Eli Lilly and Amylin have asked top prescribers of their jointly-marketed diabetes treatment Byetta to limit their prescription-writing for the drug until production can be increased later this year.The fear is that UK-company Wockhardt, maker of Byetta’s container cartridge, won’t be able to manufacture the device quickly enough to keep pace with demand for Byetta. To meet the demand, the drug’s makers have enlisted the help of Bloomington, IN-based Baxter Pharmaceutical Solutions, which is expected to start producing additional Byetta cartridges during the second half of 2006. In April, Byetta sales reps stopped supplying doctors with free samples and ceased distribution of promotional materials for the drug, which saw a 40% uptick in sales this quarter. Byetta generated $68 million in first-quarter sales, up $19 million from the previous quarter. Byetta was launched in June 2005, with about 1 million prescriptions filled by 200,000 patients since.The main compound in Byetta is a synthetic derivation of a protein found in the spit of the poisonous Gila monster lizard. The formulation mimics an insulin-controlling hormone produced naturally by the human body.