Comparison of Pain Tolerance between Opioid Dependent Patients on Methadone Maintenance Therapy (MMT) and Opioid Naive Individuals.
OBJECTIVE
This study compared pain sensitivity among opioid dependent patients on methadone maintenance therapy (MMT) and opioid naive subjects.


METHODS
The three hundred participants comprised 152 opioid naive subjects and 148 opioid dependent patients. Opioid naive subjects had not taken any opioids including morphine and methadone to their best knowledge and were presumed so after two consecutive negative urine screenings for drugs. All opioid dependent patients were stabilized in treatment, defined as having been enrolled in the program for more than one month with no change of methadone dosage over the past one month. Excluded from the study were individuals with chronic or ongoing acute pain and individuals with a history of analgesics ingestion within 3 d before the cold pressor test (CPT). Pain tolerance to CPT was evaluated at 0 h, and at 2, 4, 8, 12, and 24 h post-methadone dose.


RESULTS
Patients exhibited a significantly shorter mean pain tolerance time of 34.17 s (95% CI 24.86, 43.49) versus 61.36 (52.23, 70.48) [p < 0.001] compared with opioid naive subjects. Time-dependent mean pain tolerance was also significantly different when naive subjects were compared to patients (p = 0.016).


CONCLUSIONS
This study revealed hyperalgesia amongst patients on MMT, as manifested by their quicker hand withdrawal. The complaints of pain in this population should not be underestimated and the pain should be evaluated seriously and managed aggressively.
Department of Pharmacy, Hospital Universiti Sains Malaysia, Kelantan, Malaysia. Pharmacogenetics and Novel Therapeutics Cluster, Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia (USM), Kelantan, Malaysia.
Zalina
Z
Zahari
Chee Siong
CS
Lee
Muslih Abdulkarim
MA
Ibrahim
Nurfadhlina
N
Musa
Mohd Azhar
MA
Mohd Yasin
Yeong Yeh
YY
Lee
Soo Choon
SC
Tan
Nasir
N
Mohamad
Rusli
R
Ismail
D000293:Adolescent; D000328:Adult; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D004361:Drug Tolerance; D005260:Female; D006801:Humans; D008297:Male; D008691:Methadone / Q000494:pharmacology* / Q000627:therapeutic use*; D008875:Middle Aged; D009293:Opioid-Related Disorders / Q000188:drug therapy*; D017288:Pain Threshold / Q000187:drug effects*; D055815:Young Adult
D000701:Analgesics, Opioid; D008691:Methadone