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Verbiage in bold below has been added to the noted sections:
4.5. Interactions with other Medicaments and other forms of Interaction
Phenylephrine may interact with cyclopropane and halothane and other halogenated inhalational anaesthetics, to induce ventricular fibrillation. An increased risk of arrhythmias may also occur if phenylephrine injection is given to patients receiving cardiac glycosides, quinidine or tricyclic antidepressants.
Phenylephrine may increase blood pressure and consequently reverse the action of many antihypertensive agents. Interactions of phenylephrine with alpha and beta receptor blocking drugs may be complex.
1Drugs which have an effect on α1 adrenoreceptors could potentiate (such as ganisetron) or inhibit (such as doxazosin or buspirone) the vasopressive action of phenylephrine.
4.8. Undesirable Effects
Extravasation of Phenylephrine Injection may cause tissue necrosis. Phenylephrine will cause a rise in blood pressure with headache and vomiting and this may produce cerebral haemorrhage and pulmonary oedema. There may also be a reflex bradycardia or tachycardia, other cardiac arrhythmias, anginal pain, palpitations and cardiac arrest, hypotension with dizziness, and fainting and flushing may occur. Phenylephrine may induce difficulty in micturition and urinary retention, 2mydriasis, dyspnoea, altered metabolism including disturbances of glucose metabolism, sweating, hypersalivation, transient tingling and coolness of the skin and temporary fullness of the head. Phenylephrine is without significant stimulating effects on the central nervous system at usual doses.
5.3. Preclinical Safety Data
3Phenylephrine has been used to induce cardiac myocyte hypertrophy in cultures of rat neonatal mycocytes at doses of 100 μM and 10 μM. To the best of our knowledge there have been no human studies associating therapeutic phenylephrine use with the development of cardiac myocyte hypertrophy.
10. Date of (Partial) Revision of the Text
May 2009
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