LABETALOL Drug Interactions: What You Need to Know
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Drug Interactions (FDA Label)
DRUG INTERACTIONS In one survey, 2.3% of patients taking labetalol hydrochloride in combination with tricyclic antidepressants experienced tremor as compared to 0.7% reported to occur with labetalol hydrochloride alone. The contribution of each of the treatments to this adverse reaction is unknown but the possibility of a drug interaction cannot be excluded. Drugs possessing beta-blocking properties can blunt the bronchodilator effect of beta-receptor agonist drugs in patients with bronchospasm; therefore, doses greater than the normal anti-asthmatic dose of beta-agonist bronchodilator drugs may be required. Cimetidine has been shown to increase the bioavailability of labetalol hydrochloride. Since this could be explained either by enhanced absorption or by an alteration of hepatic metabolism of labetalol hydrochloride, special care should be used in establishing the dose required for blood pressure control in such patients. Synergism has been shown between halothane anesthesia and intravenously administered labetalol hydrochloride. During controlled hypotensive anesthesia using labetalol hydrochloride in association with halothane, high concentrations (3% or above) of halothane should not be used because the degree of hypotension will be increased and because of the possibility of a large reduction in cardiac output and an increase in central venous pressure. The anesthesiologist should be informed when a patient is receiving labetalol hydrochloride. Labetalol hydrochloride blunts the reflex tachycardia produced by nitroglycerin without preventing its hypotensive effect. If labetalol hydrochloride is used with nitroglycerin in patients with angina pectoris, additional antihypertensive effects may occur. Care should be taken if labetalol is used concomitantly with calcium antagonists of the verapamil type. Both digitalis glycosides and beta-blockers slow atrioventricular conduction and decrease heart rate. Concomitant use can increase the risk of bradycardia. Risk of Anaphylactic Reaction While taking beta-blockers, patients with a history of severe anaphylactic reaction to a variety of allergens may be more reactive to repeated challenge, either accidental, diagnostic or therapeutic. Such patients may be unresponsive to the usual doses of epinephrine used to treat allergic reaction.
Drug/Laboratory
Test Interactions The presence of labetalol metabolites in the urine may result in falsely elevated levels of urinary catecholamines, metanephrine, normetanephrine and vanillylmandelic acid (VMA) when measured by fluorimetric or photometric methods. In screening patients suspected of having a pheochromocytoma and being treated with labetalol hydrochloride, a specific method, such as a high performance liquid chromatographic assay with solid phase extraction (e.g. J.
Chromatogr
385:241, 1987) should be employed in determining levels of catecholamines. Labetalol hydrochloride has also been reported to produce a false-positive test for amphetamine when screening urine for the presence of drugs using the commercially available assay methods TOXI-Lab ® A (thin-layer chromatographic assay) and Emit-d.a.u. ® (radioenzymatic assay). When patients being treated with labetalol have a positive urine test for amphetamine using these techniques, confirmation should be made by using more specific methods, such as a gas chromatographic-mass spectrometer technique. Carcinogenesis, Mutagenesis, Impairment of Fertility Long-term oral dosing studies with labetalol hydrochloride for 18 months in mice and for 2 years in rats showed no evidence of carcinogenesis. Studies with labetalol hydrochloride using dominant lethal assays in rats and mice and exposing microorganisms according to modified Ames tests, showed no evidence of mutagenesis.
Pregnancy Teratogenic Effects Pregnancy
Category C Teratogenic studies were performed with labetalol in rats and rabbits at oral doses up to approximately six and four times the maximum recommended human dose (MRHD), respectively. No reproducible evidence of fetal malformations was observed. Increased fetal resorptions were seen in both species at doses approximating the MRHD. A teratology study performed with labetalol in rabbits at intravenous doses up to 1.7 times the MRHD revealed no evidence of drug-related harm to the fetus. There are no adequate and well-controlled studies in pregnant women. Labetalol should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Nonteratogenic Effects
Hypotension, bradycardia, hypoglycemia and respiratory depression have been reported in infants of mothers who were treated with labetalol hydrochloride for hypertension during pregnancy. Oral administration of labetalol to rats during late gestation through weaning at doses of two to four times the MRHD caused a decrease in neonatal survival. Labor and Delivery Labetalol hydrochloride given to pregnant women with hypertension did not appear to affect the usual course of labor and delivery.
Nursing Mothers
Small amounts of labetalol (approximately 0.004% of the maternal dose) are excreted in human milk. Caution should be exercised when labetalol hydrochloride tablets are administered to a nursing woman..
Pediatric Use
Safety and effectiveness in pediatric patients have not been established.
Elderly
Patients As in the general population, some elderly patients (60 years of age and older) have experienced orthostatic hypotension, dizziness or lightheadedness during treatment with labetalol. Because elderly patients are generally more likely than younger patients to experience orthostatic symptoms, they should be cautioned about the possibility of such side effects during treatment with labetalol.
