Patent ID: 8642641

Claim:
A co-crystal comprising a pyrrolidinone having the formula (I) wherein R 1 is a C 1 -C 6 alkyl group; R 2 is a C 1 -C 6 alkyl group which is optionally substituted by 1 to 3 halogens or R 2 is a C 2 -C 6 alkenyl group; and one or more salts selected of the group consisting of MgCl 2 , MgSO 4 , MgBr 2 , Mg 3 (PO4) 2 , MgHPO4, Mg(H 2 PO 4 ) 2 , MgCO 3 , Mg(HCO 3 ) 2 , CaCl 2 , CaSO 4 , CaBr 2 , CaCO 3 , Mg(HCO 3 ) 2 , Ca 3 (PO4) 2 , CaHPO4, Ca(H 2 PO 4 ) 2 , KCl, KBr, K 2 SO 4 , KHSO 4 , K 2 CO 3 , K 2 HPO 4 , KH 2 PO 4 , K 3 PO 4 , NaCl, NaBr, Na 2 SO 4 , Na 2 CO 3 , Na 2 HPO 4 , NaH 2 PO 4 , Na 3 PO 4 , NH 4 Cl, NH 4 Br, (NH 4 ) 2 SO 4 , (NH 4 ) 2 CO 3 , (NH 4 ) 2 HPO 4 , NH 4 H 2 PO 4 , Na 3 PO 4 and their hydrates, or a magnesium, calcium, potassium, sodium, or ammonium salt of malic acid, maleic acid, citric acid, pamoic acid, acetic acid, lactic acid, fumaric acid, methyl sulfonic acid, mesylic acid, or ascorbic acid.