Toloxatone Phenylephrine

Like moclobemide, toloxatone, a selective and reversible inhibitor of monoamine oxidase type A, is thought to be relatively safe in combination with sympathomimetics (SEDA-18, 16). However, sweating, tachycardia, and headache have been reported when terbutaline was added to toloxatone and phenylephrine (SEDA-18, 16). In healthy volunteers, doses up to 600 mg/day did not produce hypertensive reactions on challenge with oral tyramine (SEDA-17, 17). Two fatal cases of fulminant hepatitis have been reported (SEDA-16, 7). 

An isolated case of tachycardia and apprehension has been described in an asthmatic taking phenelzine after salbutamol (albuterol) was added. Hypomania was seen in another asthmatic taking phenelzine when inhaled isoetarine was added. Hypertensive crisis occurred in a woman taking toloxatone and phenylephrine when given [oral] terbutaline. 

A 72-year old woman taking long-term levothyroxine, toloxatone 400 mg daily (for 2 months), and phenylephrine (for 3 weeks) developed episodes of hypertension, sweating, tachycardia, and headache within 3 days after starting [oral] terbutaline 10 mg daily. She had extremely high plasma catecholamine levels. All drugs were stopped on admission to hospital and she recovered over 2 to 3 days. ... 

Note that drugs with directly-acting sympathomimetic effects (of which beta agonists are an example) do not normally interact to cause hypertension with MAOIs, see sympathomimetics directly-acting , (below). However, phenylephrine (which has some indirect actions, see sympathomimetics phenylephrine , (p.l 148)) may have contributed to the reaction between toloxatone and terbutaline, and the fact that terbutaline seems to have been given orally would also have eontributed. The hypomania reaction is not understood. 

Lefebvre H, Richard R, Noblet C, Moore N, Wolf L-M. Life-threatening pseudo-phaeochro-mocytoma after toloxatone, terbutaline, and phenylephrine. Lancet 1993) 341, 555-6. 

A case of life-threatening hypertension occurred in a patient taking toloxatone, non-prescription phenylephrine and terbutaline , (p.ll46). 

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See also in sourсe #XX -- [ ]

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