VIRACEPT Drug Interactions

(nelfinavir mesylate)

7 DRUG INTERACTIONS

7.1 Potential for VIRACEPT to Affect Other Drugs

Nelfinavir is an inhibitor of CYP3A. Coadministration of VIRACEPT and drugs primarily metabolized by CYP3A (e.g., dihydropyridine calcium channel blockers, HMG-CoA reductase inhibitors, immunosuppressants, and PDE5 inhibitors) may result in increased plasma concentrations of such drugs that could increase or prolong both its therapeutic and adverse effects (see Tables 3 and 6).

7.2 Potential for Other Drugs to Affect VIRACEPT

Nelfinavir is metabolized by CYP3A and CYP2C19. Coadministration of VIRACEPT and drugs that induce CYP3A or CYP2C19, such as rifampin, may decrease nelfinavir plasma concentrations and reduce its therapeutic effect. Coadministration of VIRACEPT and drugs that inhibit CYP3A or CYP2C19 may increase nelfinavir plasma concentrations.

7.3 Established and Other Potentially Significant Drug Interactions

Table 6 provides the effect on concentrations of VIRACEPT or concomitant drug as a result of coadministration with VIRACEPT. These recommendations are based on either drug interaction studies or predicted interactions due to the expected magnitude of interaction and potential for serious adverse events or loss of efficacy.

Table 6: Established and Other Potentially Significant Drug Interactions: Alteration in Dose or Regimen May Be Recommended Based on Drug Interaction Studies [see Clinical Pharmacology (12.3) (Tables 12 and 13) for magnitude of interaction]

Concomitant Drug Class:
Drug Name		Effect on
Concentration		Clinical Comment
HIV Antiviral Agents: Reverse Transcriptase Inhibitors

Delavirdine

↑ nelfinavir (Cmin)
↓ delavirdine

Concentrations of nelfinavir were increased while concentrations of delavirdine were decreased when the two agents were coadministered. Appropriate doses of the combination, with respect to safety and efficacy, have not been established.

Nevirapine

↓ nelfinavir (Cmin)

Concentrations of nelfinavir were decreased when coadministered with nevirapine. An appropriate dose of nelfinavir with respect to safety and efficacy has not been established.

Didanosine

↔ nelfinavir

There was no change in nelfinavir concentration when coadministered with didanosine. However, it is recommended that didanosine be administered on an empty stomach; therefore, didanosine should be given one hour before or two hours after VIRACEPT (given with food).

HIV Antiviral Agents: Protease Inhibitors

Indinavir

↑ nelfinavir
↑ indinavir

Concentrations of both indinavir and nelfinavir were increased when the two agents were coadministered. Appropriate doses for these combinations, with respect to safety and efficacy, have not been established.

Ritonavir

↑ nelfinavir
↔ ritonavir

Concentrations of nelfinavir were increased when coadministered with ritonavir. An appropriate dose of nelfinavir for this combination, with respect to safety and efficacy, has not been established.

Saquinavir

↑ nelfinavir
↑ saquinavir

Concentrations of both saquinavir and nelfinavir were increased when the two agents were coadministered. Appropriate doses for these combinations, with respect to safety and efficacy, have not been established.

ANTICOAGULANT

Warfarin

Warfarin

Coadministration of warfarin and VIRACEPT may affect concentrations of warfarin. It is recommended that the INR (international normalized ratio) be monitored carefully during treatment with VIRACEPT, especially when commencing therapy.

ANTICONVULSANTS

Carbamazepine Phenobarbital
Phenytoin


↓ nelfinavir

↓ phenytoin

Concentrations of nelfinavir may be decreased. VIRACEPT may not be effective due to decreased nelfinavir plasma concentrations in patients taking these agents concomitantly.
Phenytoin plasma/serum concentrations should be monitored; phenytoin dose may require adjustment to compensate for altered phenytoin concentration.

