The withdrawal of two generic competitors to heart drug Toprol XL helped AstraZeneca boost second quarter sales and raise full-year earnings targets.Anglo-Swedish firm Astra posted a 9% increase in sales at constant exchange rates (CER) to $7.96bn. Pre-tax profit for the three months to 30 June rose 14% to $2.6bn and core profit leapt 32% to $3.4bn.The drug maker toasted strong growth of Toprol-XL in the US following the withdrawal of generic products. It accounted for 3% of global sales at CER.Core earnings jumped 37% to $1.64 a share, prompting a rise in the full-year target to between $5.70 and $6, up from $5.15-5.45 previously."Our business performance, in the context of tough global economic conditions, has been better than we anticipated," said chief executive David Brennan.Astra said the increased earnings guidance is due solely to operational performance, with no help from currency moves.A first interim dividend of 59 cents is an increase of 7% on a year ago.