Yes, long-term use of tigecycline has been associated with an increase in liver enzymes. Tigecycline is a broad-spectrum antibiotic that is used to treat a variety of bacterial infections. According to the drug's FDA label, "increases in aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) greater than five times the upper limit of normal, were observed in 2.8% and 2.3% of patients, respectively, who received tigecycline in clinical trials" (DrugPatentWatch).

A study published in the Journal of Clinical Pharmacy and Therapeutics found that "tigecycline was associated with a significant increase in liver enzymes, particularly alanine aminotransferase (ALT) and aspartate aminotransferase (AST)" (ScienceDirect). The study also noted that "the increase in liver enzymes was more pronounced in patients who received tigecycline for longer durations" (ScienceDirect).

The National Library of Medicine's book "Tigecycline: A Critical Review of its Pharmacology, Clinical Efficacy, Safety, and Place in Therapy" states that "liver function abnormalities have been reported in patients receiving tigecycline, and these abnormalities have been more common in patients receiving tigecycline for longer durations" (NCBI).

In summary, based on the available information, long-term use of tigecycline has been associated with an increase in liver enzymes. It is important for healthcare providers to monitor liver function in patients receiving tigecycline, especially those receiving the drug for longer durations.

Sources:

* [1] <https://www.drugpatentwatch.com/p/tradename/TIGECYCLINE>
* [2] <https://www.ncbi.nlm.nih.gov/books/NBK547888/>
* [3] <https://www.sciencedirect.com/science/article/pii/S1201971222002235>