ANTIDEPRESSANT

Trazodone

↑ trazodone

Concomitant use of trazodone and VIRACEPT may increase plasma concentrations of trazodone. Adverse events of nausea, dizziness, hypotension and syncope have been observed following coadministration of trazodone and ritonavir. If trazodone is used with a CYP3A4 inhibitor such as VIRACEPT, the combination should be used with caution and a lower dose of trazodone should be considered.

ANTIGOUT

Colchicine

↑ colchicines

Patients with renal or hepatic impairment should not be given colchicine with VIRACEPT due to the risk of colchicine toxicity.

Treatment of gout flares –
co- administration of colchicine in patients on VIRACEPT:

0.6 mg (1 tablet) × 1 dose, followed by 0.3 mg (half tablet) 1 hour later. Dose to be repeated no earlier than 3 days.

Prophylaxis of gout-flares –
coadministration of colchicine in patients on VIRACEPT:

If the original colchicine regimen was 0.6 mg twice a day, the regimen should be adjusted to 0.3 mg once a day.
If the original colchicine regimen was 0.6 mg once a day, the regimen should be adjusted to 0.3 mg once every other day.

Treatment of familial Mediterranean fever (FMF)– coadministration of colchicine in patients on VIRACEPT:

Maximum daily dose of 0.6 mg (may be given as 0.3 mg twice a day).

ANTIMYCOBACTERIAL

Rifabutin

↑ rifabutin
↓ nelfinavir
  (750 mg TID)
↔ nelfinavir
  (1250 mg BID)

It is recommended that the dose of rifabutin be reduced to one-half the usual dose when administered with VIRACEPT; 1250 mg BID is the preferred dose of VIRACEPT when coadministered with rifabutin.

ENDOTHELIN RECEPTOR ANTAGONIST

Bosentan

↑ bosentan

Concentrations of bosentan may be increased when coadministered with VIRACEPT. Coadministration of bosentan in patients on VIRACEPT or coadministration of VIRACEPT in patients on bosentan:
Start at or adjust bosentan to 62.5 mg once daily or every other day based upon individual tolerability.

HMG-CoA REDUCTASE INHIBITORS

Atorvastatin
Rosuvastatin

↑ atorvastatin
↑ rosuvastatin

Titrate atorvastatin dose carefully and use the lowest necessary dose; do not exceed atorvastatin 40 mg/day.

IMMUNOSUPPRESSANTS

Cyclosporine
Tacrolimus
Sirolimus

↑ immuno-suppressants
↑ nelfinavir

Concentrations of these immunosuppressants and nelfinavir may be increased by coadministration of these agents with nelfinavir.

INHALED BETA AGONIST

Salmeterol

↑ salmeterol

Concurrent administration of salmeterol with VIRACEPT is not recommended. The combination may result in increased risk of cardiovascular adverse events associated with salmeterol, including QT prolongation, palpitations and sinus tachycardia.

INHALED/NASAL STEROID

Fluticasone

↑ fluticasone

Concomitant use of fluticasone propionate and VIRACEPT may increase plasma concentrations of fluticasone propionate. Use with caution. Consider alternatives to fluticasone propionate, particularly for long-term use.

MACROLIDE ANTIBIOTIC

Azithromycin

↑ azithromycin

Dose adjustment of azithromycin is not recommended, but close monitoring for known side effects such as liver enzyme abnormalities and hearing impairment is warranted.

NARCOTIC ANALGESIC

Methadone

↓ methadone

Concentrations of methadone were decreased when coadministered with VIRACEPT. Dosage of methadone may need to be increased when coadministered with VIRACEPT.

HORMONAL CONTRACEPTIVES

Ethinyl estradiol
Norethindrone

↓ ethinyl estradiol
↓ norethindrone

Concentrations of ethinyl estradiol and norethindrone were decreased when coadministered with VIRACEPT. Alternative or additional contraceptive measures should be used when oral contraceptives containing ethinyl estradiol or norethindrone and VIRACEPT are coadministered.

