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.

With the deployment of hundreds of thousands of troops in Saudi Arabia, health problems endemic to the Arabian Peninsula may be coming to the attention of physicians in the USA and other areas.

The FDA recently announced that it will permit reintroduction of alosetron hydrochloride (Lotronex - GlaxoSmithKline) for treatment of irritable bowel syndrome (IBS). The drug was previously withdrawn from the market because of severe gastrointestinal toxicity. The reintroduced drug will have a 50% lower starting dose, a narrower indication and some other marketing restrictions (www.fda.gov/cder/drug/infopage/lotronex/lotronex.htm).

Rifaximin (Xifaxan – Salix), a minimally absorbed oral antibiotic approved previously to treat travelers' diarrhea and to reduce the risk of recurrent hepatic encephalopathy, has now been approved by the FDA for treatment of irritable bowel syndrome with diarrhea (IBS-D). Eluxadoline (Viberzi – Actavis), a mu-opioid receptor agonist, was also recently approved for IBS-D and will be reviewed in a future issue.

Rifaximin (Xifaxan - Salix), a non-absorbed oral antibiotic derived from rifampin (Rifadin, and others), has been approved by the FDA for treatment of travelers' diarrhea caused by noninvasive strains of Escherichia coli in patients 12 years of age or older. It has been available in Europe since 1987.

Erlotinib (Tarceva) is the second oral epidermal growth factor receptor (EGFR) inhibitor to become available in the US for treatment of advanced refractory NSCLC. In clinical trials, erlotinib produced a response rate of only 8.9%, but increased median survival from 4.7 to 6.7 months. Patients who had never smoked and those with EGFR-positive tumors survived longer. Erlotinib is generally well tolerated; diarrhea and rash are the most common adverse effects.

Irinotecan hydrochloride (Camptosar - Pharmacia & Upjohn; formerly CPT-11) has been approved by the US Food and Drug Administration for treatment of metastatic colorectal cancer refractory to other drugs including fluorouracil (5-FU; Adrucil and others).

A reader asked whether healthcare providers should avoid prescribing the angiotensin receptor blocker (ARB) olmesartan medoxomil (Benicar, and others) because it can cause severe GI adverse effects.In 2013, the FDA warned that olmesartan can cause sprue-like enteropathy, a condition characterized by intestinal villous atrophy, severe chronic diarrhea, and significant unintended weight loss. The warning was based on 23 cases of serious sprue-like enteropathy associated with use of olmesartan, some occurring years after starting the drug. All patients improved after stopping olmesartan; 10 had a...

View the Expanded Table: Antibiotics for Travelers' Diarrhea

The oral tyrosine kinase inhibitor neratinib (Nerlynx – Puma Biotechnology) has been approved by the FDA for use in combination with capecitabine (Xeloda, and generics) for treatment of advanced or metastatic human epidermal growth factor receptor 2 (HER2)-positive breast cancer in adults who received ≥2 prior anti-HER2-based regimens for metastatic disease. It was previously approved for use as monotherapy for extended adjuvant treatment of adults with early-stage, HER2-positive breast cancer following adjuvant trastuzumab (Herceptin)-based therapy. HER2 is overexpressed in...