The role of methadone in pain treatment in cancer patients

Methadone belongs to step 3 opioid analgesics of the World Health Organization (WHO) analgesic ladder. Methadone is most frequently used in cancer pain when fentanyl, buprenorphine, morphine and oxycodone fail or cause severe adverse effects. Less frequently methadone is considered as a first strong opioid with more frequent use as an addition to other opioids when analgesia is unsatisfactory.

Methadone displays specific pharmacodynamic and pharmacokinetic properties comparing to other opioids. Methadone advantages include multimode analgesia and suggested high efficacy in neuropathic pain, high oral and rectal bioavailability, long-lasting analgesia, lack of active metabolites, excretion mainly with faeces and low cost. Methadone disadvantages are difficult to predict, long and changeable plasma half – life which may lead to accumulation and adverse effects, metabolism through cytochrome P-450, which may lead to many drug interactions, possibility of QT interval prolongation, difficulties in establishing equianalgesic dose ratio with other opioids and methadone dosing. The mentioned advantages of methadone, especially high analgesic efficacy, low cost of the treatment and lack of significant immunosupressive effect causes that methadone is an important alternative or complement to other opioids. However, methadone treatment should be provided by physicians experienced in chronic pain therapy.

In the article basic pharmacodynamic and pharmacokinetic properties of methadone, equianalgesic dose ratio calculation with other opioids and methadone dosing guidelines were described. A review of clinical studies of methadone in cancer pain patients was performed. On the base of literature review and own experience equianalgesic dose ratio of other opioids and methadone dosing guidelines were proposed.