PDE5 INHIBITORS

Sildenafil
Vardenafil
Tadalafil

↑ PDE5 Inhibitors

Concomitant use of PDE5 inhibitors and VIRACEPT should be undertaken with caution.

May result in an increase in PDE5 inhibitor-associated adverse events, including hypotension, syncope, visual disturbances, and priapism.

Use of PDE5 inhibitors for pulmonary arterial hypertension (PAH):

• Use of sildenafil (REVATIO) is contraindicated when used for the treatment of pulmonary arterial hypertension (PAH) [see Contraindications (4)].

• The following dose adjustments are recommended for use of tadalafil (ADCIRCA™) with VIRACEPT:

Coadministration of ADCIRCA in patients on VIRACEPT or coadministration of VIRACEPT in patients on ADCIRCA:

Start at or adjust ADCIRCA to 20 mg once daily. Increase to 40 mg once daily based upon individual tolerability.

Use of PDE5 inhibitors for erectile dysfunction:

Sildenafil at a single dose not exceeding 25 mg in 48 hours, vardenafil at a single dose not exceeding 2.5 mg in 24 hours, or tadalafil at a single dose not exceeding 10 mg dose in 72 hours, is recommended. Use with increased monitoring for adverse events.

PROTON PUMP INHIBITORS

Omeprazole

↓ nelfinavir

Omeprazole decreases the plasma concentrations of nelfinavir. Concomitant use of proton pump inhibitors and VIRACEPT may lead to a loss of virologic response and development of resistance.

ANTIPSYCHOTICS

Quetiapine

↑ quetiapine

Initiation of VIRACEPT in patients taking quetiapine:
Consider alternative antiretroviral therapy to avoid increases in quetiapine drug exposures. If coadministration is necessary, reduce the quetiapine dose to 1/6 of the current dose and monitor for quetiapine-associated adverse reactions. Refer to the quetiapine prescribing information for recommendations on adverse reaction monitoring.

Initiation of quetiapine in patients taking VIRACEPT:
Refer to the quetiapine prescribing information for initial dosing and titration of quetiapine.

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Drug Interactions

7 DRUG INTERACTIONS

7.1 Potential for VIRACEPT to Affect Other Drugs

Nelfinavir is an inhibitor of CYP3A. Coadministration of VIRACEPT and drugs primarily metabolized by CYP3A (e.g., dihydropyridine calcium channel blockers, HMG-CoA reductase inhibitors, immunosuppressants, and PDE5 inhibitors) may result in increased plasma concentrations of such drugs that could increase or prolong both its therapeutic and adverse effects (see Tables 3 and 6).

7.2 Potential for Other Drugs to Affect VIRACEPT

Nelfinavir is metabolized by CYP3A and CYP2C19. Coadministration of VIRACEPT and drugs that induce CYP3A or CYP2C19, such as rifampin, may decrease nelfinavir plasma concentrations and reduce its therapeutic effect. Coadministration of VIRACEPT and drugs that inhibit CYP3A or CYP2C19 may increase nelfinavir plasma concentrations.

7.3 Established and Other Potentially Significant Drug Interactions

Table 6 provides the effect on concentrations of VIRACEPT or concomitant drug as a result of coadministration with VIRACEPT. These recommendations are based on either drug interaction studies or predicted interactions due to the expected magnitude of interaction and potential for serious adverse events or loss of efficacy.

Table 6: Established and Other Potentially Significant Drug Interactions: Alteration in Dose or Regimen May Be Recommended Based on Drug Interaction Studies [see Clinical Pharmacology (12.3) (Tables 12 and 13) for magnitude of interaction]

Concomitant Drug Class:
Drug Name		Effect on
Concentration		Clinical Comment
HIV Antiviral Agents: Reverse Transcriptase Inhibitors

Delavirdine

↑ nelfinavir (Cmin)
↓ delavirdine

Concentrations of nelfinavir were increased while concentrations of delavirdine were decreased when the two agents were coadministered. Appropriate doses of the combination, with respect to safety and efficacy, have not been established.

