The FDA has approved belatacept (bel at´ a sept; Nulojix – Bristol-Myers Squibb) for prevention of organ rejection in adult patients receiving a kidney transplant.

Tacrolimus (Prograf - Fujisawa), previously called FK506 (Medical Letter, 33:94, 1991), has been approved by the US Food and Drug Administration for primary prevention of organ rejection in patients receiving liver transplants. The drug has also been used as rescue therapy for organ graft rejection unresponsive to cyclosporine (Sandimmune) and other immunosuppressive drugs.

The B-lymphocyte stimulator (BLyS)-specific inhibitor belimumab (Benlysta – GSK), which was approved earlier for treatment of active, autoantibody-positive, nonrenal, systemic lupus erythematosus (SLE), has now been approved for use in addition to standard therapy for treatment of active lupus nephritis in adults. Belimumab is the first drug to be approved in the US for treatment of both SLE and lupus nephritis.

Itraconazole (Sporanox - Janssen), an oral antifungal triazole that has been available in the USA since 1992 for treatment of deep fungal infections (Medical Letter, 35:7, 1993), is now being marketed for treatment of dermatophyte infections of the toenails, with or without fingernail involvement.

Tacrolimus ointment (Protopic) has been approved by the FDA in 0.03% and 0.1% formulations for treatment of atopic dermatitis. Tacrolimus is used systemically (Prograf) to prevent rejection of organ transplants.

The ability of grapefruit juice to increase serum concentrations of drugs was first discovered during a study of the effect of ethanol on felodipine (Plendil) pharmacokinetics. Double-strength grapefruit juice used to disguise the taste of ethanol resulted in higher than expected serum concentrations of felodipine (DG Bailey et al, Clin Invest Med 1989; 12:357).

Sirolimus, whlch is structurally related to tacrolimus, has been approved by the FDA for prevention of acute renal transplant rejection. The manufacturer recommends that sirolimus be taken with cyclosporine and corticosteroids.

Serious adverse interactions between drugs continue to be reported. Many of these are due to inhibition or induction of cytochrome P450 (CYP) enzymes, particularly CYP3A4. CYP3A is thought to be involved in the metabolism of more than 50 percent of currently prescribed drugs.2 CYP3A4, which is more abundantly expressed than CYP3A5, accounts for most CYP3A activity in vivo.

Voclosporin (Lupkynis – Aurinia), an oral calcineurin inhibitor, has been approved by the FDA for use in combination with the antimetabolite immunosuppressant mycophenolate mofetil (Cellcept, and generics) and a corticosteroid for treatment of adults with active lupus nephritis. It is the first calcineurin inhibitor to be approved in the US for this indication. Tacrolimus (Prograf, and others) and cyclosporine (Neoral, and others), the other available systemic calcineurin inhibitors, are approved for prophylaxis of organ rejection in transplant patients.

Changes caused by one drug in the absorption, distribution, metabolism or excretion of another may lead to a pharmacokinetic adverse drug interaction (DN Juurlink et al, JAMA 2003; 289:1652). Additive drug interactions, such as vasodilation caused by both sildenafil (Viagra) and nitrates, can also have adverse effects.