Loading bolus

Reduce loading (bolus) doses - Reduce loading (bolus) doses in patients with congestive heart failure (CHF) or reduced cardiac output and in the elderly. However, some investigators recommend the usual loading dose be administered and only the maintenance dosage be reduced. 

FIGURE 7.12 Infusion with various loading bolus Cp° values... 

In a retrospective analysis of 36 patients who received intravenous levetiracetam for refractory status epilepticus [209 ] a median dose of 3000 mg/day (range 1000-9000) was used as a loading bolus or by continuous pump infusion. Status epilepticus was terminated in 69% of patients. None had cardiac dysrhythmias or significantly reduced blood pressure, or required an increase in the dose of catecholamines. Two patients had nausea and vomiting during levetiracetam loading, leading to aspiration pneumonia in one. 

Indications for treatment with streptokinase include acute occlusion of arteries, deep vein thrombosis, and pulmonary embolism. Streptokinase therapy in coronary thrombosis, which is the usual cause of myocardial infarction (54,71,72), has proved to be valuable. In this frequently fatal condition, the enzyme is adrninistered intravenously at a dose of 1.5 million units over 60 min, or given by intracoronary infusion at a 20,000- to 50,000-unit bolus dose followed by 2000 to 4000 units/min for 60 min therapy must be instituted as soon as practicable after the diagnosis of heart attack is made. For deep vein thrombosis, pulmonary embolism, or arterial occlusion, streptokinase is infused at a loading dose of 250,000 units given over 30 min, followed by a maintenance dose of 100,000 units over a 60-min period. 

Compared to streptokinase, urokinase has been less extensively studied because of its high cost, ie, about 10 times that of a comparable treatment with streptokinase. In addition to the indications described for streptokinase, urokinase is indicated for use in patients with prior streptokinase treatment, or prior Streptococcal infection. Urokinase is commonly used at a loading dose of 4400 units /kg, with a maintenance intravenous infusion dose of 4400 units/kg/h for thromboses other than acute myocardial infarction. In the latter case, a much larger dose, ie, 0.5—2.0 million units/h or a bolus dose of 1.0 million units followed by a 60-min infusion with 1.0 million units, has been found optimal (106). An intracoronary dose of 2000 units/min for two hours was used in one comparative study with intracoronary streptokinase (107). In this study, urokinase exhibited efficacy equivalent to streptokinase with fewer side effects. Other studies with intracoronary urokinase have adrninistered doses ranging from 2,000 to 24,000 units/min with a reperfusion efficacy of 60—89% (108—112). In another urokinase trial, 2.0 million units were adrninistered intravenously, resulting in a thrombolytic efficacy of 60% (113). Effectiveness in terms of reduction in mortaUty rate has not been deterrnined because of the small number of patients studied. 

A loading dose of 0.2 mg/kg (repeated up to a maximum of 2 mg/kg) followed by a continuous infusion of 0.05 to 2 mg/kg per hour is recommended in RSE.29-31 The dose must be adjusted during prolonged infusions, especially in patients with renal impairment, as the active metabolite can accumulate.32 Breakthrough seizures are common with midazolam infusions and usually respond to a bolus and a 20% increase in the rate. Despite this, tachyphylaxis can occur and the patient should be switched to another agent if seizure activity continues. 

Equipotent doses of loop diuretics (furosemide, bumetanide, torsemide, ethacrynic acid) have similar efficacy. Ethacrynic acid is reserved for sulfa-allergic patients. Continuous infusions of loop diuretics appear to be more effective and to have fewer adverse effects than intermittent boluses. An initial IV loading dose (equivalent to furosemide 40 to 80 mg) should be administered before starting a continuous infusion (equivalent to furosemide 10 to 20 mg/hour). 

The maximum advisable dosage to be given either by repeated bolus injections or such loading infusion is 1 g. 

Short-term management of intractable heart failure IV Infusion (Continuous) Initially, 0.75 mg/kg loading dose over 2-3 minutes followed by a maintenance infusion of Sand 10 mcg/kg/min. A bolus dose of 0.75 mg/kg may be given 30 minutes after the initiation of therapy. Use within 24 hours and do not dilute with solutions that contain dextrose. Maximum lOmg/kg/day... 

Patient-controlled analgesia (PCA) IV Loading dose 50-100 mg. Intermittent bolus 5-30 mg. Lockout interval 10-20 min. Continuous infusion 5 0mg/hr. Maximum (4-hr) 200-300 mg. 

Aprotinin is not effective after oral administration, but is administered intravenously as a loading dose followed by a continuous infusion. Its activity is expressed as kallikrein inactivation units (KIU). The conventional (Munich) dose regimen consists of an initial 2 x 10 KIU bolus, a similar initial dose to prime the bypass machine, and then 0.5 x 10 KIU/ hour by continuous infusion thereafter. The half-life of aprotinin is about 2 hours. Plasma concentrations of 125 KlU/ml are necessary to inhibit plasmin, but a... 

---