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Can you take Benadryl with Guanfacine?

1 drug interaction and 27 additional warnings found for the following 2 drugs:

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Drug interactions

Moderate drug interactions

Moderate:

diphenhydrAMINE guanFACINE

Applies to: Benadryl (diphenhydramine) and guanfacine

DiphenhydrAMINE and guanFACINE may have additive effects in lowering your blood pressure.

You may experience headache, dizziness, lightheadedness, fainting, or changes in pulse or heart rate, especially when treatment is started, the dose is changed, or treatment is restarted.

Tell your doctor promptly if these symptoms occur and seek urgent medical help if you faint or have severe dizziness.

Avoid driving or operating hazardous machinery until you know how the medications affect you, and use caution when getting up from a sitting or lying position.

It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Food/lifestyle interactions

Major food/lifestyle interactions

Major:

guanFACINE Food/Lifestyle

Applies to: guanfacine

Avoid consuming grapefruit or grapefruit juice during treatment with guanFACINE, as it may increase blood levels and effects of the medication. This may cause blood pressure to fall excessively, especially when you rise from a sitting or lying position. The risk of other side effects such as drowsiness, dizziness, lightheadedness, fainting, headache, palpitations, and heart rate changes may also increase.

Additionally, you should avoid or limit the use of alcohol while being treated with guanFACINE. Combining the medication with alcohol can intensify sedative and blood pressure lowering effects, which may increase the risk of falls and injury.

Avoid driving or operating hazardous machinery until you know how the medication affects you, and use caution when getting up from a sitting or lying position.

If you are using a long-acting or extended-release formulation of the medication, make sure you do not take it with a high-fat meal. Doing so results in increased absorption and elevated blood levels of the medication.

Talk to your doctor or pharmacist if you have any questions or concerns.

Moderate food/lifestyle interactions

Moderate:

diphenhydrAMINE Alcohol (Ethanol)

Applies to: Benadryl (diphenhydramine)

Ask your doctor before using diphenhydrAMINE together with ethanol (alcohol).

Use alcohol cautiously. Alcohol may increase drowsiness and dizziness while you are taking diphenhydrAMINE.

You should be warned not to exceed recommended dosages and to avoid activities requiring mental alertness.

If your doctor prescribes these medications together, you may need a dose adjustment to safely take this combination.

It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Disease interactions

25 potential interactions Applies to: 17 conditions, including Depression, Asthma, COPD, Hypotension, and Hyperthyroidism.

Asthma

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with Asthma.

Oral anxiolytic, sedative, and hypnotic agents may cause respiratory depression and apnea when given in high dosages or following acute overdose. 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 anxiolytic, sedative, and hypnotic agents should be administered cautiously in these patients. Appropriate monitoring and individualization of dosage are recommended.

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with Asthma.

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.

Cardiovascular Conditions and Disorders

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with Cardiovascular Conditions and Disorders.

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.

Cerebrovascular Insufficiency

Moderate:

guanfacine

guanFACINE has a moderate potential interaction with Cerebrovascular Insufficiency.

Central alpha-2 adrenoreceptor agonists reduce sympathetic outflow from the central nervous system, resulting in decreases in heart rate, peripheral and renovascular resistance, and blood pressure. Therapy with these agents should be administered cautiously in patients with hypotension or conditions that may be exacerbated by decreased blood pressure and perfusion, such as coronary insufficiency, peripheral vascular disease (e.g., Raynaud's syndrome), cerebrovascular disease, or recent myocardial infarction.

COPD

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with COPD.

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.

Depression

Major:

Benadryl

The diphenhydrAMINE in Benadryl has a major potential interaction with Depression.

A variety of abnormal thinking and behavior changes have been reported to occur in association with the use of most anxiolytics, sedatives and hypnotics. Some of these changes include decreased inhibition, aggressiveness, agitation, and hallucinations. These drugs can cause or exacerbate mental depression and cause suicidal behavior and ideation. Therapy with these drugs 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.

Moderate:

guanfacine

guanFACINE has a moderate potential interaction with Depression.

Central alpha-2 adrenoreceptor agonists may occasionally cause mental depression and should be used cautiously in patients with a history of depression.

Gastrointestinal Obstruction

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with Gastrointestinal Obstruction.

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.

Glaucoma/Intraocular Hypertension

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with Glaucoma/Intraocular Hypertension.

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.

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with Glaucoma/Intraocular Hypertension.

Some hypnotic drugs can have an anticholinergic effect and should be used with caution in patients with glaucoma, and trouble urinating due to retention or enlarged prostate.

Heart Block

Moderate:

guanfacine

guanFACINE has a moderate potential interaction with Heart Block.

Central alpha-2 adrenoreceptor agonists reduce sympathetic outflow from the central nervous system. Heart rate is decreased, which may lead to or exacerbate sinus bradycardia and atrioventricular block. Therapy with central alpha-2 adrenoreceptor agonists should be administered cautiously in patients with conduction disturbances such as sinus node dysfunction or AV nodal disease.

Hyperkinetic Syndrome of Childhood

Moderate:

guanfacine

guanFACINE has a moderate potential interaction with Hyperkinetic Syndrome of Childhood.