Contraindications
Labetalol Hydrochloride Tablets are contraindicated in patients with:
- bronchial asthma or obstructive airway disease
- decompensated heart failure
- greater than first degree heart block
- cardiogenic shock
- severe bradycardia
- Hypersensitivity reactions, including anaphylaxis, to labetalol
- non-dihydropyridine calcium-channel antagonists
- Bronchial asthma or obstructive airway disease ( 4 )
- Overt cardiac failure ( 4 )
- Greater‑than‑first‑degree heart block ( 4 )
- Cardiogenic shock ( 4 )
- Severe bradycardia ( 4 )
- Non-dihydropyridine calcium-channel antagonists ( 4 )
Related Warnings
AND PRECAUTIONS Monitor patients for symptomatic postural hypotension and syncope after initial dosing or dose increments. ( 5.1 ) Monitor heart rate and rhythm for bradycardia, including sinus pause, heart block, severe bradycardia, and cardiac arrest in patients receiving Labetalol Hydrochloride Tablets. ( 5.2 ) Beta-blockade can depress myocardial contractility and precipitating more severe failure. Avoid use in patients with overt heart failure. ( 5.3 ). Monitor heart rate and rhythm for bradycardia, including sinus pause, heart block, severe bradycardia, and cardiac arrest in patients receiving Labetalol Hydrochloride Tablets. ( 5.2 ) Beta-blockade can depress myocardial contractility and precipitating more severe failure. Avoid use in patients with overt heart failure. ( 5.3 ) Acute exacerbation of coronary artery disease upon cessation of therapy. Do not abruptly discontinue. ( 5.4 ) Avoid use in patients with bronchospastic disease. ( 5.5 ) Beta‑adrenergic blockade may prevent the appearance of premonitory signs and symptoms (e.g., tachycardia) of acute hypoglycemia. ( 5.6 ) Exacerbation of pheochromocytoma: Paradoxical increases in blood pressure may occur. ( 5.7 ) Hepatic necrosis and death have been reported. If the patient develops signs or symptoms of liver injury, institute appropriate treatment and investigate the probable cause. ( 5.8 ) Do not routinely withdraw chronic beta blocker therapy prior to surgery. ( 5.10 )
5.1 Hypotension Monitor patients for symptomatic postural hypotension and syncope after initial dosing or dose increments with Labetalol Hydrochloride Tablets. Elderly patients are generally more likely than younger patients to experience orthostatic symptoms <span class="opacity-50 text-xs">[see Dosage and Administration (2.1) , Use in Specific Populations (8.5) , Clinical Pharmacology (12.2) ]</span>.
5.2 Bradycardia Bradycardia, including sinus pause, heart block, severe bradycardia, and cardiac arrest have occurred with the use of beta blockers. Monitor heart rate and rhythm in patients receiving Labetalol Hydrochloride Tablets.
5.3 Cardiac Failure Sympathetic stimulation is a vital component supporting circulatory function in congestive heart failure. Beta‑blockade carries a potential hazard of further depressing myocardial contractility and precipitating more severe failure.
Avoid Labetalol Hydrochloride
Tablets in patients with overt congestive heart failure. If patients develop signs or symptoms of heart failure during administration, discontinue Labetalol Hydrochloride Tablets and treat appropriately.
5.4 Ischemic Heart Disease Abrupt cessation of therapy with beta blocking agents in patients with coronary artery disease can cause exacerbations of angina pectoris and, in some cases, myocardial infarction has been reported. Therefore, even in the absence of overt angina pectoris, after the discontinuation of Labetalol Hydrochloride Tablets observe patients for development or worsening of angina. If patient experiences angina or angina markedly worsens or if acute coronary insufficiency develops, promptly reinstitute Labetalol Hydrochloride Tablets and manage as unstable angina.
5.5 Reactive Airway Disease and Nonallergic Bronchospasm Avoid use in patients with reactive airways disease.
If Labetalol Hydrochloride
Tablets are used, use the smallest effective dose, to minimize inhibition of endogenous or exogenous beta agonists.
5.6 Hypoglycemia Beta-blockers may prevent early warning signs of hypoglycemia, such as tachycardia, and increase the risk for severe or prolonged hypoglycemia at any time during treatment, especially in patients with diabetes mellitus or children and patients who are fasting (i.e., surgery, not eating regularly, or are vomiting). If severe hypoglycemia occurs, patients should be instructed to seek emergency treatment.
5.7 Use in Patients with Pheochromocytoma Labetalol hydrochloride has been shown to be effective in lowering blood pressure and relieving symptoms in patients with pheochromocytoma; higher than usual doses may be required. However, paradoxical hypertensive responses have been reported in a few patients with this tumor; therefore, blood pressure when administering labetalol hydrochloride to patients with pheochromocytoma.
