Drug of the Month: 4 Things You Should Know About Amitiza

by Alan Rook, PharmaD, Clinical Pharmacist
Ashton Hamilton, PharmD candidate

1. What is Amitiza®?

Amitiza (lubiprostone), manufactured by Takeda Pharmaceuticals Inc., is FDA approved for opioid-induced constipation in patients with chronic non-cancer related pain. It works by activating chloride channels in the intestines—which promotes fluid secretion in addition to assisting with passing of the stool.

2. How is Amitiza available?

Amitiza is available as an oral capsule, and it comes in 8 mcg and 24 mcg capsules. Usual dosing for opioid-induced constipation is a 24 mcg capsule, taken twice daily. Amitiza is a brand drug, and there is currently no generic equivalent.

3. Are There Therapeutic Alternatives?

There are various therapeutic alternatives for this medication. The patient can use a step therapy approach by starting with an osmotic laxative. If that does not provide the necessary therapeutic effect, it can be followed by the addition or substitution of a stimulant laxative—or an opioid antagonist if laxatives are not sufficient.  However, if there is no response with the previous options, the patient may be prescribed Amitiza. Stool softeners have shown to have no additional therapeutic benefit.

• Osmotic laxatives are generally well tolerated and cause less cramping than stimulant laxatives. The patient may choose from MiraLAX® (polyethylene glycol) or lactulose. The usual dose for MiraLAX is 17 g of powder dissolved in 4-8 ounces of a beverage, once daily. The maximum recommended duration of treatment is two weeks. Lactulose is dosed 10-20 g orally, once daily for 24-48 hours.

• Common side effects of osmotic laxatives include abdominal bloating, cramping, diarrhea, flatulence, and nausea.

• Stimulant laxatives increase the rate of gastrointestinal motility and secretions. The patient may choose from Dulcolax® (bisacodyl) or Senokot® (senna). The usual dose for Dulcolax is 5-15 mg orally—once daily, or a 10 mg rectal suppository—once daily. Use of Dulcolax for more than 7 days is not recommended. Senna should be dosed 17.2 mg sennosides (2 tablets) orally—once daily.

• Common side effects of stimulant laxatives include abdominal colic, abdominal discomfort, diarrhea, and proctitis (with suppository use).

4. AWP Pricing for Amitiza vs. Other Options*

The Average Wholesale Price (AWP) of Amitiza is $6.29 per 8 mcg and 24 mcg capsule. The medication is dosed two times daily, requiring 60 tablets per month, making the AWP for a 30-day supply $377.40.

The osmotic laxatives are a much cheaper starting option. For a 30-day supply of MiraLAX, the AWP is $22.44. For a 30-day supply with a daily dose of 10 g of lactulose, the AWP is $21.90. The most cost effective option for an osmotic laxative is lactulose.

The stimulant laxatives are also cost effective. For a 30-day supply of a daily dose of 5 mg of Dulcolax, the AWP is $3.60. On the other hand, the AWP of a 30-day supply of Senokot is $17.40. The most cost effective option for a stimulant laxative is Dulcolax.

This month’s bonus: Movantik®

Movantik® (naloxegol) is an opioid antagonist that is also FDA approved for opioid-induced constipation in patients with chronic non-cancer related pain. Prior to administration, it is recommended that all laxatives be discontinued. If the patient has a suboptimal response to this drug, laxatives may be resumed after 3 days.

For a 30-day supply with a daily dose of 25 mg of Movantik, the AWP is $299.40, which is slightly more cost effective than Amitiza. Although the two drugs may have similar costs, the mechanism of action is slightly different. Since Movantik is composed of naloxone conjugated with a polyethylene glycol polymer, the drug cannot cross the blood brain barrier. This allows Movantik to function in the gastrointestinal tract, thus decreasing the patient’s constipation. As a final point, this alternative drug is recommended for its lower costs and increased patient compliance with once daily administration.

* AWP figures mentioned throughout the article may vary slightly depending on the manufacturer.