Question:

Dear guys,

I wonder if I can combine over the counter cream called Chap.Ice (contains Camphor and Phenol) with Zovirax cream for the treatment of cold sore.

I know that Chap.Ice is just for symptomatic relief while Zovirax eliminate the underlying cause.

If it is possible to combine, how should I use both medication?

Answer:

If I were you, I wouldn’t do this. Here’s why.

Drug delivery through the skin is a pretty complicated science. Getting the right mix of ingredients to get the drug in the right solubility state isn’t easy, and the drug company making Zovirax had to do a lot of work to get their formula just right. Then they had to test it on humans to make sure their formula successfully delivered the acyclovir, the main ingredient in Zovirax, to its site of action.

I was one of the doctors who helped do some of those studies. One of the rules for our patients was they not use other lip products. So we didn’t test what happens when Zovirax and Chap.Ice are used together. There’s a small chance that nothing unusual happens, and the acyclovir still gets delivered appropriately. There’s a small chance that more drug gets delivered, maybe if the blood flow to the lip is increased by the camphor and phenol, or if camphor and phenol soften up the lip surface so more acyclovir can get in. There’s a large chance that less drug would get delivered, because the ingredients of the Chap.Ice could add an extra barrier over the lips, or they could change the solubility of the acyclovir in the Zovirax, or maybe the phenol would react with the acyclovir. Really, there are lots of ways the Chap.Ice might interfere with the work of the Zovirax.

So, while it might seem convenient to combine the two products, it’s probably best not to do so.

For more information:

Go to the Pharmacy and Medications health topic.