Nevirapine

↓ nelfinavir (Cmin)

Concentrations of nelfinavir were decreased when coadministered with nevirapine. An appropriate dose of nelfinavir with respect to safety and efficacy has not been established.

Didanosine

↔ nelfinavir

There was no change in nelfinavir concentration when coadministered with didanosine. However, it is recommended that didanosine be administered on an empty stomach; therefore, didanosine should be given one hour before or two hours after VIRACEPT (given with food).

HIV Antiviral Agents: Protease Inhibitors

Indinavir

↑ nelfinavir
↑ indinavir

Concentrations of both indinavir and nelfinavir were increased when the two agents were coadministered. Appropriate doses for these combinations, with respect to safety and efficacy, have not been established.

Ritonavir

↑ nelfinavir
↔ ritonavir

Concentrations of nelfinavir were increased when coadministered with ritonavir. An appropriate dose of nelfinavir for this combination, with respect to safety and efficacy, has not been established.

Saquinavir

↑ nelfinavir
↑ saquinavir

Concentrations of both saquinavir and nelfinavir were increased when the two agents were coadministered. Appropriate doses for these combinations, with respect to safety and efficacy, have not been established.

ANTICOAGULANT

Warfarin

Warfarin

Coadministration of warfarin and VIRACEPT may affect concentrations of warfarin. It is recommended that the INR (international normalized ratio) be monitored carefully during treatment with VIRACEPT, especially when commencing therapy.

ANTICONVULSANTS

Carbamazepine Phenobarbital
Phenytoin


↓ nelfinavir

↓ phenytoin

Concentrations of nelfinavir may be decreased. VIRACEPT may not be effective due to decreased nelfinavir plasma concentrations in patients taking these agents concomitantly.
Phenytoin plasma/serum concentrations should be monitored; phenytoin dose may require adjustment to compensate for altered phenytoin concentration.

ANTIDEPRESSANT

Trazodone

↑ trazodone

Concomitant use of trazodone and VIRACEPT may increase plasma concentrations of trazodone. Adverse events of nausea, dizziness, hypotension and syncope have been observed following coadministration of trazodone and ritonavir. If trazodone is used with a CYP3A4 inhibitor such as VIRACEPT, the combination should be used with caution and a lower dose of trazodone should be considered.

ANTIGOUT

Colchicine

↑ colchicines

Patients with renal or hepatic impairment should not be given colchicine with VIRACEPT due to the risk of colchicine toxicity.

Treatment of gout flares –
co- administration of colchicine in patients on VIRACEPT:

0.6 mg (1 tablet) × 1 dose, followed by 0.3 mg (half tablet) 1 hour later. Dose to be repeated no earlier than 3 days.

Prophylaxis of gout-flares –
coadministration of colchicine in patients on VIRACEPT:

If the original colchicine regimen was 0.6 mg twice a day, the regimen should be adjusted to 0.3 mg once a day.
If the original colchicine regimen was 0.6 mg once a day, the regimen should be adjusted to 0.3 mg once every other day.

Treatment of familial Mediterranean fever (FMF)– coadministration of colchicine in patients on VIRACEPT:

Maximum daily dose of 0.6 mg (may be given as 0.3 mg twice a day).

ANTIMYCOBACTERIAL

Rifabutin

↑ rifabutin
↓ nelfinavir
  (750 mg TID)
↔ nelfinavir
  (1250 mg BID)

It is recommended that the dose of rifabutin be reduced to one-half the usual dose when administered with VIRACEPT; 1250 mg BID is the preferred dose of VIRACEPT when coadministered with rifabutin.

ENDOTHELIN RECEPTOR ANTAGONIST

Bosentan

↑ bosentan

Concentrations of bosentan may be increased when coadministered with VIRACEPT. Coadministration of bosentan in patients on VIRACEPT or coadministration of VIRACEPT in patients on bosentan:
Start at or adjust bosentan to 62.5 mg once daily or every other day based upon individual tolerability.

