"What are calcium channel blockers (CCBs) and how do they work?
Calcium channel blockers are drugs that block the entry of calcium into the muscle cells of the heart and arteries.
- The entry of calcium is critical for"...
The following adverse reactions are described elsewhere in labeling:
- Worsening angina or myocardial infarction. [see WARNINGS AND PRECAUTIONS]
- Worsening heart failure. [see WARNINGS AND PRECAUTIONS]
- Worsening AV block. [see CONTRAINDICATIONS]
Clinical Trials Experience
Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The adverse reaction information from clinical trials does, however, provide a basis for identifying the adverse events that appear to be related to drug use and for approximating rates.
Hypertension and Angina
In the MERIT-HF study comparing TOPROL XL in daily doses up to 200 mg (mean dose 159 mg once-daily; n=1990) to placebo (n=2001), 10.3% of TOPROL-XL patients discontinued for adverse reactions vs. 12.2% of placebo patients.
The table below lists adverse reactions in the MERIT-HF study that occurred at an incidence of ≥ 1% in the TOPROL-XL group and greater than placebo by more than 0.5%, regardless of the assessment of causality.
Adverse Reactions Occurring in the MERIT-HF Study at an Incidence
≥ 1 % in the TOPROL-XL Group and Greater Than Placebo by More Than 0.5 %
% of patients
% of patients
|Accident and/or injury||1.4||0.8|
Post-operative Adverse Events
In a randomized, double-blind, placebo-controlled trial of 8351 patients with or at risk for atherosclerotic disease undergoing non-vascular surgery and who were not taking beta–blocker therapy, TOPROL-XL 100 mg was started 2 to 4 hours prior to surgery then continued for 30 days at 200 mg per day. TOPROL-XL use was associated with a higher incidence of bradycardia (6.6% vs. 2.4%; HR 2.74; 95% CI 2.19, 3.43), hypotension (15% vs. 9.7%; HR 1.55; 95% CI 1.37, 1.74), stroke (1.0% vs. 0.5%; HR 2.17; 95% CI 1.26, 3.74) and death (3.1% vs. 2.3%; HR 1.33; 95% CI 1.03, 1.74) compared to placebo.
The following adverse reactions have been identified during post-approval use of TOPROL XL or immediate-release metoprolol. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Hypersensitive Reactions: Pruritus.
Miscellaneous: Musculoskeletal pain, arthralgia, blurred vision, decreased libido, male impotence, tinnitus, reversible alopecia, agranulocytosis, dry eyes, worsening of psoriasis, Peyronie's disease, sweating, photosensitivity, taste disturbance
Potential Adverse Reactions: In addition, there are adverse reactions not listed above that have been reported with other beta-adrenergic blocking agents and should be considered potential adverse reactions to TOPROL-XL.
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, clouded sensorium, and decreased performance on neuropsychometrics.
Hematologic: Agranulocytosis, nonthrombocytopenic purpura, thrombocytopenic purpura.
Hypersensitive Reactions: Laryngospasm, respiratory distress.
Laboratory Test Findings
Clinical laboratory findings may include elevated levels of serum transaminase, alkaline phosphatase, and lactate dehydrogenase.
Read the Toprol XL (metoprolol succinate) Side Effects Center for a complete guide to possible side effects
Catecholamine Depleting Drugs
Catecholamine depleting drugs (eg, reserpine, monoamine oxidase (MAO) inhibitors) may have an additive effect when given with beta-blocking agents. Observe patients treated with TOPROL-XL plus a catecholamine depletor for evidence of hypotension or marked bradycardia, which may produce vertigo, syncope, or postural hypotension.
Drugs that inhibit CYP2D6 such as quinidine, fluoxetine, paroxetine, and propafenone are likely to increase metoprolol concentration. In healthy subjects with CYP2D6 extensive metabolizer phenotype, coadministration of quinidine 100 mg and immediate-release metoprolol 200 mg tripled the concentration of S-metoprolol and doubled the metoprolol elimination half-life. In four patients with cardiovascular disease, coadministration of propafenone 150 mg t.i.d. with immediate-release metoprolol 50 mg t.i.d. resulted in two- to five-fold increases in the steady-state concentration of metoprolol. These increases in plasma concentration would decrease the cardioselectivity of metoprolol.
Digitalis, Clonidine, and Calcium Channel Blockers
Digitalis glycosides, clonidine, diltiazem and verapamil slow atrioventricular conduction and decrease heart rate. Concomitant use with beta blockers can increase the risk of bradycardia.
If clonidine and a beta blocker, such as metoprolol are coadministered, withdraw the beta-blocker several days before the gradual withdrawal of clonidine because beta-blockers may exacerbate the rebound hypertension that can follow the withdrawal of clonidine. If replacing clonidine by beta-blocker therapy, delay the introduction of beta-blockers for several days after clonidine administration has stopped [see WARNINGS AND PRECAUTIONS].
Read the Toprol XL Drug Interactions Center for a complete guide to possible interactions
Last reviewed on RxList: 11/14/2012
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