Drug Interactions between chlorpheniramine / guaifenesin / phenylephrine and quazepam

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.

GENERALLY AVOID: Acute alcohol ingestion may potentiate the CNS depression and other CNS effects of many benzodiazepines. Tolerance may develop with chronic ethanol use. The mechanism may be decreased clearance of the benzodiazepines because of CYP450 hepatic enzyme inhibition. Also, it has been suggested that the cognitive deficits induced by benzodiazepines may be increased in patients who chronically consume large amounts of alcohol.

MONITOR: Grapefruit juice may increase the plasma concentrations of orally administered drugs that are substrates of the CYP450 3A4 isoenzyme. However, the interaction seems to affect primarily those drugs that undergo significant presystemic metabolism by CYP450 3A4 (i.e., drugs with low oral bioavailability), presumably due to the fact that grapefruit juice inhibits intestinal rather than hepatic CYP450 3A4. Because pharmacokinetic interactions involving grapefruit juice are often subject to a high degree of interpatient variability, the extent to which a given patient may be affected is difficult to predict.

MANAGEMENT: Patients should be advised to avoid alcohol during benzodiazepine therapy. Patients who regularly consume grapefruit or grapefruit juice should be monitored for adverse effects and altered plasma concentrations of drugs that undergo significant presystemic metabolism by CYP450 3A4. Grapefruit and grapefruit juice should be avoided if an interaction is suspected. Orange juice is not expected to interact with these drugs.

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.

The use of benzodiazepines with alcohol is not recommended. Patients with acute alcohol intoxication exhibit depressed vital signs. The central nervous system depressant effects of benzodiazepines may be additive with those of alcohol, and severe respiratory depression and death may occur. Therapy with benzodiazepines should be administered cautiously in patients who might be prone to acute alcohol intake.

Benzodiazepines may cause respiratory depression and apnea, usually when given in high dosages and/or by intravenous administration. However, some patients may be susceptible at commonly used dosages, including the elderly, debilitated or severely ill patients, those receiving other CNS depressants, and those with limited ventilatory reserve, chronic pulmonary insufficiency or other respiratory disorders. Therapy with benzodiazepines should be administered cautiously in these patients. Appropriate monitoring and individualization of dosage are particularly important, and equipment for resuscitation should be immediately available if the parenteral route is used. Benzodiazepines, especially injectable formulations, should generally be avoided in patients with sleep apnea, severe respiratory insufficiency, or hypoxia.

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.

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.

Benzodiazepines have the potential to cause dependence and abuse. Tolerance as well as physical and psychological dependence can develop, particularly after prolonged use and/or excessive dosages. However, abrupt cessation following continual use of as few as 6 weeks at therapeutic levels has occasionally precipitated withdrawal symptoms. Addiction- prone individuals, such as those with a history of alcohol or substance abuse, should be under careful surveillance when treated with benzodiazepines. It may be prudent to refrain from dispensing large quantities of medication to these patients. After prolonged use or if dependency is suspected, withdrawal of benzodiazepine therapy should be undertaken gradually using a dosage- tapering schedule. If withdrawal symptoms occur, temporary reinstitution of benzodiazepines may be necessary.

The manufacturers consider the use of benzodiazepines to be contraindicated in patients with acute angle-closure glaucoma or untreated open-angle glaucoma. These agents do not possess anticholinergic activity but have very rarely been associated with increased intraocular pressure.

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.

Benzodiazepines are metabolized by the liver, and the metabolites are excreted in the urine. Chlordiazepoxide, clorazepate, diazepam, flurazepam and quazepam undergo oxidative N-dealkylation to active metabolites that are substantially longer-acting than the parent compound. These metabolites then undergo further biotransformation to pharmacologically inactive products before excretion by the kidney. Therapy with benzodiazepines should be administered cautiously at lower initial dosages in patients with impaired renal and/or hepatic function. Agents that are converted to weakly active, short-acting, or inactive metabolites may be preferable in hepatic impairment. Lorazepam, oxazepam and temazepam are conjugated to inactive metabolites, while alprazolam, estazolam and triazolam undergo hydroxylation to weakly active or inactive metabolites.

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.

Benzodiazepines may cause respiratory depression and apnea, usually when given in high dosages and/or by intravenous administration. However, some patients may be susceptible at commonly used dosages, including the elderly, debilitated or severely ill patients, those receiving other CNS depressants, and those with limited ventilatory reserve, chronic pulmonary insufficiency or other respiratory disorders. Therapy with benzodiazepines should be administered cautiously in these patients. Appropriate monitoring and individualization of dosage are particularly important, and equipment for resuscitation should be immediately available if the parenteral route is used. Benzodiazepines, especially injectable formulations, should generally be avoided in patients with sleep apnea, severe respiratory insufficiency, or hypoxia.

