As part of a pilot study to assess the efficacy of propranolol in the
treatment of aggression in psychiatric patients, drug interactions of
propranolol with other agents were estimated by blood level monitoring. In
the two patients taking a standard oral dose of thioridazine, the addition
of propranolol caused a threefold and fivefold increase of plasma
thioridazine levels, which placed them in a potentially toxic range.
Although neither patient exhibited a toxic effect, these levels may be
associated with an increased risk of thioridazine-induced irreversible
pigmentary retinopathy, cardiac arrhythmias, and tardive dyskinesia. The
authors suggest precautionary monitoring of thioridazine plasma and other
relevant levels and clinical assessments when thioridazine and propranolol
are used in combination.Abstract Teaser