Mivacurium Disease Interactions

Parenteral medications formulated in multidose vials often contain benzyl alcohol as a preservative. Their use is considered by drug manufacturers to be contraindicated in neonates, particularly premature infants and infants of low birth weight. When used in bacteriostatic saline intravascular flush and endotracheal tube lavage solutions, benzyl alcohol has been associated with fatalities and severe respiratory and metabolic complications in low-birth-weight premature infants. Thus, single-dose formulations should always be used in infants whenever possible. However, many experts feel that, in the absence of benzyl alcohol-free equivalents, the amount of the preservative present in these formulations should not necessarily preclude their use if they are clearly indicated. The American Academy of Pediatrics considers benzyl alcohol in low doses (such as when used as a preservative in some medications) to be safe for newborns. However, the administration of high dosages of these medications must take into account the total amount of benzyl alcohol administered. The level at which toxicity may occur is unknown.

Patients with burns may develop resistance to non-depolarizing neuromuscular blocking agents. These patients may experience a shorter duration of action and/or require higher dosages of the drugs. The extent of altered response depends on the duration since and the size of the burn.

Some neuromuscular blocking agents stimulate the release of histamine, which can cause wheezing, bronchospasm, increased bronchial secretions, hypotension, tachycardia, and circulatory collapse. Hypotension may also occur due to ganglionic blockade or as a complication of positive pressure respiration. Tubocurarine appears to be the most potent inducer of histamine, followed by metocurine (no longer commercially available in the U.S.) and succinylcholine. Other agents with varying but lesser degrees of histamine-releasing properties include atracurium, mivacurium, and pancuronium (at excessive dosages). Therapy with these neuromuscular blocking agents should be administered cautiously in patients with clinically significant cardiovascular disease and/or a history of asthma or severe allergic reactions. Certain agents may prolong the QTc interval, especially during general anesthesia in pediatric patients. The initial dosage and rate of administration may need to be reduced, and hemodynamic and respiratory status carefully monitored. Neuromuscular blocking agents that appear to have little or no histamine-inducing effects include cisatracurium, doxacurium, pipecuronium, rocuronium, and vecuronium.

Neuromuscular blocking agents undergo metabolism by the liver. Elimination and effects may be prolonged in patients with liver disease. Therapy with neuromuscular blocking agents should be administered cautiously in patients with liver disease.

The use of neuromuscular blocking agents may cause prolonged respiratory paralysis. Therapy with neuromuscular blocking agents should be administered cautiously in patients with myasthenia gravis. Use of a peripheral nerve stimulator may be helpful in evaluating the level of neuromuscular blockade.

Patients with hemiparesis or paraparesis may require higher dosages of non-depolarizing neuromuscular blocking agents in the affected limbs. Neuromuscular monitoring should be performed on a non-paretic limb to avoid inaccurate dosing.

Neuromuscular blocking agents can cause respiratory depression and paralysis. Therapy with neuromuscular blocking agents should be administered cautiously in patients with pulmonary impairment. Treatment of respiratory paralysis consists of positive-pressure artificial respiration with oxygen and maintenance of a patent airway until the recovery of normal respiration is assured.

A few of the neuromuscular blocking agents, including doxacurium, mivacurium and pipecuronium, may have prolonged and/or enhanced effects in obese patients (i.e. weight >= 30% over ideal body weight for height). Dosing of these agents should be based on ideal body weight in obese patients.

Many of the non-depolarizing (competitive) neuromuscular blocking agents undergo significant elimination by the kidney. Their effects may, therefore, be prolonged in patients with renal dysfunction. Therapy with these neuromuscular blocking agents should be administered cautiously and initiated at reduced dosages in renally compromised patients, depending on the level of insufficiency. If possible, alternative agents should be considered. Atracurium, rocuronium and vecuronium do not depend on kidney function for clearance and are often the non-depolarizing muscle relaxants of choice in renal failure.