We thank you for your question. The random vancomycin level can certainly be drawn on the day that the patient is to receive the antibiotic. It should be noted though that if a unit has decided to measure vancomycin levels, it is presumably because that information is being used to determine when the next dose of vancomycin should be administered. If they receive the result on the same day, then they can indeed give the dose that same day.
 
The authors of the latest 2022 ISPD peritonitis guidelines do not give specific guidance on timing of drawing of Vancomycin levels for therapeutic drug monitoring for patients with PD-associated peritonitis being treated with IP Vancomycin (1, page 123). This is an area that is indeed in need of much further research (2).
 
1.Li PK, Chow KM, Cho Y, Fan S, Figueiredo AE, Harris T, Kanjanabuch T, Kim YL, Madero M, Malyszko J, Mehrotra R, Okpechi IG, Perl J, Piraino B, Runnegar N, Teitelbaum I, Wong JK, Yu X, Johnson DW. ISPD peritonitis guideline recommendations: 2022 update on prevention and treatment. Peritoneal Dialysis International. 2022 Mar;42(2):110-153. Available at: https://journals.sagepub.com/doi/pdf/10.1177/08968608221080586
 
2.Lam E, Lien YT, Kraft WK, Piraino B, Vozmediano V, Schmidt S, Zhang J. Vancomycin in peritoneal dialysis: Clinical pharmacology considerations in therapy. Peritoneal Dialysis International. 2020 Jul;40(4):384-93.