Bank One said yesterday it is taking some strong medicine to get its house in order. The First USA unit reported a net loss of $379 million, a decrease of $718 million from the year-ago quarter. Earnings were affected primarily by impairment-related asset write-downs totaling $777 million pretax. Net interest income of $1.451 billion decreased $330 million, or 19%, from the year-ago quarter due to margin compression resulting from the attrition of higher priced accounts, reduced margins and lower outstandings. Compared with the first quarter, the managed delinquency rates for 30 and 90 days declined from 4.08% to 3.83% and from 1.91% to 1.69%,respectively. The managed charge-off rate declined to 5.44% from 5.78% in the prior quarter. Compared to the year-ago period, average outstandings decreased approximately 4% to $66.3 billion. At quarter-end, First USA had 54.6 million cards issued. About 826,000 new accounts were opened during the quarter. Second quarter charge volume totalled $36.8 billion. The $777 million asset write downs include: $354 million related to the value of the interest-only strip of securitized receivables; $275 million related to purchased credit card relationship intangibles; and $121 million pretax related to marketing partnership agreements. First USA also notes it realized a net gain of $46 million on the sale of its credit card operations in Canada and the UK. For complete current and historical data on Bank One/First USA visit CardData ([www.carddata.com]).