People Drug Stores Inc. reported yesterday a 15 percent jump in profits for the quarter ended Jan. 20 as sales increased 10 1/2 percent.

Washington Gas Light Co., Washington Homes and M. S. Ginn and Co. also reported improved earnings.

Profits for Peoples, the largest retail drug chain on the East Coast, totaled $2.8 million (77 cents a share) in the recent quarter compared with $2.4 million (67 cents) a year ago. Sales were $143 million compared with $130 million.

Chairman A. C. Israel and President Sheldon Fantle said yesterday that the first-quarter gains reflect "growing and continuing benefits of our major revitalization actions," which have included merchandise reorganizations and face lifts for many Peoples' stores.

"It is important to keep in mind that first-quarter results include the Christmas season, typically our most profitable selling period... this period is not representative of subsequent quarters," they cautioned.

Under the names of Reed, Lee, Health Mart, Lane and Peoples, the Alexandria firm operates 382 retail stores in mid-Atlantic and southeastern states.

Washington Gas Light Co., in a regular monthly earnings statement, said earnings increased for the 12 months ended Jan. 31 compared with a year ago. However the gain, which reflects higher natural gas consumption as colder winter weather set in, did not result in a level of profitability permitted by area regulatory agencies.

Net income rose to $13 million ($2.33 a share) from $12.5 million ($2.20) as revenues rose by $32 million to $354 million, Washington Gas reported. Natural gas sales rose although there were 1,776 fewer meters in service at the end of January compared with the 1978 period.

Washington Homes Inc., a home builder based in Oxon Hill, reported higher earnings and sales for the quarter and six months ended Jan. 31. For the recent three months, profits were $79,026 (6 cents a share) compared with $16,194 (1 cent) a year ago, and sales rose to $7.7 million from $7.2 million.

Six-month earnings were up sharply to $372,478 (30 cents) from $87,000 (7 cents) as sales rose to $19.2 million from $15.4 million. Directors voted to omit a quarterly dividend for the recent three months. Washington Homes last paid 2 1/2 cents a share in June.

M. S. Ginn and Co., a Hyattsvillebased office products distributor, reported record profits of $584,181 (81 cents a share) in the six months ended Dec. 31 compared with $539,868 (75 cents) a year ago. Sales rose to $22 million from $18.7 million.

Ginn directors voted a cash payout of 6 cents a share payable March 30 to owners of record March 14.