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Amitiza

"Aug. 10, 2011 -- Two studies show that a new kind of experimental medication relieves the pain and bloating of persistent constipation better than a placebo.

The studies, which are published in the New England Journal of Medicine/"...

Amitiza

Side Effects
Interactions

SIDE EFFECTS

The following adverse reactions are described below and elsewhere in labeling:

Clinical Studies Experience

Because clinical studies are conducted under widely varying conditions, adverse reaction rates observed in the clinical studies of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in practice.

During clinical development of Amitiza for CIC, OIC, and IBS-C, 1234 patients were treated with Amitiza for 6 months and 524 patients were treated for 1 year (not mutually exclusive).

Chronic Idiopathic Constipation

Adverse reactions in dose-finding, efficacy, and long-term clinical studies: The data described below reflect exposure to Amitiza 24 mcg twice daily in 1113 patients with chronic idiopathic constipation over 3-or 4-week, 6-month, and 12-month treatment periods; and from 316 patients receiving placebo over short-term exposure ( ≤ 4 weeks). The placebo population (N = 316) had a mean age of 47.8 (range 21–81) years; was 87.3% female; 80.7% Caucasian, 10.1% African American, 7.3% Hispanic, 0.9% Asian; and 11.7% elderly ( ≥ 65 years of age). Of those patients treated with Amitiza 24 mcg twice daily (N=1113), the mean age was 50.3 (range 19-86) years; 86.9% were female; 86.1% Caucasian, 7.6% African American, 4.7% Hispanic, 1.0% Asian; and 16.7% elderly ( ≥ 65 years of age). Table 1 presents data for the adverse reactions that occurred in at least 1% of patients who received Amitiza 24 mcg twice daily and that occurred more frequently with study drug than placebo.

Table 1: Percent of Patients with Adverse Reactions (Chronic Idiopathic Constipation)

System/Adverse Reaction1 Placebo
N = 316 %
Amitiza 24 mcg Twice Daily
N = 1113 %
Gastrointestinal disorders
  Nausea 3 29
  Diarrhea 1 12
  Abdominal pain 3 8
  Abdominal distension 2 6
  Flatulence 2 6
  Vomiting 0 3
  Loose stools 0 3
  Abdominal discomfort2 1 3
  Dyspepsia < 1 2
  Dry mouth < 1 1
Nervous system disorders
  Headache 5 11
  Dizziness 1 3
General disorders and site administration conditions
  Edema < 1 3
  Fatigue 1 2
  Chest discomfort/pain 0 2
Respiratory, thoracic, and mediastinal disorders
  Dyspnea 0 2
1Includes only those events associated with treatment (possibly, probably, or definitely related, as assessed by the investigator).
2This term combines “abdominal tenderness,” “abdominal rigidity,” “gastrointestinal discomfort,” “stomach discomfort”, and “abdominal discomfort.”

The most common adverse reactions (incidence > 4%) in CIC were nausea, diarrhea, headache, abdominal pain, abdominal distension, and flatulence.

Nausea: Approximately 29% of patients who received Amitiza 24 mcg twice daily experienced nausea; 4% of patients had severe nausea and 9% of patients discontinued treatment due to nausea. The rate of nausea associated with Amitiza 24 mcg twice daily was lower among male (8%) and elderly (19%) patients. No patients in the clinical studies were hospitalized due to nausea.

Diarrhea: Approximately 12% of patients who received Amitiza 24 mcg twice daily experienced diarrhea; 2% of patients had severe diarrhea and 2% of patients discontinued treatment due to diarrhea.

Electrolytes: No serious adverse reactions of electrolyte imbalance were reported in clinical studies, and no clinically significant changes were seen in serum electrolyte levels in patients receiving Amitiza.

