More than 60% of antibiotic prescriptions are for broad-spectrum varieties, and are useless 25% of the time because they were prescribed for viruses, a study found, and they are more often for respiratory problems, skin infections and urinary tract infections.
The study appeared online July 29 in the Journal of Antimicrobial Chemotherapy.
Researchers drew their conclusions after reviewing a public database with information on ambulatory care visits at physician offices and hospital-based outpatient and emergency departments from 2007 to 2009. Among nearly 240,000 adult visits in which an antibiotic was prescribed, broad-spectrum agents were 61% and narrow spectrum agents were 39%.
The most commonly prescribed antibiotics were quinolones (25%), macrolides (20%) and aminopenicillins (12%), and they were most commonly prescribed for respiratory conditions (41%), skin/mucosal conditions (18%) and urinary tract infections (9%).
Researchers also noted that broad-spectrum agents were more likely to be prescribed for respiratory infections such as bronchitis, during emergency department visits, and for patients ages 60 and older.
Researchers estimate there was an average of 985 million annual ambulatory care visits from 2007 to 2009, with antibiotics being prescribed in an estimated 101 million of those visits each year, or 62 million broad-spectrum prescriptions
Uncertainty about the cause of an infection is one factor in the overuse of broad-spectrum antibiotics, the authors noted, but physicians may also believe that their patients expect an antibiotic if they take the time to see the doctor, the researchers noted.