5.8 Hepatic Injury Severe hepatocellular injury occurs rarely with labetalol therapy. The hepatic injury is usually reversible, but hepatic necrosis and death have been reported. If the patient develops signs or symptoms of liver injury, institute appropriate treatment and investigate the probable cause. Do not restart labetalol in patients without another explanation for the observed liver injury.
5.9 Use in Patients at Risk of Severe Acute Hypersensitivity Reactions Patients at risk of anaphylactic reactions may be more reactive to allergen exposure (accidental, diagnostic, or therapeutic). Patients using beta-blockers may be unresponsive to the usual doses of epinephrine used to treat anaphylactic or anaphylactoid reactions.
Avoid Labetalol Hydrochloride
Tablets in patients at high risk of anaphylactic reactions.
5.10 Major Surgery Do not routinely withdraw chronic beta blocker therapy prior to surgery. The effect of labetalol’s alpha adrenergic activity has not been evaluated in this setting. A synergism between labetalol hydrochloride and halothane anesthesia has been shown [ see Drug Interactions (7.3) ].
5.11 Intraoperative Floppy Iris Syndrome (IFIS) IFIS has been observed during cataract surgery in some patients treated with alpha-1 blockers (labetalol is an alpha/beta blocker). This variant of small pupil syndrome is characterized by the combination of a flaccid iris that billows in response to intraoperative irrigation currents, progressive intraoperative miosis despite preoperative dilation with standard mydriatic drugs, and potential prolapse of the iris toward the phacoemulsification incisions. Inform the patient’s ophthalmologist to be prepared for possible modifications to the surgical technique, such as the utilization of iris hooks, iris dilator rings, or viscoelastic substances.
5.1 Hypotension Monitor patients for symptomatic postural hypotension and syncope after initial dosing or dose increments with Labetalol Hydrochloride Tablets. Elderly patients are generally more likely than younger patients to experience orthostatic symptoms <span class="opacity-50 text-xs">[see Dosage and Administration (2.1) , Use in Specific Populations (8.5) , Clinical Pharmacology (12.2) ]</span>.
5.2 Bradycardia Bradycardia, including sinus pause, heart block, severe bradycardia, and cardiac arrest have occurred with the use of beta blockers. Monitor heart rate and rhythm in patients receiving Labetalol Hydrochloride Tablets.
5.3 Cardiac Failure Sympathetic stimulation is a vital component supporting circulatory function in congestive heart failure. Beta‑blockade carries a potential hazard of further depressing myocardial contractility and precipitating more severe failure.
Avoid Labetalol Hydrochloride
Tablets in patients with overt congestive heart failure. If patients develop signs or symptoms of heart failure during administration, discontinue Labetalol Hydrochloride Tablets and treat appropriately.
5.4 Ischemic Heart Disease Abrupt cessation of therapy with beta blocking agents in patients with coronary artery disease can cause exacerbations of angina pectoris and, in some cases, myocardial infarction has been reported. Therefore, even in the absence of overt angina pectoris, after the discontinuation of Labetalol Hydrochloride Tablets observe patients for development or worsening of angina. If patient experiences angina or angina markedly worsens or if acute coronary insufficiency develops, promptly reinstitute Labetalol Hydrochloride Tablets and manage as unstable angina.
5.5 Reactive Airway Disease and Nonallergic Bronchospasm Avoid use in patients with reactive airways disease.
If Labetalol Hydrochloride
Tablets are used, use the smallest effective dose, to minimize inhibition of endogenous or exogenous beta agonists.
5.6 Hypoglycemia Beta-blockers may prevent early warning signs of hypoglycemia, such as tachycardia, and increase the risk for severe or prolonged hypoglycemia at any time during treatment, especially in patients with diabetes mellitus or children and patients who are fasting (i.e., surgery, not eating regularly, or are vomiting). If severe hypoglycemia occurs, patients should be instructed to seek emergency treatment.
5.7 Use in Patients with Pheochromocytoma Labetalol hydrochloride has been shown to be effective in lowering blood pressure and relieving symptoms in patients with pheochromocytoma; higher than usual doses may be required. However, paradoxical hypertensive responses have been reported in a few patients with this tumor; therefore, blood pressure when administering labetalol hydrochloride to patients with pheochromocytoma.
5.8 Hepatic Injury Severe hepatocellular injury occurs rarely with labetalol therapy. The hepatic injury is usually reversible, but hepatic necrosis and death have been reported. If the patient develops signs or symptoms of liver injury, institute appropriate treatment and investigate the probable cause. Do not restart labetalol in patients without another explanation for the observed liver injury.
5.9 Use in Patients at Risk of Severe Acute Hypersensitivity Reactions Patients at risk of anaphylactic reactions may be more reactive to allergen exposure (accidental, diagnostic, or therapeutic). Patients using beta-blockers may be unresponsive to the usual doses of epinephrine used to treat anaphylactic or anaphylactoid reactions.
Avoid Labetalol Hydrochloride
Tablets in patients at high risk of anaphylactic reactions.