ALZA and Crescendo are developing E-TRANS fentanyl, an electrotransport system (ETS) delivery offentanyl that allows self-titration of the drug by the patient, for the potential management of acute pain. The product was previously being developed in collaboration with Janssen, but by February 2000, Janssen was no longer involved in its development. In January 1998, Janssen, ALZA and Crescendo had plans to develop the product for the potential treatment of chronic pain in addition to the acute pain indication; however, no further development for this indication has been reported since that date. ETS is able to deliver drugs that normally would not diffuse across the skin. A small electric current passes through the patient's skin, between the two electrodes on the patch. Charged drug molecules are attracted to the electrode of the opposite polarity to their own. Manipulating the charge on drug molecules is relatively easy in most instances, so the technology should be applicable to the majority of drugs that do not lend themselves to passive diffusion. ETS technology is also potentially useful in delivering rapid boluses of drug on demand. In February 2000, Merrill Lynch predicted E-TRANS fentanyl sales at US $30 million in 2002, rising to US $131 million in 2004. Analysts at SG Cowen predicted in March 2001, that E-TRANS fentanyl would be rolled out during 2003 and that sales would reach US $40 to 50 million in 2004. In April 2001, Merrill Lynch predicted earliest launch in 2003.