"What are beta blockers and how do they work?
Beta blockers, also known as beta-adrenergic blocking agents, are a class of drugs that works by blocking the neurotransmitters norepinephrine and epinephrine from binding to receptors. "...
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Most adverse effects have been mild and transient.
Central Nervous System: Tiredness and dizziness have occurred in about 10 of 100 patients. Depression has been reported in about 5 of 100 patients. Mental confusion and short-term memory loss have been reported. Headache, nightmares, and insomnia have also been reported.
Cardiovascular: Shortness of breath and bradycardia have occurred in approximately 3 of 100 patients. Cold extremities; arterial insufficiency, usually of the Raynaud type; palpitations; congestive heart failure; peripheral edema; and hypotension have been reported in about 1 of 100 patients. Gangrene in patients with pre-existing severe peripheral circulatory disorders has also been reported very rarely. (See CONTRAINDICATIONS, WARNINGS, and PRECAUTIONS.)
Gastrointestinal: Diarrhea has occurred in about 5 of 100 patients. Nausea, dry mouth, gastric pain, constipation, flatulence, and heartburn have been reported in about 1 of 100 patients. Vomiting was a common occurrence. Postmarketing experience reveals very rare reports of hepatitis, jaundice and non-specific hepatic dysfunction. Isolated cases of transaminase, alkaline phosphatase, and lactic dehydrogenase elevations have also been reported.
There have been rare reports of reversible alopecia, agranulocytosis, and dry eyes. Discontinuation of the drug should be considered if any such reaction is not otherwise explicable. There have been very rare reports of weight gain, arthritis, and retroperitoneal fibrosis (relationship to Lopressor (metoprolol tartrate) has not been definitely established).
The oculomucocutaneous syndrome associated with the beta blocker practolol has not been reported with Lopressor (metoprolol tartrate) .
Central Nervous System: Tiredness has been reported in about 1 of 100 patients. Vertigo, sleep disturbances, hallucinations, headache, dizziness, visual disturbances, confusion, and reduced libido have also been reported, but a drug relationship is not clear.
Cardiovascular: In the randomized comparison of Lopressor and placebo described in the CLINICAL PHARMACOLOGY section, the following adverse reactions were reported:
|Hypotension (systolic BP <90 mmHg)||27.4%||23.2%|
|Bradycardia (heart rate <40 beats/min)||15.9%||6.7%|
|Second- or third-degree heart block||4.7%||4.7%|
|First-degree heart block (P-R >0.26 sec)||5.3%||1.9%|
Respiratory: Dyspnea of pulmonary origin has been reported in fewer than 1 of 100 patients.
Gastrointestinal: Nausea and abdominal pain have been reported in fewer than 1 of 100 patients.
Dermatologic: Rash and worsened psoriasis have been reported, but a drug relationship is not clear.
Potential Adverse Reactions
A variety of adverse reactions not listed above have been reported with other beta-adrenergic blocking agents and should be considered potential adverse reactions to Lopressor (metoprolol tartrate) .
Central Nervous System: Reversible mental depression progressing to catatonia; an acute reversible syndrome characterized by disorientation for time and place, short-term memory loss, emotional lability, slightly clouded sensorium, and decreased performance on neuropsychometrics.
Cardiovascular: Intensification of AV block (see CONTRAINDICATIONS).
Hematologic: Agranulocytosis, nonthrombocytopenic purpura, thrombocytopenic purpura.
The following adverse reactions have been reported during postapproval use of Lopressor (metoprolol tartrate) : confusional state, an increase in blood triglycerides and a decrease in High Density Lipoprotein (HDL). Because these reports are from a population of uncertain size and are subject to confounding factors, it is not possible to reliably estimate their frequency.
Read the Lopressor (metoprolol tartrate) Side Effects Center for a complete guide to possible side effects
Catecholamine-depleting drugs (e.g., reserpine) may have an additive effect when given with beta-blocking agents. Patients treated with Lopressor (metoprolol tartrate) plus a catecholamine depletor should therefore be closely observed for evidence of hypotension or marked bradycardia, which may produce vertigo, syncope, or postural hypotension.
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.
Some inhalation anesthetics may enhance the cardiodepressant effect of beta blockers (see WARNINGS, Major Surgery).
Potent inhibitors of the CYP2D6 enzyme may increase the plasma concentration of Lopressor (metoprolol tartrate) . Strong inhibition of CYP2D6 would mimic the pharmacokinetics of CYP2D6 poor metabolizer (see Pharmacokinetics section). Caution should therefore be exercised when coadministering potent CYP2D6 inhibitors with Lopressor (metoprolol tartrate) . Known clinically significant potent inhibitors of CYP2D6 are antidepressants such as fluoxetine, paroxetine or bupropion, antipsychotics such as thioridazine, antiarrhythmics such as quinidine or propafenone, antiretrovirals such as ritonavir, antihistamines such as diphenhydramine, antimalarials such as hydroxychloroquine or quinidine, antifungals such as terbinafine and medications for stomach ulcers such as cimetidine.
If a patient is treated with clonidine and Lopressor (metoprolol tartrate) concurrently, and clonidine treatment is to be discontinued, Lopressor (metoprolol tartrate) should be stopped several days before clonidine is withdrawn. Rebound hypertension that can follow withdrawal of clonidine may be increased in patients receiving concurrent beta-blocker treatment.
Read the Lopressor Drug Interactions Center for a complete guide to possible interactions
Last reviewed on RxList: 5/9/2011
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