The lidocaine and phenylephrine topical solution may interfere with swallowing, and numbness of the tongue or buccal mucosa may increase the danger of biting trauma.
Local anaesthetics, (e.g. lidocaine) and sympathomimetics, (e.g. phenylephrine) may produce systemic adverse effects as a result of the raised plasma concentrations which ensue when the rate of absorption into the circulation exceeds the rate of breakdown, for example, by absorption of large amounts through mucous membranes or damaged skin or from highly vascular areas.
Possible Systemic Effects due to Lidocaine
The systemic toxicity of local anaesthetics mainly involves the central nervous system and the cardiovascular system. Excitation of the CNS may be manifested by restlessness, excitement, nervousness, dizziness, tinnitus, blurred vision, nausea and vomiting, muscle twitching and tremors, and convulsions. Numbness of the tongue and perioral region may appear as an early sign of systemic toxicity. Excitation may be transient and followed by depression with drowsiness, respiratory failure and coma. There may be simultaneous effects on the cardiovascular system with myocardial depression and peripheral vasodilatation resulting in hypotension and bradycardia; arrhythmias and cardiac arrest may occur.
Some local anaesthetics cause methaemoglobinaemia.
Possible Systemic Effects due to Phenylephrine.
Sympathomimetics may produce a wide range of adverse effects, most of which mimic the results of excessive stimulation of the sympathetic nervous system. These effects are mediated via the various types of adrenergic receptor, and the adverse effects of an individual drug depend to some extent upon its relative agonist activity on these different types of receptor at a given dose.
Central effects of sympathomimetic agents include fear, anxiety, nervousness, restlessness, tremors, insomnia, confusion, irritability, psychotic states and epileptiform convulsions. Appetite may be reduced and nausea and vomiting may occur.
Effects on the cardiovascular system are complex. Stimulation of alpha-adrenergic receptors produced vasoconstriction with resultant hypertension. This vasoconstriction is sometimes sufficiently severe to produce gangrene when sympathomimetics are infiltrated into the digits. The rise of blood pressure may produce cerebral haemorrhage and pulmonary oedema. There may also be a reflex bradycardia, but stimulation of β1-adrenergic receptors of the heart may produce tachycardia and cardiac arrhythmias, anginal pain, palpitations, and cardiac arrest: hypotension with dizziness and fainting, and flushing, may occur. An increased incidence of sudden death, sometimes attributed to the induction of ventricular arrhythmias, has been associated with the excessive use of sympathomimetic agents in aerosol form; although the association has been questioned by some authorities, it is important to avoid excessive doses.
Other effects that may occur with sympathomimetic agents include difficulty in micturition, particularly in the case of prostatic hypertrophy, and urinary retention, dyspnoea, weakness, altered metabolism, sweating, hyperpyrexia and hypersalivation. Headache is also common.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme: Website: www.mhra.gov.uk/yellowcard.