Is There Interaction Between Phenylephrine And Levothyroxine?

Posted on Fri, 1 Apr 2016

Medically reviewed by Ask A Doctor - 24x7 Medical Review Team

Fri, 1 Apr 2016 Answered on

Tue, 7 Jun 2016 Last reviewed on

Question : Yes, I am getting a bhronical cold and have some capsules my son bought over the counter. It is the new sudafed I believe called phenylephrine10 mg I also have tussin liquid is it ok to take these to help the congestion that is beginning. I am 81 years old and weigh 170 lbs.

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Answered by Dr. Bonnie Berger-Durnbaugh (21 minutes later)

Brief Answer:
Yes, these are ok to take:

Detailed Answer:
Hello and welcome,

I'm sorry you are getting sick. Yes, these medications are ok to take together. There is a mild risk for phenylephrine to interact with the levothyroxine, possibly increasing blood pressure slightly. Otherwise no other interactions to watch for with

Phenylephrine
Tussin (guaifenesin)
Levothyroxine
Sertraline
Aspirin

For the Tussin to work well, drink plenty of water which will help it thin secretions.

Phenylephrine is a milder form of decongestant than Pseudoephedrine, which is what Sudafed used to be. It is still possible to buy Pseudoephedrine but it is kept behind the pharmacist's counter so that illegal drug manufacturers don't buy it up and "cook" it into illegal drugs.

Please let me know if I can provide further information or clarification. Hope you are feeling better soon!

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar