In patients who have been receiving ritonavir for at least 10 days, start bosentan at 62.5 mg once daily or every other day based upon individual tolerability

Co-administration of ritonavir in patients on bosentan:

Discontinue use of bosentan at least 36 hours prior to initiation of ritonavir.

After at least 10 days following the initiation of ritonavir, resume bosentan at 62.5 mg once daily or every other day based upon individual tolerability.
HMG-CoA Reductase Inhibitor:
atorvastatin
rosuvastatin
↑ atorvastatin
↑ rosuvastatin Use the lowest possible dose of atorvastatin or rosuvastatin with careful monitoring or consider other HMG-CoA reductase inhibitors such as pravastatin or fluvastatin in combination with NORVIR.
Immunosuppressants:
cyclosporine, tacrolimus, sirolimus (rapamycin) ↑ immunosuppressants Therapeutic concentration monitoring is recommended for immunosuppressant agents when co-administered with ritonavir.
Inhaled Steroid: Fluticasone ↑ fluticasone Concomitant use of fluticasone propionate and NORVIR increases plasma concentrations of fluticasone propionate, resulting in significantly reduced serum cortisol concentrations. Co-administration of fluticasone propionate and NORVIR is not recommended unless the potential benefit to the patient outweighs the risk of systemic corticosteroid side effects.
Long-acting beta-adrenoceptor agonist:
salmeterol ↑ salmeterol Concurrent administration of salmeterol and ritonavir is not recommended. The combination may result in increased risk of cardiovascular adverse events associated with salmeterol, including QT prolongation, palpitations and sinus tachycardia.
Narcotic Analgesic:
methadone ↓ methadone Dosage increase of methadone may be considered.
Neuroleptics:
perphenazine, risperidone, thioridazine ↑ neuroleptics A dose decrease may be needed for these drugs when co-administered with ritonavir.
Oral Contraceptives or Patch Contraceptives:
ethinyl estradiol ↓ ethinyl estradiol A pharmacokinetic study demonstrated that the concomitant administration of ritonavir 500 mg q. 12h. and a fixed-combination oral contraceptive resulted in reductions of the ethinyl estradiol mean Cmax and mean AUC by 32% and 40%, respectively. Alternate methods of contraception should be considered.
PDE5 Inhibitors:
sildenafil,
tadalafil,
vardenafil ↑ sildenafil
↑ tadalafil
↑ vardenafil Particular caution should be used when prescribing sildenafil, tadalafil or vardenafil in patients receiving ritonavir. Co-administration of ritonavir with these drugs is expected to substantially increase their concentrations and may result in an increase in PDE5 inhibitor associated adverse events, including hypotension, syncope, visual changes, and prolonged erection.

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

Sildenafil (Revatio®) is contraindicated when used for the treatment of pulmonary arterial hypertension (PAH) because a saf