There are several types of medication errors.
When a drug is available in more than one dosage forms, there is the potential for error.
For example verapamil is a medication often used to lower blood pressure or to treat cardiac arrhythmias (abnormal heart beats).
It is available in many strengths from several manufacturers.
The problem arises with the 120mg strength.
There is an immediate release (the tablet releases the drug relatively quickly) and an extended release (the tablet releases the drug slowly over a period of time) tablet of 120 mg verapamil.
The extended release (ER) tablet will provide the drug slowly over a 24 hour period but the immediate release tablet provide all the medication at the same time.
Once released, a medication has limited time in the body.
In this cases about 8 hours.
The immediate release tablet must be given every 8 hours to maintain its effectiveness.
The real problem happens when the intended product is the extended release tablet but the prescription is written or phoned in to the pharmacy as verapamil 120mg tablets, take 1 tablet daily instead of verapamil ER 120mg tablets, take 1 tablet daily.
What happens is the patient would get all 120 mg of the verapamil in the first couple hours (essentially an over-dose) and the balance of the day there would not be enough medication in the body to control blood pressure.
I have personally seen this error in the pharmacy and in the hospital.
The problem is compounded by the fact that the verapamil ER 120mg tablet is often for people who do not need a lot of medication to do the job whereas the verapamil 120 immediate release tablet is for those requiring a large dose (360mg per day).
This error could cause severe decreases in blood pressure or dangerous decreases in heart rates.
Another example is Effexor 75 mg and Effexor XR 75 mg.
The regular Effexor (venlafaxine) is intended to be given 2 to 3 times daily but the Effexor XR 75mg releases slowly over 24 hours so it should be given only once daily.
The problem occurs when the prescription reads Effexor 75 mg once daily instead of Effexor XR 75mg once daily The order is for the regular product and not the XR.
According to the Effexor package insert there is a small increase in the possibility of seizures with the regular over the Effexor XR.
Even though this is a small chance it is still a concern and this error can be prevented.
My last example is Wellbutrin (bupropion).
This drug comes in three different dosage forms.
There is a regular formula for dosing 3 times daily, an SR formula for twice daily dosing and an XL formula for once daily dosing.
The presence of 3 different formulas can become confusing as errors can happen as in the examples above plus the potential of the prescriber to mix up the formulas and request an XR product by accident.
There are many drugs with the potential for this type of error.
In addition to the possibility of errors with these extended release products, there is no standards for the use of a suffix on drug names.
Suffixes CD, CR, ER, LA, SR, XL, XR do not have a standard definition describing the dosage form or the release characteristics of the product.
There are steps you can take to protect yourself from these types of errors.

• Ask the doctor about the medication prescribed, if it is extended release, how often to take it, and what it is to be used for.
  
• Make sure you can read the prescription and it agrees with what the doctor told you.
  
• Be aware if your medication is available in more than one dosage form and verify you are receiving the correct one.
  
• Check the bottle from the pharmacy to verify it is the same as what the doctor wrote.
  
• Always question any changes in the size, shape or color of the medication you receive.
  

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