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AACE Patient Safety - News

A Lethal Mistake – a misread prescription for propylthiouracil (PTU)

2008-07-16 12:13:44
By: Jeffrey R. Garber, MD, FACP, FACE

* Patient Safety Alert *

– by Jeffrey R. Garber, MD, FACP, FACE, on an FDA communication

A soon to be released FDA edition of "Drug Topics" will report that a pregnant woman with hyperthyroidism was given Purinethol (mercaptopurine) instead of propylthiouracil, which was prescribed as "PTU 50 mg tid". She had a spontaneous abortion and died following placental delivery. The autopsy revealed "marked hypoplasia of bone marrow", likely attributable to the administration of mercaptopurine¹.

Several lessons may be gleaned from this tragic event caused by a previously reported mistake²³⁴ first recognized over 25 years ago⁴.

The challenge of educating physicians about uncommon, but potentially fatal errors
The hazards of underreporting errors
The pitfalls of using abbreviations when writing prescriptions
The potential benefit of having patients check their prescriptions as well as their indications with pharmacists

Potential solutions have been proposed in the FDA’s preliminary alert to endocrinologists. These include avoiding the abbreviation “PTU” for propylthiouracil and providing its indication on prescriptions. Recommendations are forthcoming for pharmacists. These will, no doubt, be aimed at minimizing the chances of inadvertently interchanging similarly appearing 50-mg round and white pills, whose names share common letters, for one another.

Additional advice for endocrinologists and our colleagues:

Educating patients about their prescriptions
Reporting such errors – a key to heightening awareness about uncommon but potentially fatal, preventable mistakes
Minimizing the chances that written prescription are misread or misinterpreted – a leading cause of pharmacy dispensing errors – by writing clearly and or using office staff, who will write legibly and follow guidelines about abbreviations and decimal points, to help generate written prescriptions that are complete, legible, and accurate
Devising and employing an electronic prescription system, that, among other things, provides safeguards against potentially dire dispensing errors.

Dr. Egan Commentary

¹ http://www.thyroid.org/professionals/publications/news/08_07_08_notice.html

² Blum M, Peck V, Seltzer T, Goldberg-Berman J Alert: 6-mercaptopurine may be erroneously dispensed instead of propylthiouracil. Thyroid. 2005 Nov;15(11):1315

³ Is an Antithyroid or Antimetabolite Needed? Preventing Confusion Between Propylthiouracil and Purinethol. North Carolina Board of Pharmacy, Newsletter on the WEB, Jan. 2004, http://www.ncbop.org/Jan04-3.asp/.

⁴ Lin RL, Stein RJ, Schaffer MI. A Purinethol (6-mercaptopurine) fatality in a case of prescription negligence: a gas chromatographic determination of 6-mercaptopurine.J Forensic Sci. 1982 Apr; 27(2): 454-60.

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There are 3 comments

Shashank R Joshi – India

August 27, 2008 - 14:51

Subject: Byetta and Pancreatitis-Practical Issues

Byetta and Pancreatitis - An Indian View
-- Dr. Shashank R Joshi, MD, DM, FACE, FRCP(Glg)
Endocrinologist, Mumbai India
Hon Editor, Journal of The Association of Physicians of India
Chair, Indian Chapter of AACE

Both your bezoar case and pancreatopathy make good reading. Incidentally, I reviewed global literature of all agents of diabetes and their impact on the pancreas. All secretagogues, as well as glinides, have case reports of pancreatitis reported. However, cause-effect relationship has never been proven, both in animal studies as well as reported anecdotes. In fact, the global reportage of pancreatitis is so small statistically that most cases had some other etiology for pancreatic injury. So currently we do not have sufficient evidence for pancreatic injury due to exenatide, but it stands to reason that in a predisposed individual it may act as a potential trigger for pancreatic injury.

The real worry will be the ongoing LAR preparation which is now under phase 3 trial program

Exenatide has some evidence to suggest that it may trigger a cholinergic response in alcoholics and that could be a beeptive pathway for pancreatic injury

So clinically, exenatide needs the following caveats prior to its use:
1) Chronic alcoholics or abuse
2) Refractory GERD
3) History of acute or chronic pancreatitis
4) Gall stones
5) Gastroparesis

One should avoid or exercise caution to use it in the above stated indications. Our institution avoids byetta in the above mentioned indications till further data will emerge

In India to date, one case of pancreatitis is reported.

Richard Hellman MD – NKC,

August 26, 2008 - 11:06

Subject: Byetta and stomach pain

Dear J.A. Moore,

Your question about Byetta and your nightly pain, which your doctor says is from your stomach, is a very important one, and thank you for asking it. It is not clear as to whether you are free of abdominal pain at this time. If you are pain free at this time, it may be difficult to be sure as to why you had pain in the past. If you are still having nightly pain, then my comments may be more relevant. Since I am not your doctor, I do not know enough about you to make a diagnosis or offer therapy, but I hope I can be helpful in some general suggestions. As we get older, the risk that a pain in the abdomen is a serious medical condition increases. But resistant pain in the abdomen can be from many causes: infections, such as a H.Pylori infection of the stomach, inflammation, such as pancreatitis, or a disease of the intestine called Crohn's disease, motility problems, such as gastroparesis, and other possibilities, vascular problems such as abdominal aneurysms, and also tumors, such as cancers of the stomach and of the pancreas. But there are other, much more common and simple problems, such as irritability of the gastrointestinal tract either due to drugs, such as metformin, or conditions as irritable bowel syndrome. I certainly could not tell from what you have said whether your problem is any of the above, or whether it is or was related to byetta.

But I think your questions are right-on and you should find out why you have had pain and whether it has anything to do with either byetta or to metformin. Your doctor should be able to do some screening tests for pancreatitis, and gastroenterologists can answer other of your questions, but I would encourage you to proceed to ask your health providers to answer your excellent questions.

You should also note that in the editorial I wrote on byetta, I discussed the responsibility of doctors to answer questions of this type. Thank you again for your excellent question. I hope I have been helpful.

J.A. MOORE – Washington DC

August 25, 2008 - 13:47

Subject: Byette

I have been taking Byette and have a nightly pain which the Dr says is my stomach. I am overweight and have high triglycerides. The Drs ran all kinds of tests on my gall bladder xrays plus other tests....including nuclear meds test. Gall bladder tests turned up negative. Then the Gastro Drs said it must be the valve on the stomach that's weak on diabetics and they gave me some medicine that kept me going to the toliet. I quit the medicine after almost a week of torture. But I took 3-Omega Oils capsules 3 times a day and Liptor and Tricore. My lipids were tested two weeks ago and the pain is gone and my Lipids very low in normal range with one type being under the allowable rate but my Endo Dr said that was OK. SHOULD I WORRY THAT I may have or had pancreatitis? I am still taking the Byette plus Metformin and Lantus..