patients with HIT Type II undergoing percutaneous coronary intervention (PCI)

Limited data is available from the use of Argaron in patients with HIT Type II undergoing percutaneous coronary intervention. Based on the data, when there is no alternative, therapy could be initiated with a bolus dose of 350 microgram/kg over 3 to 5 minutes followed by an infusion dose of 25 microgram/kg/min. ACT should be checked 5 to 10 minutes after the bolus dose is completed. The procedure may proceed if the ACT is greater than 300 sec. If the ACT is below 300 sec, an additional bolus dose of 150 microgram/kg should be administered, the infusion rate be increased to 30 microgram/kg/min, and the ACT should be checked 5 to 10 minutes later. If the ACT is higher than 450 sec, the infusion rate should be decreased to 15 microgram/kg/min and ACT values be checked 5 to 10 minutes later. Once a therapeutic ACT between 300 to 450 sec has been achieved, the infusion dose should be continued for the duration of the procedure. ACT measurements were recorded using both Haemotec and Haemochrom devices.

The efficacy and safety of Argaron use in combination with GPIIb/IIIa inhibitors has not been established.

NOTE: 1 mg/ml = 1000 microgram (mcg)/ml

†Additional IV bolus dose of 150 mcg/kg should be administered if ACT <300 seconds.

Specific dosing information on patients with hepatic impairment undergoing PCI is not available. Therefore, the use of Argaron for treatment of patients with hepatic impairment requiring PCI is not recommended.

Recommendations for use in patients scheduled for a conversion to oral anticoagulation

Use of oral anticoagulants (of the coumarin type) should be delayed until substantial resolution of thrombocytopaenia (e.g. platelets >100 x 10⁹/l) to avoid coumarin associated microvascular thrombosis and venous limb gangrene. The intended maintenance dose should be started with no loading dose.

For both the Quick and Owren type PT assays;

Co-therapy of Argaron and oral anticoagulants (of the coumarin type) is recommended for a minimum of 5 days. INR should be measured daily while Argaron and oral anticoagulants are co-administered. On co-therapy the target value for INR should be within the therapeutic range according to the type of assay used (see above) for at least 2 days before Argaron is discontinued.

The INR measurement should be repeated 4-6 hours after discontinuation of Argaron. If the repeat INR is below the desired therapeutic range, the infusion of Argaron should be resumed and the procedure repeated daily until the desired therapeutic range on oral anticoagulants alone is reached.

For doses greater than 2 microgram/kg/min, the relationship between INR on oral anticoagulants alone or INR on oral anticoagulants plus Argaron is less predictable. With such higher doses, the dose of Argaron should be temporarily reduced to 2 microgram/kg/min in order to improve the prediction of INR on oral anticoagulants alone (see above). The INR on Argaron and oral anticoagulants should be measured 4 to 6 hours after reduction of the Argaron dose.

Argaron is contraindicated in patients with uncontrolled bleeding. Hypersensitivity to argatroban or to any of the excipients. Severe hepatic impairment.

Argaron causes a generally increased tendency to bleeding. An unexplained fall in haematocrit, fall in blood pressure, or any other unexplained symptom should lead to consideration of a haemorrhagic event.

Argaron should be used with extreme caution in disease states and other circumstances in which there is an increased danger of haemorrhage. These include treatment for severe hypertension; diabetic retinopathy; immediately following lumbar puncture; spinal anaesthesia; major surgery, especially involving the brain, spinal cord, or eye; haematological conditions associated with increased bleeding tendencies such as congenital or acquired bleeding disorders and gastrointestinal lesions such as ulcerations.

Parenteral anticoagulants: All parenteral anticoagulants should be discontinued before administration of Argaron. When Argaron is to be started after cessation of heparin therapy, sufficient time should be allowed for the effect of heparin on the aPTT to decrease prior to start of Argaron therapy (about 1-2 hours).

Hepatic Impairment: Caution should be exercised when administering Argaron to patients with hepatic disease, by starting with a lower dose and carefully titrating until the desired level of anticoagulation is achieved. Also, upon cessation of Argaron infusion in the hepatically-impaired patient, full reversal of anticoagulant effects may require longer than 4 hours due to decreased clearance of argatroban.

Laboratory Tests: Measurements of aPTT are recommended for monitoring the infusion. Although other plasma coagulation tests including prothrombin time (PT, expressed for example as the International Normalized Ratio (INR)), the activated clotting time (ACT) and thrombin time (TT) are affected by Argaron; the therapeutic ranges for these tests have not been defined. Plasma argatroban concentrations also correlate well with the anticoagulant effects.

The concomitant use of Argaron and oral anticoagulants may result in prolongation of the PT (INR) beyond that produced by oral anticoagulants alone.

Ethanol: Argaron contains ethanol. A 70kg patient administered the maximum recommended daily dose (10 microgram/kg/min) would receive a dose of approximately 4g ethanol per day.

This medicinal product contains sorbitol. Patients with rare hereditary problems of fructose intolerance should not use this medicinal product.

