Drug Interactions between chlorpheniramine / guaifenesin / phenylephrine and timolol ophthalmic

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

MONITOR: Coadministration of two or more sympathomimetic agents may increase the risk of adverse effects such as nervousness, irritability, and increased heart rate. Central nervous system (CNS) stimulants, particularly amphetamines, can potentiate the adrenergic response to vasopressors and other sympathomimetic agents. Additive increases in blood pressure and heart rate may occur due to enhanced peripheral sympathetic activity.

MANAGEMENT: Caution is advised if two or more sympathomimetic agents are coadministered. Pulse and blood pressure should be closely monitored.

Topically applied beta-adrenergic receptor blocking agents (aka beta-blockers) are systemically absorbed, with the potential for producing clinically significant systemic effects even at low or undetectable plasma levels. The use of beta-blockers in patients with a history of allergic reactions or anaphylaxis may be associated with heightened reactivity to culprit allergens. The frequency and/or severity of attacks may be increased during beta-blocker therapy. In addition, these patients may be refractory to the usual doses of epinephrine used to treat acute hypersensitivity reactions and may require a beta-agonist such as isoproterenol.

Ophthalmic beta-adrenergic receptor blocking agents (aka beta-blockers) in general should not be used in patients with a current or past history of bronchial asthma or chronic obstructive pulmonary disease. Topically applied beta-blockers are systemically absorbed, with the potential for producing clinically significant systemic effects even at low or undetectable plasma levels. In the respiratory tract, beta blockade may adversely affect pulmonary function by counteracting the bronchodilation produced by catecholamine stimulation of beta-2 receptors. Although agents with beta-1 selectivity (e.g., betaxolol) are considered safer in patients with bronchospastic diseases, cardioselectivity is not absolute and may be lost with larger doses or higher plasma levels.

The use of ophthalmic beta-adrenergic receptor blocking agents (aka beta-blockers) is considered by manufacturers to be contraindicated in patients with cardiogenic shock. Topically applied beta-blockers are systemically absorbed, with the potential for producing clinically significant systemic effects even at low or undetectable plasma levels. In cardiac tissues, beta blockade causes a reduction in inotropic as well as chronotropic activity, which may further depress cardiac output and blood pressure in such patients.

Sympathomimetic agents may cause adverse cardiovascular effects, particularly when used in high dosages and/or in susceptible patients. In cardiac tissues, these agents may produce positive chronotropic and inotropic effects via stimulation of beta- 1 adrenergic receptors. Cardiac output, oxygen consumption, and the work of the heart may be increased. In the peripheral vasculature, vasoconstriction may occur via stimulation of alpha-1 adrenergic receptors. Palpitations, tachycardia, arrhythmia, hypertension, reflex bradycardia, coronary occlusion, cerebral vasculitis, myocardial infarction, cardiac arrest, and death have been reported. Some of these agents, particularly ephedra alkaloids (ephedrine, ma huang, phenylpropanolamine), may also predispose patients to hemorrhagic and ischemic stroke. Therapy with sympathomimetic agents should generally be avoided or administered cautiously in patients with sensitivity to sympathomimetic amines, hyperthyroidism, or underlying cardiovascular or cerebrovascular disorders. These agents should not be used in patients with severe coronary artery disease or severe/uncontrolled hypertension.

Due to their negative inotropic and chronotropic effects on the heart, beta-adrenergic receptor blocking agents (aka beta-blockers) reduce cardiac output and may precipitate or aggravate symptoms of arterial insufficiency in patients with peripheral vascular disease. In addition, the nonselective beta-blockers (e.g., timolol, carteolol) may attenuate catecholamine-mediated vasodilation during exercise by blocking beta-2 receptors in peripheral vessels. Since topically applied beta-blockers are systemically absorbed and may produce clinically significant systemic effects even at low or undetectable plasma levels, therapy with ophthalmic beta-blockers should be administered cautiously in patients with peripheral vascular disease. Close monitoring for progression of arterial obstruction is advised.

Sympathomimetic agents may cause adverse cardiovascular effects, particularly when used in high dosages and/or in susceptible patients. In cardiac tissues, these agents may produce positive chronotropic and inotropic effects via stimulation of beta- 1 adrenergic receptors. Cardiac output, oxygen consumption, and the work of the heart may be increased. In the peripheral vasculature, vasoconstriction may occur via stimulation of alpha-1 adrenergic receptors. Palpitations, tachycardia, arrhythmia, hypertension, reflex bradycardia, coronary occlusion, cerebral vasculitis, myocardial infarction, cardiac arrest, and death have been reported. Some of these agents, particularly ephedra alkaloids (ephedrine, ma huang, phenylpropanolamine), may also predispose patients to hemorrhagic and ischemic stroke. Therapy with sympathomimetic agents should generally be avoided or administered cautiously in patients with sensitivity to sympathomimetic amines, hyperthyroidism, or underlying cardiovascular or cerebrovascular disorders. These agents should not be used in patients with severe coronary artery disease or severe/uncontrolled hypertension.

