Family physician Mary Frank couldn't understand why one elderly man with high-blood pressure wasn't responding to his medication. She had been steadily increasing his dose, but his blood pressure remained unstable.
Finally, the man acknowledged he had been sharing his pills with his wife. He also would stop taking his medication a few days before his appointment hoping his blood pressure would be higher so that he and his wife could then split a higher-dose drug.
But the practice put the couple at risk of a stroke or heart attack. ''This is not something people should take lightly. It's truly dangerous and frustrating," said Frank of Rohnert Park, Calif.
When it comes to prescription medications, many people embrace the adage to share and share alike. Armed with good intentions and largely unaware of the dangers, they gladly hand over leftover antibiotics, asthma inhalers, antidepressants, insulin and pain pills. After all, if the drugs worked for them, then perhaps they'll help similarly suffering family members, friends or colleagues. And, considering the drugs' expense, throwing away excess, out-of-date or ineffective pills can seem like a waste.
Some consumers appear to be sharing medications out of necessity. With the costs of drugs and medical care rising, they have trouble paying for their own prescriptions or the doctor visits required to obtain them.
Although no one tracks adverse events caused by drug sharing, adverse drug reactions overall are responsible for up to 7 percent of hospital admissions.
In some circumstances, sharing drugs can be extremely dangerous because one of the people taking the drug hasn't been seen by a physician to determine if he or she indeed needed the drug, what dosage, or possible allergic reactions.
''It's possible that people are ending up in the hospital and even dying from [sharing prescriptions]," said Dr. Stephen Soumerai, director of drug policy research at Harvard Medical School.
Researchers say those most likely to share prescription drugs are the poor and the elderly, as well as family members who have a common chronic illness, such as diabetes.
''If you ask people why they are doing this, they say they have no other option," said Chien-Wen Tseng, an assistant professor at the University of Hawaii who has studied the ways people deal with rising prescription drug prices. ''To many of them, it's better than not taking the medication at all."
The risks of prescription-sharing vary dramatically depending on the user and the medication.
For example, when prescribing blood pressure medications, doctors choose from among dozens of varieties depending on the patient's weight, medical history and other diseases. Taking high blood pressure medication improperly can lead to strokes, heart attacks and heart failure.
People with diabetes, likewise, may need different drugs; some drugs can be safe for some users, but cause potentially dangerous allergic reactions in others. Those who take too little or too much of a diabetic drug can risk going into insulin shock or damage their liver. Giving antidepressants to someone who seems depressed but is actually manic-depressive can worsen the disorder.
Antibiotic-sharing not only fuels overall resistance levels to the drugs, but it can also increase the chances of a lingering individual infection. ''It's hard to convince people, but this is like driving 90 miles per hour mph in a 25-mile-per-hour zone," said Dr. Yehuda Handelsman, an endocrinologist in Tarzana, Calif.
Dozens of interviews with researchers, doctors, pharmacists and senior centers across the country suggest the problem is growing.
Moreover, the number of pills that can be shared is multiplying; almost half of Americans take a prescription drug and 17 percent take three or more. The dangers of sharing medications may be overlooked, experts say, by a public overly confident in its ability to self-medicate -- a perception amplified by the dramatic rise in direct-to-consumer pharmaceutical advertising in recent years.
When the AARP asked seniors last fall about sharing medications, about 4 percent of Medicare beneficiaries -- or nearly 1.7 million people -- said they had shared prescription medications with family and friends in the last year.
Teenagers are also likely to give and take others' medications. A report from the Centers for Disease Control and Prevention in 2003 found that 20 percent of girls and 13.4 percent of boys share medications with friends, although cost wasn't usually the motivation. Many share sleeping pills and acne medication such as Accutane, the report found. Sharing Accutane is extremely worrisome; the drug is believed to cause birth defects, and girls and women of childbearing age are supposed to take a birth-control pill while taking the medication.
The Food and Drug Administration generally forbids the redistribution of prescription drugs once they have been dispensed to consumers, but states can supplement that with their own regulations.