Two patients (patients 1 and 3) had catheters placed in contrast enhancing brain. The dialysate AUCs increased slightly by 10.0 and 19.1% when temozolomide was administered with regadenoson. For patient 1, brain AUC increased from 4.4 to 5.4 µg/ml h with temozolomide alone to combination with regadenoson, respectively. And for patient 3, brain AUC increased from 3.2 to 4.2 µg/ml h with temozolomide alone to combination with regadenoson, respectively. Generally, treatment with regadenoson exhibited a quicker rise to peak concentration but failed to demonstrate a prolonged increase of brain interstitial temozolomide concentrations (Fig. 2). The variations in peak time, Tmax and AUC can be seen in individual patient neuropharmacokinetics with temozolomide alone vs. temozolomide + regadenoson (Fig. 3, Additional file 1: Table S1).Fig. 3Maximum temozolomide concentration (Cmax) and area under the curve (AUC). Cmax of contrast enhancing and non-contrast enhancing tissue (a). Brain AUC of contrast enhancing and non-contrast enhancing tissue (b). Brain:Plasma AUC of contrast enhancing and non-contrast enhancing tissue (c). Black circles represent non-contrast enhancing tissue, white circles represent contrast-enhancing tissue