Ophthalmic beta-adrenergic receptor blocking agents (aka beta-blockers) in general should not be used in patients with a current or past history of bronchial asthma or chronic obstructive pulmonary disease. Topically applied beta-blockers are systemically absorbed, with the potential for producing clinically significant systemic effects even at low or undetectable plasma levels. In the respiratory tract, beta blockade may adversely affect pulmonary function by counteracting the bronchodilation produced by catecholamine stimulation of beta-2 receptors. Although agents with beta-1 selectivity (e.g., betaxolol) are considered safer in patients with bronchospastic diseases, cardioselectivity is not absolute and may be lost with larger doses or higher plasma levels.

The use of ophthalmic beta-adrenergic receptor blocking agents (aka beta-blockers) is considered by manufacturers to be contraindicated in patients with overt congestive heart failure (CHF). Topically applied beta-blockers are systemically absorbed, with the potential for producing clinically significant systemic effects even at low or undetectable plasma levels. Since sympathetic stimulation may be important in maintaining the hemodynamic function in patients with CHF, beta blockade can worsen the heart failure. However, therapy with ophthalmic beta-blockers can be administered cautiously in some CHF patients provided they are well compensated and receiving digitalis, diuretics, an ACE inhibitor, and/or nitrates. Beta-blockers should be discontinued if cardiac failure develops or worsens during therapy.

Beta-adrenergic receptor blocking agents (aka beta-blockers) may mask symptoms of hypoglycemia such as tremors, tachycardia and blood pressure changes. In addition, the nonselective beta-blockers (e.g., timolol, carteolol) may inhibit catecholamine-mediated glycogenolysis, thereby potentiating insulin-induced hypoglycemia and delaying the recovery of normal blood glucose levels. Since topically applied beta-blockers are systemically absorbed and may produce clinically significant systemic effects even at low or undetectable plasma levels, therapy with ophthalmic beta-blockers should be administered cautiously in patients with diabetes or predisposed to spontaneous hypoglycemia.

The use of ophthalmic beta-adrenergic receptor blocking agents (aka beta-blockers) is considered by manufacturers to be contraindicated in patients with sinus bradyarrhythmia or heart block greater than the first degree (unless a functioning pacemaker is present). Topically applied beta-blockers are systemically absorbed, with the potential for producing clinically significant systemic effects even at low or undetectable plasma levels. In cardiac tissues, beta blockade causes a reduction in inotropic as well as chronotropic activity, which may further depress cardiac function in such patients.

Sympathomimetic agents may cause adverse cardiovascular effects, particularly when used in high dosages and/or in susceptible patients. In cardiac tissues, these agents may produce positive chronotropic and inotropic effects via stimulation of beta- 1 adrenergic receptors. Cardiac output, oxygen consumption, and the work of the heart may be increased. In the peripheral vasculature, vasoconstriction may occur via stimulation of alpha-1 adrenergic receptors. Palpitations, tachycardia, arrhythmia, hypertension, reflex bradycardia, coronary occlusion, cerebral vasculitis, myocardial infarction, cardiac arrest, and death have been reported. Some of these agents, particularly ephedra alkaloids (ephedrine, ma huang, phenylpropanolamine), may also predispose patients to hemorrhagic and ischemic stroke. Therapy with sympathomimetic agents should generally be avoided or administered cautiously in patients with sensitivity to sympathomimetic amines, hyperthyroidism, or underlying cardiovascular or cerebrovascular disorders. These agents should not be used in patients with severe coronary artery disease or severe/uncontrolled hypertension.

Beta-adrenergic receptor blocking agents (aka beta-blockers) may mask some symptoms of hyperthyroidism such as tachycardia, anxiety, tremor, and heat intolerance. Abrupt withdrawal of beta-blocker therapy in thyrotoxic patients may exacerbate symptoms of hyperthyroidism or precipitate a thyroid storm. Since topically applied beta-blockers are systemically absorbed and may produce clinically significant systemic effects even at low or undetectable plasma levels, therapy with ophthalmic beta-blockers should be administered cautiously in patients with or suspected of having hyperthyroidism. Cessation of beta-blocker therapy, when necessary, should occur gradually over a period of 1 to 2 weeks. Patients should be advised not to discontinue treatment without first consulting with the physician. Close monitoring is recommended during and after therapy withdrawal.

