Clinical evaluation of the efficacy of methylnaltrexone in resolving constipation induced by different opioid subtypes combined with laboratory analysis of immunomodulatory and antiangiogenic effects of methylnaltrexone

Table 1 Opioid characteristics regarding constipation

Opioid	Receptor affinity	Lipophilicity	Distribution site	Incidence of constipation¹
Morphine Sulphate	Mainly μ, some κ	Low	Peripheral	60% (range 21-70%)
Oxycodone	μ, κ and δ	Intermediate	Central and peripheral	65% (range 25-74%)
Fentanyl	μ (highly selective)	High	Central	35% (range 10-55%)

¹Estimated incidence of constipation without laxative use and the range of this incidence found in different studies in which a proportion of patients already uses laxatives.

ISSN: 1472-684X