Disclaimer: The materials provided below are infomational and should not be relied upon as legal advice. I am licensed in California and the materials below are based on California law.
If you know of a pending class action lawsuit, you should contact the attorneys to see if you would qualify to join the class. Otherwise, you may need to retain your own attorney and start a separate lawsuit. You should consult your own attorney in your own jurisdiction to help protect your legal rights.
I am unaware of any class action filed in any state or federal court against the maker of trazodone. I believe your friend is mistaken. You can always file your own lawsuit (individually or on behalf of a putative class) to recover damages for injuries proximately caused by taking trazodone. I recommend that you contact your local state or county bar association for a referral to an attorney who may be able to assist you.