There is no specific antidote to Argaron.

In theory, the presence of ethanol in the formulation (200 mg per vial) may impair the patient's ability to drive or operate machinery. However, this is unlikely to be of clinical relevance in patients receiving Argaron.

Bleeding complications, as is to be expected given the pharmacological properties, constitute the main adverse events. In the clinical trials involving patients with HIT type II anticoagulated with Argaron, the incidence of major bleeds was 31/568 (5.5%) and minor bleeds 221/568 (38.9%). The incidence of major bleeds was almost three times higher in those patients in whom the aPTT level exceeded more than three times the baseline value than in those whose aPTT was within the therapeutic range. Dosage of Argaron should be adjusted to achieve a target aPTT level of 1.5-3.0 x baseline not exceeding 100 seconds.

The incidence of adverse reactions in clinical trials (568 patients with HIT Type II) which are considered to be possibly related to Argaron is stated below.

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme, Website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.

Excessive anticoagulation, with or without bleeding, may be controlled by discontinuing Argaron or by decreasing the infusion rate. In clinical studies, anticoagulation parameters return to baseline generally within 2 to 4 hours after discontinuation of Argaron. Reversal of anticoagulant effect may take longer in patients with hepatic impairment.

No specific antidote to Argaron is available. If life-threatening bleeding occurs and excessive plasma levels of argatroban are suspected, Argaron should be discontinued immediately and aPTT and other coagulation tests should be performed. Symptomatic and supportive therapy should be provided to the patient.

Lethal single intravenous doses of argatroban for mice, rats, rabbits, and dogs were 200, 124, 150, and 200 mg/kg respectively. The symptoms of acute toxicity were loss of righting reflex, tremors, clonic convulsions, paralysis of hind limbs, and coma.

Each vial contains 200 mg ethanol.

Pharmacotherapeutic group: Antithrombotic agents, direct thrombin inhibitors.

ATC code: B01AE03.

Mechanism of Action

Argatroban, a synthetic L-arginine derivative, is a direct thrombin inhibitor (molecular weight 526.65) that binds reversibly to thrombin. Argatroban exerts its anticoagulant effect independently of antithrombin III and inhibits fibrin formation; activation of coagulation factors V, VIII and XIII; activation of protein C; and platelet aggregation.

Pharmacodynamic effects

Argatroban is highly selective for thrombin; inhibitory constant (Ki) values in studies in vitro with synthetic tripeptides ranged from 5 to 39 nM.

Argatroban is capable of inhibiting the action of both free and clot-associated thrombin. It does not interact with heparin-induced antibodies. There was no evidence of formation of antibodies against argatroban in patients who received multiple doses of argatroban.

Clinical efficacy and safety

Evidence of the efficacy of Argaron in HIT type II derives from data from two studies where a total of 568 adult patients were treated with Argaron. The average treatment duration employed in these clinical studies was 6 days with a maximum of 14 days. In the first prospective trial, an improvement in the composite outcome at 37 days (death, amputation, new thrombosis) was observed in the Argaron group versus the historical controls (n=46) The reduction of the incidence of the primary endpoint was consistent in the subgroups of patients having HIT type II without thromboembolic complications (25.6% vs 38.8%), p=0.014 by categorical analysis; p=0.007 by time-to-event analysis) and HIT type II with thromboembolic complications (43.8% vs 56.5%, p=0.131 by categorical analysis; p=0.018 by time-to event analysis).

The studies were not statistically powered for individual endpoints. However, in the first prospective study, the reduction of the incidence of individual endpoints for patients having HIT type II without and with thromboembolic complications respectively was as follows: mortality (16.9 vs 21.8%, n.s) and (18.1 vs 28.3%, n.s), amputation (1.9 vs 2.0%, n.s) and (11.1 vs 8.7%, n.s), new thromboses (6.9 vs 15%, p=0.027) and (14.6 vs 19.6%, n.s).

In the second follow-on study, similar outcomes were observed.

Paediatric population

The efficacy and safety of the use of Argaron in patients under 18 years of age has not been established. However, limited results from a prospective clinical study conducted in the USA in 18 seriously ill paediatric patients with (suspected) HIT Type II requiring an alternative to heparin anticoagulation are available.

The age range of the patients participating in this study were less than six months (8 patients), six months to less than 8 years (6 patients) and 8 to 16 years (4 patients). All patients had serious underlying conditions and were receiving multiple concomitant medications.

Thirteen patients received Argaron solely as a continuous infusion (no bolus dose). In the majority of these 13 patients dosing was initiated at 1 microgram/kg/min to achieve an aPTT of 1.5 to 3 times the baseline value (not exceeding 100 seconds). Most patients required multiple dose adjustments to maintain anticoagulation parameters within the desired range.

