<p>Prolonged recovery time with barbiturates or narcotics. May potentiate neuromuscular blocking effects of atracurium and tubocurarine including resp depression with apnoea. May increase risk of bradycardia, hypotension or decreased cardiac output with halogenated anaesthetics. May potentiate CNS depression and risk of resp depression with CNS depressants (e.g. phenothiazines, sedating H1-blockers, skeletal muscle relaxants). May antagonise hypnotic effect of thiopental. May increase risk of HTN with thyroid hormones. May increase risk of hypotension with antihypertensive agents. Reduction in seizure threshold resulting in unpredictable extensor-type seizures when given concurrently with theophylline.</p>