negative time values

I wonder if there are particular reasons behind NONMEM not allowing for negative values in time, noticing that Monolix and Berkeley Madonna accept them. Are there algorithmic constraints that prevent handling of time less than 0 or is this just a plausibility check that could be lifted (in a future release)? It seems obvious that negative times can be useful, for example if there are sequential pre-treatment measurements and the convention that treatment starts at time 0. Thanks for shedding some light on this. Best regards from (c)old Switzerland, Andreas -- Andreas Krause, PhD Director, Lead Scientist Modeling and Simulation Department of Clinical Pharmacology Actelion Pharmaceuticals Ltd. • Gewerbestrasse 16 • CH-4123 Allschwil • Switzerland G06.05.W.16.2 [email protected] • www.actelion.com Address for visitors: Hegenheimermattweg 95 -- The information of this email and in any file transmitted with it is strictly confidential and may be legally privileged. It is intended solely for the addressee. If you are not the intended recipient, any copying, distribution or any other use of this email is prohibited and may be unlawful. In such case, you should please notify the sender immediately and destroy this email. The content of this email is not legally binding unless confirmed by letter. Any views expressed in this message are those of the individual sender, except where the message states otherwise and the sender is authorised to state them to be the views of the sender's company. For further information about Actelion please see our website at http://www.actelion.com