A useful therapeutic or prophylactic concentration will vary from condition to condition and in certain instances may vary with {HEAD ~ the severity} of {TAIL ~ the condition} being treated and the patients susceptibility to treatment 
of
A useful therapeutic or prophylactic concentration will vary from condition to condition and in certain instances may vary with { HEAD ~ the severity } of { TAIL ~ the condition } being treated and the patients susceptibility to treatment
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH