Health care products giant Johnson & Johnson on Thursday blamed loan payments in Argentina for a 23.2 percent dip in earnings despite a 16.1 percent rise in sales for the first quarter of 1990. Earnings for the period were $244 million, or 73 cents per share, on sales of $2.84 billion, compared with $317 million, or 95 cents per share, on sales of $2.45 billion for the same period a year ago. The latest results were reduced by a nonrecurring charge of $125 million resulting from paying off an Argentine subsidiary's loan that was growing rapidly because of inflation in that country. Excluding the nonrecurring costs, the company said its earnings would have risen 16.4 percent. ``We are very pleased with the 16 percent increase in sales, especially in the light of the extreme competitive environment in the domestic consumer environment,'' Johnson & Johnson Chairman Ralph S. Larsen said in a statement. ``The increase reflects substantial sales gains from worldwide and professional operations, as well as strong international revenues from our Consumer businesses,'' he said. Larsen said sales of six key products, including a blood screening product for Hepatitis C, increased substantially in the quarter. Johnson & Johnson is the world's largest manufacturer of health care products serving consumer, pharmaceutical and professional markets. It reported 1989 sales of $9.76 billion.