Introduction: Rectal tenesmus pain in cancer patients most frequently appears in patients with colon cancer, and as a consequence of radiotherapy of the hypogastrium region. Treatment with opioids and adjuvant analgesics is often ineffective. Patients and methods: Here, we report on two female patients diagnosed with colon and ovary cancer, respectively, who had very severe tenesmus pain (numerical rating scale 8-10) despite using high doses of opioids, including methadone with corticosteroids, anticonvulsants, antidepressants and ketamine. Results: In both patients, bupivacaine was administered via a rectal enema. In the first patient, bupivacaine was administered at a dose of 100 mg 0.1% (100 mL), and subsequently 100 mg 0.2% (50 mL), leading to effective analgesia for 8 and 12 hrs, respectively. In the second patient, 100 mg 0.1% (100 mL) was initially administered, followed by 100 mg 0.2% (50 mL), leading to effective analgesia for 12 and 17 hrs, respectively, with only dull abdominal pain reported that was relieved by 100 mg IV ketoprofen and complete disappearance of tenesmus pain. Rectal bupivacaine administration did not cause neurologic adverse effects, heart function disturbances or decreased blood pressure. A volume of 50 mL was enough to cover a painful area in the colon. Initial bupivacaine concentrations in the blood serum did not exceed 50 ng/mL and eventually dropped to 20 ng/mL and below. Conclusions: Administration of 100 mg bupivacaine as a rectal enema is safe and provides effective analgesia, and this procedure may be conducted in hospital departments and out-patient clinics. Furthermore, this procedure in the case of pain recurrence, can be repeated, and by providing effective pain relief often allows time for the patient to be transferred to a specialized pain center.