What's the best otc remedy for post nasal drip and cough? i tried mucinex (guaifenesin) dm and it did very little to help my coughing and throat "tickle" sensation.

Depends: If the cough is from post-nasal drips, it may respond to OTC nasal steroid (takes a few days). It is from sinusitis, you may need a Rx antibiotic. If from asthma, you will need a Rx controller drug for asthma. Each condition requires difficult treatment and thus a diagnosis is needed.

Try generic Claritin (loratadine): A nonsedating antihistamine like Claritin, (loratadine) Zyrtec or Allegra may do the trick. They are over-the-counter and the generic is just fine