HMG-CoA REDUCTASE INHIBITORS

Atorvastatin
Rosuvastatin

↑ atorvastatin
↑ rosuvastatin

Titrate atorvastatin dose carefully and use the lowest necessary dose; do not exceed atorvastatin 40 mg/day.

IMMUNOSUPPRESSANTS

Cyclosporine
Tacrolimus
Sirolimus

↑ immuno-suppressants
↑ nelfinavir

Concentrations of these immunosuppressants and nelfinavir may be increased by coadministration of these agents with nelfinavir.

INHALED BETA AGONIST

Salmeterol

↑ salmeterol

Concurrent administration of salmeterol with VIRACEPT is not recommended. The combination may result in increased risk of cardiovascular adverse events associated with salmeterol, including QT prolongation, palpitations and sinus tachycardia.

INHALED/NASAL STEROID

Fluticasone

↑ fluticasone

Concomitant use of fluticasone propionate and VIRACEPT may increase plasma concentrations of fluticasone propionate. Use with caution. Consider alternatives to fluticasone propionate, particularly for long-term use.

MACROLIDE ANTIBIOTIC

Azithromycin

↑ azithromycin

Dose adjustment of azithromycin is not recommended, but close monitoring for known side effects such as liver enzyme abnormalities and hearing impairment is warranted.

NARCOTIC ANALGESIC

Methadone

↓ methadone

Concentrations of methadone were decreased when coadministered with VIRACEPT. Dosage of methadone may need to be increased when coadministered with VIRACEPT.

HORMONAL CONTRACEPTIVES

Ethinyl estradiol
Norethindrone

↓ ethinyl estradiol
↓ norethindrone

Concentrations of ethinyl estradiol and norethindrone were decreased when coadministered with VIRACEPT. Alternative or additional contraceptive measures should be used when oral contraceptives containing ethinyl estradiol or norethindrone and VIRACEPT are coadministered.

PDE5 INHIBITORS

Sildenafil
Vardenafil
Tadalafil

↑ PDE5 Inhibitors

Concomitant use of PDE5 inhibitors and VIRACEPT should be undertaken with caution.

May result in an increase in PDE5 inhibitor-associated adverse events, including hypotension, syncope, visual disturbances, and priapism.

Use of PDE5 inhibitors for pulmonary arterial hypertension (PAH):

• Use of sildenafil (REVATIO) is contraindicated when used for the treatment of pulmonary arterial hypertension (PAH) [see Contraindications (4)].

• The following dose adjustments are recommended for use of tadalafil (ADCIRCA™) with VIRACEPT:

Coadministration of ADCIRCA in patients on VIRACEPT or coadministration of VIRACEPT in patients on ADCIRCA:

Start at or adjust ADCIRCA to 20 mg once daily. Increase to 40 mg once daily based upon individual tolerability.

Use of PDE5 inhibitors for erectile dysfunction:

Sildenafil at a single dose not exceeding 25 mg in 48 hours, vardenafil at a single dose not exceeding 2.5 mg in 24 hours, or tadalafil at a single dose not exceeding 10 mg dose in 72 hours, is recommended. Use with increased monitoring for adverse events.

PROTON PUMP INHIBITORS

Omeprazole

↓ nelfinavir

Omeprazole decreases the plasma concentrations of nelfinavir. Concomitant use of proton pump inhibitors and VIRACEPT may lead to a loss of virologic response and development of resistance.

ANTIPSYCHOTICS

Quetiapine

↑ quetiapine

Initiation of VIRACEPT in patients taking quetiapine:
Consider alternative antiretroviral therapy to avoid increases in quetiapine drug exposures. If coadministration is necessary, reduce the quetiapine dose to 1/6 of the current dose and monitor for quetiapine-associated adverse reactions. Refer to the quetiapine prescribing information for recommendations on adverse reaction monitoring.

Initiation of quetiapine in patients taking VIRACEPT:
Refer to the quetiapine prescribing information for initial dosing and titration of quetiapine.
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