I was desperately trying to get rid of my extremely painful
Caugh and took 300mg of tessalon and now I'm feeling worse. I know it was a dumb move but now I'm afraid I'm having a bad reaction... should I go to the ER asap

Please seek medical attention as soon as possible.

Tessalon which is the trade name though call " Benzonatate " .

Benzonatate is a non-narcotic oral cough suppressant, or antitussive, with effects that last from 6 to 8 hours. Since it is not an opioid, benzonatate is not as prone to abuse like some other cough medications such as codeine.

Anyway it is generally sold in Yellow or Blue 100mg or 200mg softgel capsules.

You start at for most people 100mg, three times a day.

Due to its potency and potential toxicity, the capsules must be swallowed intact in order to allow slower release of the medication.

If you have taken 300mg of it at once , I would be going to a Doctor / medical practitioner A.S.A.P. as you maybe experiencing an overdose.

See below and have someone else drive you, if you have any of these.

Reported side effects include drowsiness, dizziness, and dysphagia. There are numerous reports of death related to overdose of benzonatate, mostly in children.