Due to their negative inotropic and chronotropic effects on the heart, beta-adrenergic receptor blocking agents (aka beta-blockers) reduce cardiac output and may precipitate or aggravate symptoms of arterial insufficiency in patients with peripheral vascular disease. In addition, the nonselective beta-blockers (e.g., timolol, carteolol) may attenuate catecholamine-mediated vasodilation during exercise by blocking beta-2 receptors in peripheral vessels. Since topically applied beta-blockers are systemically absorbed and may produce clinically significant systemic effects even at low or undetectable plasma levels, therapy with ophthalmic beta-blockers should be administered cautiously in patients with peripheral vascular disease. Close monitoring for progression of arterial obstruction is advised.

Sympathomimetic agents may cause adverse cardiovascular effects, particularly when used in high dosages and/or in susceptible patients. In cardiac tissues, these agents may produce positive chronotropic and inotropic effects via stimulation of beta- 1 adrenergic receptors. Cardiac output, oxygen consumption, and the work of the heart may be increased. In the peripheral vasculature, vasoconstriction may occur via stimulation of alpha-1 adrenergic receptors. Palpitations, tachycardia, arrhythmia, hypertension, reflex bradycardia, coronary occlusion, cerebral vasculitis, myocardial infarction, cardiac arrest, and death have been reported. Some of these agents, particularly ephedra alkaloids (ephedrine, ma huang, phenylpropanolamine), may also predispose patients to hemorrhagic and ischemic stroke. Therapy with sympathomimetic agents should generally be avoided or administered cautiously in patients with sensitivity to sympathomimetic amines, hyperthyroidism, or underlying cardiovascular or cerebrovascular disorders. These agents should not be used in patients with severe coronary artery disease or severe/uncontrolled hypertension.

The use of ophthalmic beta-adrenergic receptor blocking agents (aka beta-blockers) is considered by manufacturers to be contraindicated in patients with sinus bradyarrhythmia or heart block greater than the first degree (unless a functioning pacemaker is present). Topically applied beta-blockers are systemically absorbed, with the potential for producing clinically significant systemic effects even at low or undetectable plasma levels. In cardiac tissues, beta blockade causes a reduction in inotropic as well as chronotropic activity, which may further depress cardiac function in such patients.

It has been suggested that the anticholinergic effect of antihistamines may reduce the volume and cause thickening of bronchial secretions, resulting in obstruction of respiratory tract. Some manufacturers and clinicians recommend that therapy with antihistamines be administered cautiously in patients with asthma or chronic obstructive pulmonary disease.

Sympathomimetic agents may cause or worsen urinary difficulty in patients with prostate enlargement due to smooth muscle contraction in the bladder neck via stimulation of alpha-1 adrenergic receptors. Therapy with sympathomimetic agents should be administered cautiously in patients with hypertrophy or neoplasm of the prostate.

Antihistamines may infrequently cause cardiovascular adverse effects related to their anticholinergic and local anesthetic (quinidine-like) activities. Tachycardia, palpitation, ECG changes, arrhythmias, hypotension, and hypertension have been reported. Although these effects are uncommon and usually limited to overdosage situations, the manufacturers and some clinicians recommend that therapy with antihistamines be administered cautiously in patients with cardiovascular disease, hypertension, and/or hyperthyroidism.

It has been suggested that the anticholinergic effect of antihistamines may reduce the volume and cause thickening of bronchial secretions, resulting in obstruction of respiratory tract. Some manufacturers and clinicians recommend that therapy with antihistamines be administered cautiously in patients with asthma or chronic obstructive pulmonary disease.

Sympathomimetic agents may cause increases in blood glucose concentrations. These effects are usually transient and slight but may be significant with dosages higher than those normally recommended. Therapy with sympathomimetic agents should be administered cautiously in patients with diabetes mellitus. Closer monitoring of blood glucose concentrations may be appropriate.

Antihistamines often have anticholinergic activity, to which elderly patients are particularly sensitive. Therapy with antihistamines should be administered cautiously, if at all, in patients with preexisting conditions that are likely to be exacerbated by anticholinergic activity, such as urinary retention or obstruction; angle-closure glaucoma, untreated intraocular hypertension, or uncontrolled primary open-angle glaucoma; and gastrointestinal obstructive disorders. Conventional, first-generation antihistamines such as the ethanolamines (bromodiphenhydramine, carbinoxamine, clemastine, dimenhydrinate, diphenhydramine, doxylamine, phenyltoloxamine) tend to exhibit substantial anticholinergic effects. In contrast, the newer, relatively nonsedating antihistamines (e.g., cetirizine, fexofenadine, loratadine) reportedly have low to minimal anticholinergic activity at normally recommended dosages and may be appropriate alternatives.

