Nefazodone Hydrochloride

Listed in CONTRAINDICATIONS and WARNINGS sections, indicating contraindicated use with nefazodone.

Listed in CONTRAINDICATIONS and WARNINGS sections, indicating contraindicated use with nefazodone.

Marked increases in buspirone plasma concentrations (up to 20-fold in Cmax, 50-fold in AUC) with significant decreases in metabolite. Subjects experienced lightheadedness, asthenia, dizziness, somnolence.

Nefazodone did not potentiate cognitive and psychomotor effects in normal subjects, but concomitant use not advised in depressed patients.

HMG-CoA Reductase Inhibitors – When single 40 mg doses of simvastatin or atorvastatin, both substrates of CYP3A4, were given to healthy adult volunteers who had received nefazodone hydrochloride, 200 mg BID for 6 days, approximately 20 fold increases in plasma concentrations of simvastatin and simvastatin acid and 3 to 4 fold increases in plasma concentrations of atorvastatin and atorvastatin lactone were seen. Caution should be used if nefazodone is administered in combination with HMG-CoA reductase inhibitors that are metabolized by CYP3A4, such as simvastatin, atorvastatin, and lovastatin, and dosage adjustments of these HMG-CoA reductase inhibitors are recommended. This is consistent with the interactions observed between nefazodone and triazolam, alprazolam, buspirone, atorvastatin, and simvastatin, drugs metabolized by this isozyme.

Nefazodone decreased haloperidol apparent clearance by 35% with unknown clinical significance. Dosage adjustment of haloperidol may be necessary.

There have been rare reports of rhabdomyolysis involving patients receiving the combination of nefazodone and either simvastatin or lovastatin, also a substrate of CYP3A4 (see ADVERSE REACTIONS , Postintroduction Clinical Experience ). Caution should be used if nefazodone is administered in combination with HMG-CoA reductase inhibitors that are metabolized by CYP3A4, such as simvastatin, atorvastatin, and lovastatin, and dosage adjustments of these HMG-CoA reductase inhibitors are recommended.

HMG-CoA Reductase Inhibitors – When single 40 mg doses of simvastatin or atorvastatin, both substrates of CYP3A4, were given to healthy adult volunteers who had received nefazodone hydrochloride, 200 mg BID for 6 days, approximately 20 fold increases in plasma concentrations of simvastatin and simvastatin acid and 3 to 4 fold increases in plasma concentrations of atorvastatin and atorvastatin lactone were seen. There have been rare reports of rhabdomyolysis involving patients receiving the combination of nefazodone and either simvastatin or lovastatin, also a substrate of CYP3A4 (see ADVERSE REACTIONS , Postintroduction Clinical Experience ). Caution should be used if nefazodone is administered in combination with HMG-CoA reductase inhibitors that are metabolized by CYP3A4, such as simvastatin, atorvastatin, and lovastatin, and dosage adjustments of these HMG-CoA reductase inhibitors are recommended.

Nefazodone decreased S-warfarin exposure by 12%, but no effects on prothrombin or bleeding times. Monitoring recommended per standard medical practice.

No changes in pharmacokinetic parameters for either drug when coadministered. No dosage adjustment necessary.

Similarly, there were no changes in the pharmacokinetic parameters of nefazodone or HO-NEF; however, the mean AUC levels of the nefazodone metabolites mCPP and triazole-dione increased by 3 to 6 fold and 1.3 fold, respectively. There were also no changes in the pharmacokinetics of nefazodone or its triazole-dione metabolite, but the AUC and C max of mCPP increased by 44% and 48%, respectively, while the AUC of HO-NEF decreased by 19%. When the two drugs were coadministered, there were no changes in the steady-state pharmacokinetics of either lithium, nefazodone, or its metabolite HO-NEF; however, there were small decreases in the steady-state plasma concentrations of two nefazodone metabolites, mCPP and triazole-dione, which are considered not to be of clinical significance.

Since metabolic interactions are unlikely between nefazodone and HMG-CoA reductase inhibitors that undergo little or no metabolism by the CYP3A4 isozyme, such as pravastatin or fluvastatin, dosage adjustments should not be necessary.

These effects appear to be due to the inhibition of CYP3A4 by nefazodone because, in the same study, nefazodone had no significant effect on the plasma concentrations of pravastatin, which is not metabolized by CYP3A4 to a clinically significant extent. Since metabolic interactions are unlikely between nefazodone and HMG-CoA reductase inhibitors that undergo little or no metabolism by the CYP3A4 isozyme, such as pravastatin or fluvastatin, dosage adjustments should not be necessary.

Propranolol – The coadministration of nefazodone (200 mg BID) and propranolol (40 mg BID) for 5.5 days to healthy male volunteers (n = 18), including 3 poor and 15 extensive CYP2D6 metabolizers, resulted in 30% and 14% reductions in C max and AUC of propranolol, respectively, and a 14% reduction in C max for the metabolite, 4-hydroxypropranolol. The kinetics of nefazodone, hydroxynefazodone, and triazole-dione were not affected by coadministration of propranolol.