The dosage information provided below is intended as a guide only. Doses of MIVACRON should be individualized (see CLINICAL PHARMACOLOGY — Individualization of Dosages). Factors that may warrant dosage adjustment include but may not be limited to: the presence of significant kidney, liver, or cardiovascular disease, obesity (patients weighing greater than or equal to 30% more than ideal body weight for height), asthma, reduction in plasma cholinesterase activity, and the presence of inhalational anesthetic agents.
When using MIVACRON or other neuromuscular blocking agents to facilitate tracheal intubation, it is important to recognize that the most important factors affecting intubation are the depth of general anesthesia and the level of neuromuscular block. Satisfactory intubating conditions can usually be achieved before complete neuromuscular block is attained if there is adequate anesthesia.
The use of a peripheral nerve stimulator will permit the most advantageous use of MIVACRON, minimize the possibility of overdosage or underdosage, and assist in the evaluation of recovery. When using a stimulator to monitor onset of neuromuscular block, clinical studies have shown that all four twitches of the train-of-four response may be present, with little or no fade, at the times recommended for intubation. Therefore, as with other neuromuscular blocking agents, it is important to use other criteria, such as clinical evaluation of the status of relaxation of jaw muscles and vocal cords, in conjunction with peripheral muscle twitch monitoring, to guide the appropriate time of intubation.
Doses of 0.15 mg/kg administered over 5 to 15 seconds, 0.2 mg/kg administered over 30 seconds, or 0.25 mg/kg administered in divided doses (0.15 mg/kg followed in 30 seconds by 0.1 mg/kg) are recommended for facilitation of tracheal intubation for most patients (see Table 7).
|Dosing Paradigm*||Anesthetic Induction Technique Studied||Time to Generally Good-to- Excellent Intubating Conditions|
|0.15 mg/kg, intravenous (over 5 to 15 sec)||Thiopental/opioid/N2 O/O2 or propofol/opioid||2.5 to 3 min after completion of dose|
|0.2 mg/kg, intravenous (over 30 sec)||Thiopental/opioid/N2 O/O2 or propofol/opioid||2 to 2.5 min after completion of dose|
|0.25 mg/kg, intravenous (0.15 mg/kg followed in 30 sec by 0.1 mg/kg)||Propofol/opioid||1.5 to 2 min after completion of 0.15 mg/kg dose|
|* Dosing instituted after induction of adequate general anesthesia.|
The purpose of slowed or divided dosing of MIVACRON at doses above 0.15 mg/kg is to minimize the transient decreases in blood pressure observed in some patients given these doses over 5 to 15 seconds (see CLINICAL PHARMACOLOGY, PRECAUTIONS, and ADVERSE REACTIONS). The quality of intubation conditions does not significantly differ for the times and doses of MIVACRON recommended in Table 7, but the onset of suitable intubation conditions may be reached earlier with higher doses. The choice of a particular dose and regimen should be based on individual circumstances and patient requirements (see CLINICAL PHARMACOLOGY — Individualization of Dosages).
In patients with clinically significant cardiovascular disease and in patients with any history suggesting a greater sensitivity to the release of histamine or other mediators (e.g., asthma), the dose of MIVACRON should be 0.15 mg/kg or less, administered over 60 seconds (see PRECAUTIONS). No data are available on the use of doses of MIVACRON above 0.15 mg/kg in patients with clinically significant kidney or liver disease.
Clinically effective neuromuscular block may be expected to last for 15 to 20 minutes (range: 9 to 38 minutes) and spontaneous recovery may be expected to be 95% complete in 25 to 30 minutes (range: 16 to 41 minutes) following 0.15 mg/kg MIVACRON administered to patients receiving opioid/nitrous oxide/oxygen anesthesia. The expected duration of clinically effective block and time to 95% spontaneous recovery following 0.2 mg/kg MIVACRON are approximately 20 and 30 minutes, respectively, and following 0.25 mg/kg MIVACRON are approximately 25 and 35 minutes. Initiation of maintenance dosing during opioid/nitrous oxide/oxygen anesthesia is generally required approximately 15, 20 and 25 minutes following initial doses of 0.15 mg/kg, 0.2 mg/kg, and 0.25 mg/kg MIVACRON, respectively (see Table 1). Maintenance doses of 0.1 mg/kg each provide approximately 15 minutes of additional clinically effective block. For shorter or longer durations of action, smaller or larger maintenance doses may be administered.
The neuromuscular blocking action of MIVACRON is potentiated by isoflurane or enflurane anesthesia. Recommended initial doses of MIVACRON may be used to facilitate tracheal intubation prior to the administration of these agents; however, if MIVACRON is first administered after establishment of stable-state isoflurane or enflurane anesthesia (administered with nitrous oxide/oxygen to achieve 1.25 MAC), the initial dose of MIVACRON may be reduced by as much as 25%. Greater reductions in the dose of MIVACRON may be required with higher concentrations of enflurane or isoflurane. With halothane, which has only a minimal potentiating effect on MIVACRON, a smaller dosage reduction may be considered.
Continuous infusion of MIVACRON may be used to maintain neuromuscular block. Upon early evidence of spontaneous recovery from an initial dose, an initial infusion rate of 9 to 10 mcg/kg/min is recommended. If continuous infusion is initiated simultaneously with the administration of an initial dose, a lower initial infusion rate should be used (e.g., 4 mcg/kg/min). In either case, the initial infusion rate should be adjusted according to the response to peripheral nerve stimulation and to clinical criteria. On average, an infusion rate of 5 to 7 mcg/kg/min (range: 1 to 15 mcg/kg/min) may be expected to maintain neuromuscular block within the range of 89% to 99% for extended periods in adults receiving opioid/nitrous oxide/oxygen anesthesia. In some patients, particularly those with higher infusion requirements (greater than 8 mcg/kg/min) during the first 30 minutes, the infusion rate required to maintain 89% to 99% T1 suppression may decrease gradually (by greater than or equal to 30%) with time over a 4- to 6-hour period of infusion (see CLINICAL PHARMACOLOGY — Pharmacodynamics). Reduction of the infusion rate by up to 35% to 40% should be considered when MIVACRON is administered during stable-state conditions of isoflurane or enflurane anesthesia (administered with nitrous oxide/oxygen to achieve 1.25 MAC). Greater reductions in the infusion rate of MIVACRON may be required with greater concentrations of enflurane or isoflurane. With halothane, smaller reductions in infusion rate may be required.
Dosage requirements for MIVACRON on a mg/kg basis are higher in children than in adults. Onset and recovery of neuromuscular block occur more rapidly in children than in adults (see CLINICAL PHARMACOLOGY).
The recommended dose of MIVACRON for facilitating tracheal intubation in children 2 to 12 years of age is 0.2 mg/kg administered over 5 to 15 seconds. When administered during stable opioid/nitrous oxide/oxygen anesthesia, 0.2 mg/kg of MIVACRON produces maximum neuromuscular block in an average of 1.9 minutes (range: 1.3 to 3.3 minutes) and clinically effective block for 10 minutes (range: 6 to 15 minutes). Maintenance doses are generally required more frequently in children than in adults. Administration of doses of MIVACRON above the recommended range (greater than 0.2 mg/kg) is associated with transient decreases in MAP in some children (see CLINICAL PHARMACOLOGY — Hemodynamics). MIVACRON has not been studied in pediatric patients below the age of 2 years.
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