Sympathomimetic agents can induce transient mydriasis via stimulation of alpha-1 adrenergic receptors. In patients with anatomically narrow angles or narrow-angle glaucoma, pupillary dilation can provoke an acute attack. In patients with other forms of glaucoma, mydriasis may occasionally increase intraocular pressure. Therapy with sympathomimetic agents should be administered cautiously in patients with or predisposed to glaucoma, particularly narrow-angle glaucoma.

Antihistamines often have anticholinergic activity, to which elderly patients are particularly sensitive. Therapy with antihistamines should be administered cautiously, if at all, in patients with preexisting conditions that are likely to be exacerbated by anticholinergic activity, such as urinary retention or obstruction; angle-closure glaucoma, untreated intraocular hypertension, or uncontrolled primary open-angle glaucoma; and gastrointestinal obstructive disorders. Conventional, first-generation antihistamines such as the ethanolamines (bromodiphenhydramine, carbinoxamine, clemastine, dimenhydrinate, diphenhydramine, doxylamine, phenyltoloxamine) tend to exhibit substantial anticholinergic effects. In contrast, the newer, relatively nonsedating antihistamines (e.g., cetirizine, fexofenadine, loratadine) reportedly have low to minimal anticholinergic activity at normally recommended dosages and may be appropriate alternatives.

Antihistamines may infrequently cause cardiovascular adverse effects related to their anticholinergic and local anesthetic (quinidine-like) activities. Tachycardia, palpitation, ECG changes, arrhythmias, hypotension, and hypertension have been reported. Although these effects are uncommon and usually limited to overdosage situations, the manufacturers and some clinicians recommend that therapy with antihistamines be administered cautiously in patients with cardiovascular disease, hypertension, and/or hyperthyroidism.

Antihistamines may infrequently cause cardiovascular adverse effects related to their anticholinergic and local anesthetic (quinidine-like) activities. Tachycardia, palpitation, ECG changes, arrhythmias, hypotension, and hypertension have been reported. Although these effects are uncommon and usually limited to overdosage situations, the manufacturers and some clinicians recommend that therapy with antihistamines be administered cautiously in patients with cardiovascular disease, hypertension, and/or hyperthyroidism.

Limited pharmacokinetic data are available for the older, first-generation antihistamines. Many appear to be primarily metabolized by the liver, and both parent drugs and metabolites are excreted in the urine. Patients with renal and/or liver disease may be at greater risk for adverse effects from antihistamines due to drug and metabolite accumulation. Therapy with antihistamines should be administered cautiously in such patients. Lower initial dosages may be appropriate.

Topically applied beta-adrenergic receptor blocking agents (aka beta-blockers) are systemically absorbed, with the potential for producing clinically significant systemic effects even at low or undetectable plasma levels. In the nervous and musculoskeletal systems, beta blockade may potentiate muscle weakness consistent with certain myasthenic symptoms such as diplopia, ptosis, and generalized weakness. Several beta-blockers have been associated rarely with aggravation of muscle weakness in patients with preexisting myasthenia gravis or myasthenic symptoms.

Sympathomimetic agents may cause or worsen urinary difficulty in patients with prostate enlargement due to smooth muscle contraction in the bladder neck via stimulation of alpha-1 adrenergic receptors. Therapy with sympathomimetic agents should be administered cautiously in patients with hypertrophy or neoplasm of the prostate.

Limited pharmacokinetic data are available for the older, first-generation antihistamines. Many appear to be primarily metabolized by the liver, and both parent drugs and metabolites are excreted in the urine. Patients with renal and/or liver disease may be at greater risk for adverse effects from antihistamines due to drug and metabolite accumulation. Therapy with antihistamines should be administered cautiously in such patients. Lower initial dosages may be appropriate.

Antihistamines often have anticholinergic activity, to which elderly patients are particularly sensitive. Therapy with antihistamines should be administered cautiously, if at all, in patients with preexisting conditions that are likely to be exacerbated by anticholinergic activity, such as urinary retention or obstruction; angle-closure glaucoma, untreated intraocular hypertension, or uncontrolled primary open-angle glaucoma; and gastrointestinal obstructive disorders. Conventional, first-generation antihistamines such as the ethanolamines (bromodiphenhydramine, carbinoxamine, clemastine, dimenhydrinate, diphenhydramine, doxylamine, phenyltoloxamine) tend to exhibit substantial anticholinergic effects. In contrast, the newer, relatively nonsedating antihistamines (e.g., cetirizine, fexofenadine, loratadine) reportedly have low to minimal anticholinergic activity at normally recommended dosages and may be appropriate alternatives.