Astra Zeneca Ltd has changed the ampoule tops for Naropin (ropivacaine) Polyamp 2mg/ml, 7.5mg/ml and 10mg/ml and Marcain (bupivacaine) Polyamp 0.25 per cent, 0.375 per cent, 0.5 per cent and 0.75 per cent, from "rock-off" tops to "twist-off" tops. The company says that the formulations and prices remain the same.