The primary objective of this trial is to evaluate the efficacy and safety of electroacupuncture in the management of opioid-induced constipation in patients with cancer.

Inclusion Criteria:

1. Diagnosis of OIC based on the Rome IV Criteria: Participants must meet the following criteria for OIC: Constipation or worsening of constipation symptoms during opioid use or dose changes, with at least two of the following symptoms: 1. at least 25% of bowel movements are labored; 2. at least 25% of bowel movements are dry ball or hard stools; 3. at least 25% of bowel movements are incomplete; 4. at least 25% of bowel movements have anal rectal obstruction and/or blockage in at least 25% of the bowel movements; 5. at least 25% of the bowel movements required manual assistance (e.g., finger-assisted defecation, pelvic floor support); 6. less than 3 bowel movements per week; (2) the rare occurrence of loose stools when laxatives were not used.
2. Rare occurrence of loose stools without the use of laxatives;
3. History of OIC symptoms for at least 1 week prior to enrollment;
4. Age: Participants must be aged between 18 and 85 years;
5. Cancer Status: Participants must have stable cancer with a life expectancy of greater than 6 months;
6. ECOG Performance Status: Participants must have an Eastern Cooperative Oncology Group (ECOG) performance status of 0-3;
7. Stable Opioid Maintenance: Participants must have been receiving a relatively stable opioid regimen for at least 2 weeks prior to screening, with a daily morphine equivalent dose (MED) ranging from 30 mg to 1000 mg. Additionally, opioid treatment is expected to continue for at least 10 weeks;
8. Bowel Movement Frequency: In the absence of laxative use, participants must have fewer than two spontaneous bowel movements (SBMs) per week;
9. Ability to Take Oral Medications: Participants must be capable of swallowing oral medications, food, and beverages;
10. Informed Consent: Participants must voluntarily consent to participate in the trial and provide signed informed consent;
11. Exclusion of Gastrointestinal Motility Agents: Participants must not have used any gastrointestinal motility-promoting drugs within 1 week prior to randomization.

Exclusion Criteria:

1. Significant Bowel Dysfunction due to Gastrointestinal or Other Structural Abnormalities: Participants diagnosed with clinically significant bowel dysfunction resulting from gastrointestinal or related structural abnormalities (excluding OIC), such as inflammatory bowel disease, rectal prolapse, gastrointestinal obstruction, peritoneal metastases, or peritoneal tumors;
2. Recent History of Abdominal Surgery: Participants with a history of gastrointestinal or abdominal surgery, or abdominal adhesions within 1 month prior to screening; or a history of bowel obstruction within 3 months prior to screening;
3. Active Gastrointestinal Conditions: Diagnosis of active diverticular disease, severe hemorrhoids, anal fissures, or artificial rectum or anus;
4. Presence of Abdominal Catheters or Feeding Tubes: Participants with abdominal catheters or feeding tubes in place;
5. Pelvic Diseases Affecting Bowel Transit: Participants diagnosed with pelvic diseases known to significantly affect bowel transit (e.g., ≥2nd degree uterine prolapse, uterine fibroids ≥5 cm located in the posterior uterus);
6. Recent or Planned Chemotherapy: Participants who received a new chemotherapy regimen within 14 days of screening, or who plan to receive such treatment during the study period;
7. Recent or Planned Radiotherapy: Participants who received radiotherapy within 28 days prior to screening, or who plan to undergo radiotherapy during the study period;
8. Recent Gastrointestinal Surgery or Interventions: Participants who have undergone or are scheduled to undergo surgeries or interventions within 28 days of screening that could significantly affect gastrointestinal function or are expected to prevent completion of the trial;
9. Uncontrolled Medical Conditions: Participants with uncontrolled hyperthyroidism, severe hypertension, cardiovascular disease, systemic infections, or coagulation disorders (e.g., hypercoagulability or bleeding tendencies);
10. Excessive Use of Opioids Due to Acute Pain: Participants who have required more than four additional doses of opioid analgesics per day for more than 3 consecutive days during the baseline period due to acute pain, or those who have modified their opioid maintenance regimen during this period;
11. Severe Cancer Pain Unresponsive to Opioids: Participants who experience severe cancer-related pain despite standard opioid therapy (e.g., average daily pain intensity of 7-10 on the Numerical Rating Scale [NRS], where 0 is "no pain" and 10 is "the worst pain possible");
12. History of Opioid Discontinuation Due to Severe Adverse Events: Participants with a history of opioid discontinuation due to severe adverse events, or those expected to discontinue opioid use due to potential risks of adverse events;
13. Recent Use of Opioid Antagonists: Participants who have received opioid receptor antagonists within 1 month prior to screening;
14. Inability to Provide Informed Consent: Participants who are unconscious, psychotic, or unable to express subjective symptoms. (As acupuncture is an invasive procedure requiring 30 minutes per session, such participants will be excluded for safety reasons.);
15. Bleeding Disorders: Participants with bleeding disorders, as acupuncture involves skin penetration, and individuals with bleeding tendencies are at increased risk of complications;
16. Recent Acupuncture Treatment: Participants who have received acupuncture treatment within 3 months prior to screening;
17. Participation in Other Clinical Trials: Participants who have participated in or are currently participating in another clinical trial within the past 3 months;
18. Other Medical or Treatment Conditions: Any other participants deemed by the investigator to be unsuitable for the study due to concomitant treatments or medical findings.

Due to the specific nature of acupuncture clinical research, it is difficult to accomplish double blinding of subjects and operators, so this trial was blinded to subjects, outcome assessors, and statisticians only. To assess the success of blinding, all patients who received acupuncture were asked to guess their group allocation five minutes after the completion of treatment.