据悉，迄今为止尚无治疗IBS-C的处方药，因此Amitiza成为美国首个获批的此类药物。肠易激综合征（IBS）的临床表现为痉挛、腹痛、胃胀、便秘和腹泻，会导致患者不适和苦恼，且女性的发病率是男性的两倍。

    FDA药品评审中心主任介绍说，IBS使某些患者失去参加日常活动的能力，Amitiza的问世将有助于缓解症状。Amitiza常见的副作用包括恶心、腹泻和腹痛，其他罕见的副作用有尿路感染、口干、昏厥、外周性水肿、呼吸困难和心悸。Amitiza的用法为每日两次，必须和水和食物一起服用。医生和患者应定期评估是否有继续服用的必要。

    此外，Amitiza不适合儿童和男性患者使用，严重腹泻和确诊或疑似肠梗阻患者禁用。肝肾功能不全患者、孕妇或哺乳期妇女其安全性尚不明确。Amitiza此前曾被批准用于治疗慢性特发性便秘，但剂量更高，每天用量为24毫克。

Amitiza™ (lubiprostone)

A new treatment for chronic idiopathic constipation
Many patients with chronic constipation often attempt treating their symptoms with traditional over-the-counter products (e.g. fiber, bulking agents, laxatives) or lifestyle changes. In many cases, these therapies do not adequately address all patients’ symptoms. Amitiza™ (lubiprostone), indicated for chronic idiopathic constipation in adults, is the first medication that locally targets the activation of intestinal chloride channels to help regulate fluid balance and improve symptoms associated with chronic idiopathic constipation.1

Amitiza improves chronic idiopathic constipation symptoms through activation of chloride channels
Many symptoms that patients experience with chronic constipation (see box below) occur because their bodies are unable to maintain a balance of fluid within the intestinal tract, thus limiting the passage of stool. Amitiza helps regulate this fluid imbalance through activation of chloride channels, which transport chloride ions into the intestinal tract. Once the chloride ions are transported, sodium and water passively follow into the intestinal tract through a change in the electrical balance and a more appropriate distribution of fluid is achieved. The end result is an increase in the passage of stool and improved chronic idiopathic constipation symptoms.1

In efficacy studies, Amitiza has shown to increase the frequency of spontaneous bowel movements (SBMs) by up to 54% and 83% (5.4 and 5.3 mean SBM per week) in two pivotal trials after four weeks compared to placebo (3.5 and 2.9 mean SBM per week).3 Also, in these two trials, 57% and 63% (n=242) of patients on Amitiza had an SBM within 24 hours of starting therapy compared to 37% and 32% (n=132) with placebo.3 These increases in SBM translate into a decrease in constipation symptoms, including abdominal bloating, abdominal discomfort, stool consistency, and straining.3

Amitiza is taken twice daily with food
The recommended daily dose of Amitiza is 24-mcg twice daily with food.4 Clinical trials have demonstrated symptom improvement for up to 12 months, but pharmacists should periodically recommend that patients assess the need for continued therapy with their physician.3 Amitiza is available as a 24-mcg small gelatin capsule.4

Symptoms of Chronic Constipation2 •  Infrequent stools •  Difficult stool passage, including straining, sensation of incomplete evacuation, hard or lumpy stools, prolonged time to defecation, and the need for manual maneuvers •  Symptoms persist for any three or more of the previous 12 months

* Relief is defined as $ 3 spontaneous bowel movements per week

Facts about Constipation •  Constipation is one of the most common digestive complaints, affecting up to 28 million adults in the United States5 •  Constipation is the cause of 2.5 million physician visits and 92,000 hospitalizations annually6 •  More than twice as many women are affected than men5

Important Safety Information
•	Amitiza is indicated for the treatment of chronic idiopathic constipation in the adult population.
•	Amitiza should not be used in patients with a known hypersensitivity to any components of the formulation and in patients with a history of mechanical gastrointestinal obstruction. Patients with symptoms suggestive of mechanical gastrointestinal obstruction should be evaluated prior to initiating Amitiza treatment.
•	The safety of Amitiza in pregnancy has not been evaluated in humans. In guinea pigs, lubiprostone has been shown to have the potential to cause fetal loss. Amitiza should be used during pregnancy only if the benefit justifies the potential risk to the fetus. Women who could become pregnant should have a negative pregnancy test prior to beginning therapy with Amitiza and should be capable of complying with effective contraceptive measures.
•	Amitiza should not be administered to patients that have severe diarrhea. Patients should be aware of the possible occurrence of diarrhea during treatment. If the diarrhea becomes severe, patients should consult their health professional.
•	In clinical trials, the most common adverse event was nausea (31%). Other adverse events ($5% of patients) included diarrhea (13%), headache (13%), abdominal distention (7%), abdominal pain (7%), flatulence (6%), sinusitis (5%) and vomiting (5%).
Pharmacist Counseling Tips
•	If patients experience severe diarrhea, pharmacists should instruct them to contact their physician immediately.
•	Although Amitiza is not a laxative, it has been shown to work quickly. Many patients in clinical trials experienced a bowel movement within 24 hours of starting therapy.3
•	Because the safety of Amitiza has not been evaluated in pregnancy, pharmacists should inform women who become pregnant during therapy to contact their physician to discuss the risks and benefits of continuing treatment. Pharmacists should also discuss maintaining an adequate method of birth control with female patients of childbearing potential.
•	Although Amitiza indirectly affects sodium and fluid transport in the intestinal tract, it has not been shown to cause electrolyte abnormalities in the bloodstream.4