benzocaine and lidocaine

Andy,

Is benzocaine and/or lidocaine a potential risk for:

1) thalassemia minor?

2) thalassemia intermetia (where you have higher than usual quantities of hg F)?

3) thalassemia major?

Is it possible that it could induce a methemoglobinemia in any of these instances?

This concern was introduced to me today - I understand that these drugs are commonly used in medical and dental procedures.  Even emla can become an issue if this is truly a concern for thalassemia. 

Thank you kindly,

Sharmin

I posed this question to the docs in Oakland.  i was told that it is not a concern for thal majors because the amount of hemoglobin f is very low in these individuals.  I am waiting to hear if it is a concern for thal minors.  I guess it would be helpful for us to all have this information on hand were we to require any medical procedures. 

Sharmin

As per Oakland - there isn't a risk for thal minors or majors.  I suspect that because thal intermedias have significantly higher fetal hemoglobin that they be aware of this possible risk. 

Sharmin

Thanks Sharmin
aabha

The FDA has advised against the use of teething gels that contain benzocaine due to the risk of methemoglobinemia, a blood disorder where iron in hemoglobin changes from the oxygen carrying ferrous state to the ferric state, which can't transport oxygen. As the percentage of this HbM increases past 1%, a serious and potentially fatal condition can develop. There are also many recorded cases of methemoglobinemia being caused by liberal use of benzocaine and lidocaine sprays while intubating awake patients. Emla cream contains lidocaine and it is important to stress that this is a prescription drug and should be used only as directed. Do not use more than the specified dose. Use of benzocaine cream over a wide body area resulted in methemoglobinemia in a beta dominant minor. Fetal hemoglobin is more easily affected.

The best advice is to minimize the use of benzocaine and to use Emla only as directed. These drugs can pose a risk to the general population and the thal population is no exception and those with higher levels of fetal hemoglobin may be at higher risk. My opinion is that doctors should be made aware of any blood disorder that may be present before the use of these sprays that are used to numb the throat before breathing or stomach tubes are placed.

Andy,

Does this relate mostly to benzocaine or lidocaine as well? And is it most relevant with respect to intubation or other uses as well?  Dentists commonly use lidocaine and it is used as an aneasthetic for certain surgeries I believe.

Thanks again,

Sharmin

Concerning lidocaine in Emla cream, see the post at http://www.thalassemiapatientsandfriends.com/index.php/topic,132.msg710.html#msg710
There are very specific instructions for use of this drug and the should be closely followed. The cream should be used in only the specified quantity and should not be rubbed into the skin. Emla is a very useful drug for those using desferal, but it must be respected as a drug.
Lidocaine spray can also induce methemoglobinemia. In most all reported cases involving the spray, this has been caused by a too liberal use of these anesthetic sprays. These are used anytime a breathing or stomach tube is placed. This induced methemoglobinemia and this can be fatal even when treated quickly. With all of these products, misuse can result in tragedy.