flip-flop without absorption information?

Dear nmusers, I'm working on the population PK of a therapeutic peptide candidate for rheumatoid arthritis. Three dose levels of the peptide were administered as a single subcutaneous injection. We have some limitations, for instance, the dataset is very sparse and is lacking in the information of the absorption phase. Some therapeutic peptides have demonstrated flip-flop PK, specially those administered by subcutaneous or intramuscular. Is it possible to evaluate the flip-flop phenomenon without absorption information? I'll appreciate all your suggestions and advice. Best, Niurys -- Niurys de Castro Suárez, PhD Assistant Professor of Pharmacometrics Associate Research Pharmacy Department Institute of Pharmacy and Food, University of Havana Cuba "Una estrella brilla en la hora de nuestro encuentro"