Methylnaltrexone bromide for the treatment of opioid-induced constipation.

INTRODUCTION: The extensive and alarming use of opioids for pain management in patients with chronic pain receiving palliative care is associated with non-tolerable gastrointestinal (GI) adverse effects. Opioid-induced constipation (OIC) is the most common adverse effect impairing patient quality of life (QOL). In addition, OIC is one of the treatment limiting consequences of opioid analgesics. Management of OIC is becoming a challenge since traditional laxatives have limited efficiency. Peripherally acting mu-opioid receptor antagonists (PAMORA) have been developed for the treatment of OIC with methylnaltrexone bromide being the first approved to treat OIC in adults with advanced illness undergoing palliative care. Areas covered: The authors systematically review the clinical evidence for methylnaltrexone bromide including a review of the pharmacokinetic and pharmacodynamic data along with clinical effectiveness and cost-effectiveness. Though there is a need for further long-term clinical investigation, there is a large body of evidence for both its efficacy and safety in the treatment of OIC. Expert opinion: Methylnaltrexone has both subcutaneous injection and oral dosage forms available in the market. The lack of more evidence in specific populations such as pregnant women, pediatrics and elderly still remains. The global consumption of methylnaltrexone shows a projection of increased use since its approval worldwide in 2008.