Benzodiazepines are metabolized by the liver, and the metabolites are excreted in the urine. Chlordiazepoxide, clorazepate, diazepam, flurazepam and quazepam undergo oxidative N-dealkylation to active metabolites that are substantially longer-acting than the parent compound. These metabolites then undergo further biotransformation to pharmacologically inactive products before excretion by the kidney. Therapy with benzodiazepines should be administered cautiously at lower initial dosages in patients with impaired renal and/or hepatic function. Agents that are converted to weakly active, short-acting, or inactive metabolites may be preferable in hepatic impairment. Lorazepam, oxazepam and temazepam are conjugated to inactive metabolites, while alprazolam, estazolam and triazolam undergo hydroxylation to weakly active or inactive metabolites.

Benzodiazepines may cause respiratory depression and apnea, usually when given in high dosages and/or by intravenous administration. However, some patients may be susceptible at commonly used dosages, including the elderly, debilitated or severely ill patients, those receiving other CNS depressants, and those with limited ventilatory reserve, chronic pulmonary insufficiency or other respiratory disorders. Therapy with benzodiazepines should be administered cautiously in these patients. Appropriate monitoring and individualization of dosage are particularly important, and equipment for resuscitation should be immediately available if the parenteral route is used. Benzodiazepines, especially injectable formulations, should generally be avoided in patients with sleep apnea, severe respiratory insufficiency, or hypoxia.

The use of benzodiazepines in patients with seizure disorders may increase the incidence or precipitate the onset of generalized tonic-clonic seizures (grand mal). Appropriate anticonvulsant medication might need to be initiated or the dosage increased. Abrupt cessation of benzodiazepine therapy may precipitate seizures and other withdrawal symptoms, particularly after prolonged use and/or excessive dosages. Status epilepticus may occur in patients with a history of seizures withdrawn rapidly from benzodiazepine therapy. Following chronic administration, cessation of benzodiazepine therapy should occur gradually with incrementally reduced dosages. Patients should be advised not to discontinue medication without first consulting with the physician.

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.

Benzodiazepines depress the central nervous system and may cause or exacerbate mental depression and cause suicidal behavior and ideation. Episodes of mania and hypomania have also been reported in depressed patients treated with some of these agents. Therapy with benzodiazepines should be administered cautiously in patients with a history of depression or other psychiatric disorders. Patients should be monitored for any changes in mood or behavior. It may be prudent to refrain from dispensing large quantities of medication to these patients.

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.

Paradoxical reactions, including excitability, irritability, aggressive behavior, agitation, nervousness, hostility, anxiety, sleep disturbances, nightmares and vivid dreams, have been reported with the use of benzodiazepines in psychiatric patients and pediatric patients with hyperactive aggressive disorders. Such patients should be monitored for signs of paradoxical stimulation during therapy with benzodiazepines. The manufacturers do not recommend the use of benzodiazepines for the treatment of psychosis.

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.

The plasma half-lives of benzodiazepines may be prolonged in obese patients, presumably due to increased distribution into fat. Marked increases in distribution (> 100%) have been reported for diazepam and midazolam, and moderate increases (25% to 100%) for alprazolam, lorazepam, and oxazepam. Therapy with benzodiazepines should be administered cautiously in obese patients, with careful monitoring of CNS status. Longer dosing intervals may be appropriate. When dosing by weight, loading doses should be based on actual body weight, while maintenance dose should be based on ideal body weight to avoid toxicity.

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.

Benzodiazepines depress the central nervous system and may cause or exacerbate mental depression and cause suicidal behavior and ideation. Episodes of mania and hypomania have also been reported in depressed patients treated with some of these agents. Therapy with benzodiazepines should be administered cautiously in patients with a history of depression or other psychiatric disorders. Patients should be monitored for any changes in mood or behavior. It may be prudent to refrain from dispensing large quantities of medication to these patients.

Paradoxical reactions, including excitability, irritability, aggressive behavior, agitation, nervousness, hostility, anxiety, sleep disturbances, nightmares and vivid dreams, have been reported with the use of benzodiazepines in psychiatric patients and pediatric patients with hyperactive aggressive disorders. Such patients should be monitored for signs of paradoxical stimulation during therapy with benzodiazepines. The manufacturers do not recommend the use of benzodiazepines for the treatment of psychosis.

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.

Sleep disturbances may be the presenting manifestation of a physical and/or psychiatric disorder. The symptomatic treatment of insomnia should be initiated only after a careful evaluation of the patient. The failure of insomnia to remit after 7 to 10 days of treatment may indicate the presence of a primary psychiatric or medical illness that should be evaluated. Worsening of insomnia with the emergence of new thinking or behavior abnormalities may be the consequence of an unrecognized disorder.

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.