UPDATE 1-Airgas cuts 3rd-quarter outlook, shares fall

(Adds share price)

HOUSTON, Jan 8 (Reuters) - Airgas Inc (ARG.N), a distributor of medical and specialty gases, lowered its fiscal third-quarter profit outlook on Thursday, citing a big slowdown in sales in December.

Airgas shares fell about 3 percent to $37 in post-market trading.

Airgas, based in Radnor, Pennsylvania, now expects earnings for the quarter ended Dec. 31 of 74 cents to 76 cents per share, down from its prior forecast of 82 cents to 84 cents per share.

"We are prepared to initiate further expense reductions if the low sales volumes we saw in December persist for very long," Airgas Chairman and Chief Executive Officer Peter McCausland, said in a statement.

Analysts on average had expected Airgas to report a profit of 79 cents a share, according to Reuters Estimates. (Reporting by Anna Driver in Houston; Editing by Andre Grenon)