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.

Sunitinib (Sutent - Pfizer) and sorafenib (Nexavar - Bayer), two oral tyrosine kinase inhibitors, have been approved by the FDA for treatment of advanced renal cell carcinoma (RCC). Sunitinib is also approved for use in patients with gastrointestinal stromal tumor (GIST) who are not responding to or are intolerant of standard therapy with imatinib (Gleevec).

The FDA has announced changes in the labeling of simvastatin to reduce the risk of myopathy. These changes include limiting the use of the 80-mg maximum dose to patients who have been taking it for 12 months or more without evidence of myopathy and new recommendations for use of simvastatin with other drugs. Simvastatin is available alone (Zocor, and others) and in combination with ezetimibe (Vytorin) and with niacin (Simcor).

A recent letter to the editor of the Annals of Internal Medicine documented a single case of myopathy apparently due to an interaction between simvastatin (Zocor, and others) and green tea. Since it became available generically, simvastatin has surpassed atorvastatin (Lipitor) as the best selling statin. As such, it is probably the most common cause of statin-induced myopathy, which is often a result of drug interactions.

The tables in this article list drugs used for treatment of cancer in the USA and Canada and their major adverse effects. The choice of drugs in Table I is based on the opinions of Medical Letter consultants. Some drugs are listed for indications for which they have not been approved by the US Food and Drug Administration. In some cases, such as elderly patients or those with many co-morbid illnesses, the regimen of choice might not be suitable. For many of the cancers listed, surgery and/or radiation therapy may be the treatment of choice or may also be part of the management. Anticancer...

Sildenafil (Viagra), tadalafil (Cialis) and vardenafil (Levitra, Staxyn) have become the standard treatment for erectile dysfunction. Head-to-head comparisons of these agents are still lacking, but some differences between them and new recommendations for their dosing (see Table 2) are worth noting.

Aprepitant (Emend - Merck), the first substance P/neurokinin 1 (NK₁) receptor antagonist to be approved by the FDA, is now available for oral use with corticosteroids and selective serotonin (5-HT₃) receptor antagonists to prevent nausea and vomiting caused by highly emetogenic anticancer drugs such as cisplatin.

The centuries-old anti-inflammatory drug colchicine (Colcrys, and others) is FDA-approved for prophylaxis and treatment of gout flares and for treatment of familial Mediterranean fever. It is also used off-label to treat pericarditis, and in recent years has been investigated for reduction of cardiovascular risk in patients with coronary artery disease (CAD).

Artesunate for injection (Amivas LLC), a semi-synthetic artemisinin derivative, is now approved by the FDA for initial (induction) treatment of severe malaria in children and adults. It has been available from the CDC on a compassionate use basis since 2007. Artemether/lumefantrine (Coartem), another artemisinin-based drug, was approved earlier for oral treatment of uncomplicated Plasmodium falciparum malaria. IV artesunate is now the only FDA-approved injectable antimalarial drug available in the US; IV quinidine has been discontinued.