Trick of the Trade
Interestingly, there are minimal systemic effects with oral naloxone. So, constipation can be directly targeted without causing systemic opioid withdrawal. Published case series reports show a variable range of therapeutic doses, ranging from 0.1-20 mg of oral naloxone. One series quoted no effectiveness under 1.5 mg. Generally 2 mg PO is a good starting point. Then titrate up slowly to achieve the laxative effect to minimize any systemic absorption.
FYI, you need to use the IV preparation, because no PO formulation exists.
Alternatively per Bryan Hayes (@PharmERToxGuy), you can also use methylnaltrexone, which also is a mu-receptor antagonist. It is dosed 8-12 mg (0.15 mg/kg) subcutaneously.
Thanks to Dr. Graham Walker (Kaiser San Francisco) and Sarah Burkart (PA at Univ of Cincinnati) for sharing this great tip!
Holzer P. Non-analgesic effects of opioids: Management of opioid-induced constipation by peripheral opioid receptor antagonists: prevention or withdrawal? Curr Pharm Des. 2012 Jun 28. [Epub ahead of print] Pubmed