21- EXHIBIT 4.2 $125,000,000 ALPHARMA INC. 5-3/4% Convertible Notes Due 2005 REGISTRATION RIGHTS AGREEMENT March 25, 1998 SBC WARBURG DILLON READ INC. CIBC OPPENHEIMER CORP. COWEN & COMPANY c/o SBC WARBURG DILLON READ INC. 535 Madison Avenue New York,...