International Bank of Washington yesterday reported a 19 percent increase in profits for 1979, including an 89 percent increase in fourth-quarter profits.

The bank said 1979 profits were $18.5 million ($2.53 a share) compared with 1978 profits of $15.6 million ($2.15), and fourth-quarter profits rose from $3.1 million (41 cents) to $5.8 million (79 cents). International Bank said the fourth-quarter increase was due to elimination of a $2 million reserve in a bank in Lebanon.

The bank also reported 1979 revenues of $26 million, up from $21.4 million in 1978 and fourth-quarter revenues of $7.6 million, up from $4.3 million.

International Bank, with operations in all states and 38 foreign countries, reported stockholders equity of $164.5 million, which the bank said is the largest of any nongovernmental financial institution in the Washington area.

Potomat Electric Power Co. yesterday reported profits of $11.7 million (22 cents a share) for the two months ending Feb. 29, a 30 percent jump over profits of $8.2 million (15 cents) for the same period last year.

Pepco also said revenues for the two-month period jumped to $116.8 million from $113.4 million last year. For the 12 months ending on Feb. 29, Pepco reported profits of $87.7 million, more than $11 million above year-ago profits for the same 12 months.