During the 30-day study period thrombotic events occurred during Argaron administration in two patients and following Argaron discontinuation in three other patients. Major bleeding occurred among two patients; one patient experienced an intracranial haemorrhage after 4 days of Argaron therapy in the setting of sepsis and thromobocytopenia. Another patient completed 14 days of treatment but experienced an intracranial haemorrhage while receiving Argaron following completion of the study treatment period.

As only limited data are available, an initial continuous infusion rate of 0.75 microgram/kg/min has been suggested in seriously ill paediatric patients with normal hepatic function. A reduced starting dose of 0.2 microgram/kg/min would be suggested in seriously ill paediatric patients with impaired hepatic function. The dose should be adjusted to achieve target aPTT 1.5-3 times the baseline value, not exceeding 100 seconds.

Absorption

Steady-state levels of both argatroban and anticoagulant effect are typically attained within 1-3 hours and are maintained until the infusion is discontinued or the dosage adjusted. Steady-state plasma argatroban concentrations increase proportionally with dose (for infusion doses up to 40 microgram/kg/min in healthy subjects) and are well correlated with steady-state anticoagulant effects. For infusion doses up to 40 microgram/kg/min, argatroban increases, in a dose-dependent fashion, the activated partial thromboplastin time (aPTT), the activated clotting time (ACT), the International Normalized Ratio (INR) and the thrombin time (TT) in healthy volunteers and cardiac patients.

Distribution

Argatroban distributes mainly in the extra-cellular fluid. The volume of distribution (Vdβ) was 391 ± 155 ml/kg (mean ± SD). Argatroban is 54% bound in human serum proteins, with binding to albumin and α₁-acid glycoprotein being 20% and 34% respectively.

Biotransformation

The metabolism of argatroban has not yet been fully characterized. The metabolites identified (M-1, M-2, and M-3) are formed by hydroxylation and aromatization of the 3-methyltetrahydroquinoline ring in the liver. The formation of the metabolites is catalysed in vitro by cytochrome P450 enzymes CYP3A4/5, but this is not a major path of elimination in vivo. The primary metabolite (M1) exerts 40-fold weaker antithrombin effect than argatroban. Metabolites M-1, M-2 and M-3 were detected in the urine, and M-1 was detected in plasma and faeces.

There is no interconversion of the 21-(R) and 21-(S) diastereoisomers. The ratio of diastereoisomers is unchanged by metabolism or hepatic impairment, remaining constant at 65:35 (±2%).

Elimination

On termination of the infusion, the concentration of argatroban decreased rapidly. The apparent terminal elimination half life (mean ± SD) is 52 ± 16 min. Clearance (mean ± SD) was 5.2 ± 1.3 ml/kg/min.

Argatroban is excreted mainly in the faeces, presumably through biliary secretion. Following intravenous infusion of ¹⁴C-radiolabelled argatroban 21.8 ± 5.8% of the dose was excreted in urine and 65.4 ± 7.1% in the faeces.

Special populations

Older people: clearance is approximately 15% lower then in younger persons. No age related dose adjustment is necessary.

Renal impairment: compared with patients with normal renal function (creatinine clearance > 80ml/min) who had a terminal half-life of 47±22 min, patients with severely impaired renal function (creatinine clearance ≤ 29ml/min) had only slight prolongation of this value (65±35 min). No initial dose regimen adjustment with respect to renal function is necessary.

Hepatic impairment: in patients with hepatic impairment (Child Pugh score 7 to 11) clearance was 26% of that of healthy volunteers. Initial dose reduction is required in patients with moderate hepatic impairment. Argaron is contraindicated in patients with severe hepatic impairment.

Paediatric patients: argatroban clearance is decreased in seriously ill paediatric patients. Based on population pharmacokinetic modelling, clearance in paediatric patients (0.17 L/hr/kg) was 50% lower compared to healthy adults (0.31 L/hr/kg). Population pharmacokinetic data also indicate that the infusion rate should be adjusted according to body weight.

Other special populations: Based on population pharmacokinetic modelling, patients with elevated bilirubin (secondary to cardiac complications or hepatic impairment) had, on average, 80% lower clearance (0.03 L/hr/kg) when compared to paediatric patients with normal bilirubin levels.

Preclinical data reveal no special hazard for humans based on conventional studies of safety pharmacology and genotoxicity. Toxicity studies with continuous intravenous infusions and reproduction toxicity studies using daily intravenous bolus injections achieved only limited systemic exposure to argatroban (2 times the exposure seen in humans). Although these studies do not suggest any particular risk to humans, their value is limited by the low systemic exposure realised.

This medicinal product must not be mixed with other medicinal products

Argaron 1 mg/ml Solution for Infusion is ready to use and requires no dilution before administration.

The drug product is unpreserved and intended for single use only. The solution should be used immediately after opening. Any unused solution should be discarded.

The solution should be inspected visually prior to use. Only clear solutions without visible particles should be used.

Light resisting measures such as foil protection for intravenous lines are not necessary. No significant potency losses have been noted following simulated delivery of the solution through intravenous tubing.

Any unused product or waste material should be disposed of in accordance with local requirements.