The safety and effectiveness of guanfacine in children under 12 years of age has not been demonstrated and its use in this age group is not recommended. However, there have been some spontaneous postmarketing reports of mania and aggressive behavioral changes in pediatric patients with attention- deficit hyperactivity disorder (ADHD) that received this drug. All patients had medical or family risks of bipolar disorder, and all of them recovered after treatment discontinuation. Hallucinations have also been reported in pediatric patients receiving guanfacine for the treatment of ADHD.

Hyperthyroidism

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with 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.

Hypotension

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with Hypotension.

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.

Moderate:

guanfacine

guanFACINE has a moderate potential interaction with Hypotension.

Central alpha-2 adrenoreceptor agonists reduce sympathetic outflow from the central nervous system, resulting in decreases in heart rate, peripheral and renovascular resistance, and blood pressure. Therapy with these agents should be administered cautiously in patients with hypotension or conditions that may be exacerbated by decreased blood pressure and perfusion, such as coronary insufficiency, peripheral vascular disease (e.g., Raynaud's syndrome), cerebrovascular disease, or recent myocardial infarction.

Ischemic Heart Disease

Moderate:

guanfacine

guanFACINE has a moderate potential interaction with Ischemic Heart Disease.

Central alpha-2 adrenoreceptor agonists reduce sympathetic outflow from the central nervous system, resulting in decreases in heart rate, peripheral and renovascular resistance, and blood pressure. Therapy with these agents should be administered cautiously in patients with hypotension or conditions that may be exacerbated by decreased blood pressure and perfusion, such as coronary insufficiency, peripheral vascular disease (e.g., Raynaud's syndrome), cerebrovascular disease, or recent myocardial infarction.

Liver Disease

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with Liver Disease.

In general, anxiolytics, sedatives and hypnotics are extensively metabolized by the liver. Their plasma clearance may be decreased and their half-life prolonged in patients with impaired hepatic function. Therapy with these drugs should be administered cautiously in patients with liver disease (some are not recommended in severe liver impairment), and the dosage should be adjusted accordingly. Laboratory testing is recommended prior and during treatment.

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with Liver Disease.

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.

Moderate:

guanfacine

guanFACINE has a moderate potential interaction with Liver Disease.

Normally, approximately 50% of a guanfacine dose is eliminated unchanged by the kidney and the rest metabolized by the liver. However, neither the parent drug nor its metabolites accumulate significantly during chronic dosing in patients with severe renal impairment due to increased hepatic metabolism of the drug in these patients. Thus, initial dosage adjustments are generally not necessary in renal impairment. Dosage titration, however, should be made cautiously if hepatic function is also compromised. The pharmacokinetics of guanfacine has not been studied in patients with liver disease. The manufacturer recommends caution when the drug is used in such patients.

Peripheral Arterial Disease

Moderate:

guanfacine

guanFACINE has a moderate potential interaction with Peripheral Arterial Disease.

Central alpha-2 adrenoreceptor agonists reduce sympathetic outflow from the central nervous system, resulting in decreases in heart rate, peripheral and renovascular resistance, and blood pressure. Therapy with these agents should be administered cautiously in patients with hypotension or conditions that may be exacerbated by decreased blood pressure and perfusion, such as coronary insufficiency, peripheral vascular disease (e.g., Raynaud's syndrome), cerebrovascular disease, or recent myocardial infarction.

Renal Dysfunction

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with Renal Dysfunction.

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.

Moderate:

guanfacine

guanFACINE has a moderate potential interaction with Renal Dysfunction.

Normally, approximately 50% of a guanfacine dose is eliminated unchanged by the kidney and the rest metabolized by the liver. However, neither the parent drug nor its metabolites accumulate significantly during chronic dosing in patients with severe renal impairment due to increased hepatic metabolism of the drug in these patients. Thus, initial dosage adjustments are generally not necessary in renal impairment. Dosage titration, however, should be made cautiously if hepatic function is also compromised. The pharmacokinetics of guanfacine has not been studied in patients with liver disease. The manufacturer recommends caution when the drug is used in such patients.

Sinus Node Dysfunction

Moderate:

guanfacine

guanFACINE has a moderate potential interaction with Sinus Node Dysfunction.

Central alpha-2 adrenoreceptor agonists reduce sympathetic outflow from the central nervous system. Heart rate is decreased, which may lead to or exacerbate sinus bradycardia and atrioventricular block. Therapy with central alpha-2 adrenoreceptor agonists should be administered cautiously in patients with conduction disturbances such as sinus node dysfunction or AV nodal disease.

Urinary Retention

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with Urinary Retention.

Some hypnotic drugs can have an anticholinergic effect and should be used with caution in patients with glaucoma, and trouble urinating due to retention or enlarged prostate.

Moderate:

Benadryl

The diphenhydrAMINE in Benadryl has a moderate potential interaction with Urinary Retention.

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.

More resources

Benadryl

A total of 493 drugs are known to interact with Benadryl.

guanfacine

A total of 535 drugs are known to interact with guanfacine.

Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.