| Treatment with Refludan should be initiated under the guidance of a physician with experience in coagulation disorders. Initial dosage Anticoagulation in adult patients with HIT type II and thromboembolic disease: 0.4 mg / kg body weight intravenously as a bolus dose followed by 0.15 mg / kg body weight / hour as a continuous intravenous infusion for 2 - 10 days or longer if clinically needed.Normally, the dosage depends on the patient's body weight. This is valid up to a body weight of 110 kg. In patients with a body weight exceeding 110 kg the dosage should not be increased beyond the 110 kg body weight dose (see also tables 2 and 3, below).Monitoring and modification of the Refludan dosage regimen Standard recommendations Monitoring: In general, the dosage (infusion rate) should be adjusted to the activated partial thromboplastin time, aPTT. The first aPTT determination should be done 4 hours after start of Refludan therapy. The aPTT should be monitored at least once daily. More frequent determinations may be necessary, for example, in patients with renal impairment or with an increased risk of bleeding. Target range (therapeutic window) for the aPTT:
- Using "Actin FS" or "Neothromtin" on automated coagulometers the target range for the aPTT is 1.5 fold to 3 fold prolongation of the normal control value.
- With other reagents, the upper limit of the therapeutic aPTT window should be reduced to 2.5 fold prolongation of the normal control value.
- To obtain specific and exact aPTT limits, the laboratory equipment / test reagent used may be calibrated by spiking standardised human plasma with 0.15 μg/ml lepirudin (lower limit) and 1.5 μg/ml lepirudin (upper limit).Dose modifications: Any aPTT value out of the target range is to be confirmed at once before drawing conclusions with respect to dose modifications, unless there is a clinical need to react immediately. If the confirmed aPTT value is above the target range, the infusion should be stopped for two hours. At restart, the infusion speed should be decreased by 50 % (no additional intravenous bolus should be administered). The aPTT should be determined again 4 hours later. If the confirmed aPTT value is below the target range, the infusion speed should be increased by 20 %. The aPTT should be determined again 4 hours later. In general, an infusion rate of 0.21 mg/kg/hour should not be exceeded without checking for coagulation abnormalities which might be preventing an appropriate aPTT response.Recommendations for use in patients scheduled for a switch to oral anticoagulation If a patient is scheduled to receive coumarin derivatives (vitamin K antagonists) for oral anticoagulation after Refludan therapy, the following should apply: Coumarin derivatives should be initiated only when platelet counts are normalising. The intended maintenance dose should be started with no loading dose. To avoid prothrombotic effects when initiating coumarin, continue parenteral anticoagulation for 4 to 5 days (see oral anticoagulant package insert for information). The parenteral agent can be discontinued when the International Normalised Ratio (INR) stabilises within the desired target range.Recommendations for use in patients with renal impairment As lepirudin is almost exclusively excreted and metabolised renally (see also section 5.2), the patient's renal function should be considered prior to administration. In case of renal impairment relative overdose might occur even under standard dosage regimen. Therefore, the bolus dose and infusion rate must be reduced in case of known or suspected renal insufficiency (creatinine clearance below 60 ml/min or creatinine value above 15 mg/l [133 μmol/l]).In clinical trials, Refludan was not therapeutically administered to HIT type II patients with significant renal impairment. The following dosage recommendations are based on single-dose studies in a small number of patients with renal impairment. Therefore, these recommendations are only tentative.Whenever available, dose adjustments should be based on creatinine clearance values as obtained from a reliable method (24 h urine sampling). In all other cases the dose adjustment is based on the creatinine value.In any case, the bolus dose must be reduced to 0.2 mg / kg body weight.The infusion rate must be reduced according to table 1. Additional aPTT monitoring is mandatory.Table 1: Reduction of infusion rate in patients with renal impairmentCreatinine clearance [ml/min] | Creatinine value [mg/l (μmol/l)] | Adjusted infusion rate [% of original dose] | 45 60 | 16 20 (141 - 177) | 50 % | 30 44 | 21 30 (178 - 265) | 30 % | 15 29 | 31 - 60 (266 - 530) | 15 % | below 15* | above 60 (530)* | avoid or STOP infusion !* | * In haemodialysis patients or in case of acute renal failure (creatinine clearance below 15 ml/min or creatinine value above 60 mg/l [530 μmol/l]), infusion of Refludan is to be avoided or stopped. Only if aPTT values have fallen below the lower therapeutic limit (see Monitoring: target range), further intravenous bolus doses of 0.1 mg / kg body weight may be considered every other day.Method of administration Reconstitute the lyophilisate as described in section 6.6.Initial intravenous bolus: For intravenous bolus injection, a solution with a concentration of 5 mg/ml is needed.Intravenous injection is to be carried out slowly.Table 2: Examples for standard injection volume according to body weightBody weight | Injection volume
[ml] | [kg] | Dosage 0.4
mg / kg body weight | Dosage 0.2
mg / kg body weight | 50 | 4.0 | 2.0 | 60 | 4.8 | 2.4 | 70 | 5.6 | 2.8 | 80 | 6.4 | 3.2 | 90 | 7.2 | 3.6 | 100 | 8.0 | 4.0 | 110
| 8.8 | 4.4 |
Intravenous infusion: For continuous intravenous infusion, a solution with a concentration of 2 mg/ml is needed.The speed of the perfusor automate [ml per hour] is to be set in a body weight dependent fashion.Table 3: Examples for standard infusion speed according to body weightBody weight | Infusion speed
[ml/h] | [kg] | Dosage 0.15
mg / kg body weight / h | Dosage 0.1
mg / kg body weight / h | 50 | 3.8 | 2.5 | 60 | 4.5 | 3.0 | 70 | 5.3 | 3.5 | 80 | 6.0 | 4.0 | 90 | 6.8 | 4.5 | 100 | 7.5 | 5.0 | 110
| 8.3 | 5.5 |
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