Comprehensive Care Corp. reported that its earnings dropped 13% for the second quarter ended Nov. 30, to $2.1 million from the previous year's second-quarter earnings of $2.5 million. The company said its second-quarter earnings were affected by a charge to pretax earnings of about $500,000 for costs related to the initial public offering of stock in its RehabCare subsidiary. That offering has been delayed indefinitely because of the decline in the stock market. Contrasted with the second quarter of fiscal 1987, revenues increased 10%, to $50.2 million from $45.5 million. For the first six months of fiscal 1988, the Irvine-based provider of drug and alcohol abuse treatment programs posted net income of $4.6 million, compared with $7.2 million a year earlier. Revenues totaled $100.5 million, up from $96.1 million for the first half of fiscal 1987. B. Lee Karns, chairman and president, also announced that the company plans to repurchase up to 1 million shares of its common stock. Purchases will be made from time to time in the open market or in negotiated transactions.