The pharmacokinetic interactions listed below are
potentially clinically important. Drugs that induce hepatic enzymes
such as phenobarbital, phenytoin and rifampin may increase the clearance
of corticosteroids and may require increases in corticosteroid dose
to achieve the desired response. Drugs such as troleandomycin and
ketoconazole may inhibit the metabolism of corticosteroids and thus
decrease their clearance. Therefore, the dose of corticosteroid should
be titrated to avoid steroid toxicity. Corticosteroids may increase
the clearance of chronic high-dose aspirin. This could lead to decreased
salicylate serum levels or increase the risk of salicylate toxicity
when corticosteroid is withdrawn. Aspirin should be used cautiously
in conjunction with corticosteroids in patients suffering from hypoprothrombinemia.
The effect of corticosteroids on oral anticoagulants is variable.
There are reports of enhanced as well as diminished effects of anticoagulants
when given concurrently with corticosteroids. Therefore, coagulation
indices should be monitored to maintain the desired anticoagulant
Information for the Patient
Persons who are on immunosuppressant doses of corticosteroids
should be warned to avoid exposure to chicken pox or measles. Patients
should also be advised that if they are exposed, medical advice should
be sought without delay.