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NIFEdipine（EXTENDED-RELEASE）TABLETS, USP(七)
erapeutic concentrations has no effect on cytochrome P450 enzymes, interactions with drugs that inhibit or are metabolized by those enzymes would not be expected.
Beta-Blockers
Nifedipine extended-release tablets were well tolerated when administered in combination with beta-blockers in 187 hypertensive patients in a placebo-controlled clinical trial. However, there have been occasional literature reports suggesting that the combination nifedipine and beta-adrenergic blocking drugs may increase the likelihood of congestive heart failure, severe hypotension or exacerbation of angina in patients with cardiovascular disease. Clinical monitoring is recommended and a dose adjustment of nifedipine should be considered.
Timolol
Hypotension is more likely to occur if dihydropryridine calcium antagonists such as nifedipine are coadministered with timolol.
Central Alpha1-Blockers
Doxazosin
Healthy volunteers participating in a multiple dose doxazosin-nifedipine interaction study received 2 mg doxazosin q.d. alone or combined with 20 mg nifedipine extended-release b.i.d. Coadministration of nifedipine resulted in a decrease in AUC and Cmax of doxazosin to 83% and 86% of the values in the absence of nifedipine, respectively. In the presence of doxazosin, AUC and Cmax of nifedipine were increased by factors of 1.13 and 1.23, respectively. Compared to nifedipine monotherapy, blood pressure was lower in the presence of doxazosin. Blood pressure should be monitored when doxazosin is coadministered with nifedipine, and dose reduction of nifedipine considered.
Digitalis
Digoxin
The simultaneous administration of nifedipine and digoxin may lead to reduced clearance resulting in an increase in plasma concentrations of digoxin. Since there have been isolated reports of patients with elevated digoxin levels, and there is a possible interaction between digoxin and nifedipine extended-release tablets, it is recommended that digoxin levels be monitored when initiating, adjusting and discontinuing nifedipine extended-release tablets to avoid possible over- or under-digitalization.
Antithrombotics
Coumarins
There have been rare reports of increased prothrombin time in patients taking coumarin anticoagulants to whom nifedipine was administered. However the relationship to nifedipine therapy is uncertain.
Platelet Aggregation Inhibitors
Clopidogrel
No clinically significant pharmacodynamic interactions were observed when clopidrogrel was coadministered with nifedipine.
Tirofiban
Coadministration of nifedipine did not alter the exposure to tirofiban importantly.
Other
Diuretics, PDE5 Inhibitors, Alpha-Methyldopa
Nifedipine may increase the blood pressure lowering effect of these concomitantly administered agents.
Non-Cardiovascular Drugs
Antifungal Drugs
Ketoconazole, itraconazole and fluconazole are CYP3A inhibitors and can inhibit the metabolism of nifedipine and increase the exposure to nifedipine during concomitant therapy. Blood pressure should be monitored and a dose reduction of nifedipine considered.
Antisecretory Drugs
Omeprazole
In healthy volunteers receiving a single dose of 10 mg nifedipine, AUC and Cmax of nifedipine after pretreatment with omeprazole 20 mg q.d. for 8 days were 1.26 and 0.87 times those after pre-treatment with placebo. Pretreatment with or coadministration of omeprazole did not impact the effect of nifedi |
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