A doctor prescribed doxepin (Sinequan) 50 mg daily for a young man with depression. This medicine is available in a 50 mg capsule. But the pharmacy where the man had the prescription filled carried only 10 mg and 100 mg capsules. Sinequan treats depression and anxiety but it can also be used for other reasons. The lower dose (10 mg) is often used to treat patients with chronic itching. A higher dose (50 mg or more) is the usual dose to treat depression.
The pharmacist intended to fill the man’s prescription using the 10 mg capsules, with a label directing him to take 5 capsules daily. But when entering the prescription into the pharmacy computer, the pharmacist accidentally chose 100 mg capsules on the computer screen. Since the directions on the prescription bottle instructed the man to take 5 capsules daily, he took a total of 500 mg of doxepin every day for a month—ten times more than the prescribed dose!
The young man experienced a rapid heartbeat, headache, drowsiness, dizziness, and nausea during the month. He did not contact his doctor since he was told that he might initially experience some of these symptoms, and they would decrease over time.
The error was eventually discovered when the prescription was transferred to a different pharmacy. The pharmacist at the new pharmacy called the doctor because she was concerned about such a high dose of the medicine. (Doses for this drug should not exceed 300 mg daily.) After recognizing the error, the young man’s doctor had to slowly decrease the dose, as rapid dose changes are not recommended. The young man continued to be drowsy and fatigued for some time, even after the dose was finally adjusted to 50 mg daily.
Unfortunately, the young man had little opportunity to detect this error himself. Since doxepin was a new medicine for him, the man was not familiar with the appearance of 10 mg capsules, which look different from the 100 mg capsules. So the color and size of the capsules were not helpful clues to detecting the error. If the doctor had told the young man the dose of doxepin he was prescribing, and written it down for him, the man might have noticed the error when looking at the label on the prescription bottle. That suggestion (always leave the doctor’s office knowing what to expect at the pharmacy) was one of the messages in my blog last week.
Remember to never hesitate to contact your doctor or pharmacist if you are experiencing side effects from medicines, even if you were told to expect them. Talking to your doctor about the side effects you are experiencing might lead to the discovery of an error.
It is uncommon to need more than two or three tablets, capsules, vials, etc. in order to prepare a single dose. So an easy-to-remember safety rule for all medicines is to ask your doctor or pharmacist to double-check the dose if you need to take more than three pills, capsules, or tablets for a single dose. That might not have helped in this case, but it is another hint that perhaps the dose needs to be verified since patients should not normally be expected to swallow so many pills in order to take a single dose of any drug. This is the same advice we give to nurses who work in hospitals: if you need more than three - call the pharmacy! The implication is that something might be wrong or maybe pharmacy could do something to make it easier for the patient.
I find it unacceptable for a pharmacy to only stock one or two strengths of an item when the prescribed strength is readily available from the drug manufacturer. But even if the pharmacy does limit availability of some dosage strengths, it is still a standard dispensing practice for them to borrow or purchase a starter supply of the available strength from another pharmacy located nearby. Or, if that option isn’t available, there may be a liquid dosage form available from the medication’s manufacturer or one that the pharmacist could compound, which would make it easier for the patient to take.
Come to think of it, when choosing a pharmacy, maybe we should make it, “If you need more than two – that may be a clue.”
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