An extended release pharmaceutical dosage form comprising an active pharmaceutical ingredient and a release modifying excipient, the release modifying excipient comprising: 35% to 95% (wt/wt) of a high amylose starch, 1% to 40% (wt/wt) of a cross-linked hydroxypropylated amylopectin, and1% to 30% (wt/wt) of a pre-gelatinized common starch, wherein the release modifying excipient is substantially free of crosslinks between amylose and amylopectin subunits and substantially free of crosslinks between amylose and amylose subunits, optionally wherein: (i) the release modifying excipient comprises: 55% to 65% (wt/wt) of the high amylose starch, 30% to 40% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 1% to 10% (wt/wt) of the pre-gelatinized common starch; (ii) the release modifying excipient comprises: 65% to 75% (wt/wt) of the high amylose starch, 1% to 10% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 20% to 30% (wt/wt) of the pre-gelatinized common starch; (iii) the release modifying excipient comprises: 70% to 80% (wt/wt) of the high amylose starch, 10% to 20% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 5% to 15% (wt/wt) of the pre-gelatinized common starch; or (iv) wherein the release modifying excipient comprises: 85% to 95% (wt/wt) of the high amylose starch, 1% to 10% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 1% to 10% (wt/wt) of the pre-gelatinized common starch. 35% to 95% (wt/wt) of a high amylose starch, 1% to 40% (wt/wt) of a cross-linked hydroxypropylated amylopectin, and1% to 30% (wt/wt) of a pre-gelatinized common starch, wherein the release modifying excipient is substantially free of crosslinks between amylose and amylopectin subunits and substantially free of crosslinks between amylose and amylose subunits, optionally wherein: (i) the release modifying excipient comprises: 55% to 65% (wt/wt) of the high amylose starch, 30% to 40% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 1% to 10% (wt/wt) of the pre-gelatinized common starch; (ii) the release modifying excipient comprises: 65% to 75% (wt/wt) of the high amylose starch, 1% to 10% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 20% to 30% (wt/wt) of the pre-gelatinized common starch; (iii) the release modifying excipient comprises: 70% to 80% (wt/wt) of the high amylose starch, 10% to 20% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 5% to 15% (wt/wt) of the pre-gelatinized common starch; or (iv) wherein the release modifying excipient comprises: 85% to 95% (wt/wt) of the high amylose starch, 1% to 10% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 1% to 10% (wt/wt) of the pre-gelatinized common starch. (i) the release modifying excipient comprises: 55% to 65% (wt/wt) of the high amylose starch, 30% to 40% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 1% to 10% (wt/wt) of the pre-gelatinized common starch; 55% to 65% (wt/wt) of the high amylose starch, 30% to 40% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 1% to 10% (wt/wt) of the pre-gelatinized common starch; (ii) the release modifying excipient comprises: 65% to 75% (wt/wt) of the high amylose starch, 1% to 10% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 20% to 30% (wt/wt) of the pre-gelatinized common starch; 65% to 75% (wt/wt) of the high amylose starch, 1% to 10% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 20% to 30% (wt/wt) of the pre-gelatinized common starch; (iii) the release modifying excipient comprises: 70% to 80% (wt/wt) of the high amylose starch, 10% to 20% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 5% to 15% (wt/wt) of the pre-gelatinized common starch; or 70% to 80% (wt/wt) of the high amylose starch, 10% to 20% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 5% to 15% (wt/wt) of the pre-gelatinized common starch; or (iv) wherein the release modifying excipient comprises: 85% to 95% (wt/wt) of the high amylose starch, 1% to 10% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 1% to 10% (wt/wt) of the pre-gelatinized common starch. 85% to 95% (wt/wt) of the high amylose starch, 1% to 10% (wt/wt) of the cross-linked hydroxypropylated amylopectin, and 1% to 10% (wt/wt) of the pre-gelatinized common starch.