Drug Interactions between brimonidine / dorzolamide / latanoprost / timolol ophthalmic and iopamidol

MONITOR: Limited data suggest that patients receiving beta-blockers may have an increased risk of severe hypotensive and/or hypersensitivity reactions to parenteral iodinated contrast media. In addition, allergic/anaphylactoid reactions in these patients may be more difficult to treat. The mechanism is unknown. Theoretically, beta-blocker ophthalmic solutions may also interact, as they are systemically absorbed and can produce clinically significant systemic effects even at low or undetectable plasma levels.

MANAGEMENT: Patients who have received beta-blockers should be closely monitored for adverse reactions to iodinated contrast media. If anaphylaxis occurs, clinicians should be aware that beta-blockers may attenuate the response to epinephrine. Thus, larger doses of epinephrine may be necessary to overcome the bronchospasm, although such large doses can also cause excessive alpha-adrenergic stimulation resulting in hypertension, reflex bradycardia, heart block, and possible potentiation of bronchospasm. Alternative treatments recommended include vigorous supportive care (e.g., fluids) and the use of parenteral beta-agonists for bronchospasm and norepinephrine for hypotension.

MONITOR: Topically administered alpha-2 adrenergic receptor agonists such as apraclonidine and brimonidine are systemically absorbed, with the potential for producing rare but clinically significant systemic effects such as hypotension and bradycardia. The possibility for an additive or potentiating effect on blood pressure and heart rate should be considered when used with other medications that affect these parameters, such as ophthalmic and systemic beta blockers, vasodilators, cardiac glycosides, and antihypertensive agents.

MANAGEMENT: Blood pressure and pulse rate should be monitored regularly when topical alpha-2 adrenergic receptor agonists are prescribed in combination with cardiovascular drugs. Patients should be advised to notify their physician if they experience slow pulse, irregular heartbeat, dizziness, lightheadedness, or syncope.