Less common adverse reactions: The following adverse reactions (assessed by investigator as probably or definitely related to treatment) occurred in less than 1% of patients receiving Amitiza 24 mcg twice daily in clinical studies, occurred in at least two patients, and occurred more frequently in patients receiving study drug than those receiving placebo: fecal incontinence, muscle cramp, defecation urgency, frequent bowel movements, hyperhidrosis, pharyngolaryngeal pain, intestinal functional disorder, anxiety, cold sweat, constipation, cough, dysgeusia, eructation, influenza, joint swelling, myalgia, pain, syncope, tremor, decreased appetite.

Opioid-induced Constipation

Adverse reactions in efficacy and long-term clinical studies: The data described below reflect exposure to Amitiza 24 mcg twice daily in 860 patients with OIC for up to 12 months and from 632 patients receiving placebo twice daily for up to 12 weeks. The total population (N = 1492) had a mean age of 50.4 (range 20–89) years; was 62.7% female; 82.7% Caucasian, 14.2% African American, 0.8% American Indian/Alaska Native, 0.8% Asian; 5.2% were of Hispanic ethnicity; and 8.8% were elderly ( ≥ 65 years of age). Table 2 presents data for the adverse reactions that occurred in at least 1% of patients who received Amitiza 24 mcg twice daily and that occurred more frequently with study drug than placebo.

Table 2: Percent of Patients with Adverse Reactions (OIC Studies)

System/Adverse Reaction1 Placebo
N = 632 %
Amitiza 24 mcg Twice Daily
N = 860 %
Gastrointestinal disorders
  Nausea 5 11
  Diarrhea 2 8
  Abdominal pain 1 4
  Flatulence 3 4
  Abdominal distension 2 3
  Vomiting Abdominal discomfort2 2 1 3 1
Nervous system disorders
  Headache 1 2
General disorders and site administration conditions
  Peripheral edema < 1 1
1Includes only those events associated with treatment (possibly, probably, or definitely related, as assessed by the investigator).
2This term combines “abdominal tenderness,” “abdominal rigidity,” “gastrointestinal discomfort,” “stomach discomfort”, and “abdominal discomfort.”

The most common adverse reactions (incidence > 4%) in OIC were nausea and diarrhea.

Nausea: Approximately 11% of patients who received Amitiza 24 mcg twice daily experienced nausea; 1% of patients had severe nausea and 2% of patients discontinued treatment due to nausea.

Diarrhea: Approximately 8% of patients who received Amitiza 24 mcg twice daily experienced diarrhea; 2% of patients had severe diarrhea and 1% of patients discontinued treatment due to diarrhea.

Less common adverse reactions: The following adverse reactions (assessed by investigator as probably or definitely related to treatment) occurred in less than 1% of patients receiving Amitiza 24 mcg twice daily in clinical studies, occurred in at least two patients, and occurred more frequently in patients receiving study drug than those receiving placebo: fecal incontinence, blood potassium decreased.

Irritable Bowel Syndrome with Constipation

Adverse reactions in dose-finding, efficacy, and long-term clinical studies: The data described below reflect exposure to Amitiza 8 mcg twice daily in 1011 patients with IBS-C for up to 12 months and from 435 patients receiving placebo twice daily for up to 16 weeks. The total population (N = 1267) had a mean age of 46.5 (range 18–85) years; was 91.6% female; 77.5% Caucasian, 12.9% African American, 8.6% Hispanic, 0.4% Asian; and 8.0% elderly ( ≥ 65 years of age). Table 3 presents data for the adverse reactions that occurred in at least 1% of patients who received Amitiza 8 mcg twice daily and that occurred more frequently with study drug than placebo.

Table 3: Percent of Patients with Adverse Reactions (IBS-C Studies)

System/Adverse Reaction1 Placebo
N = 435 %
Amitiza 8 mcg Twice Daily
N = 1011 %
Gastrointestinal disorders
  Nausea 4 8
  Diarrhea 4 7
  Abdominal pain 5 5
  Abdominal distension 2 3
1Includes only those events associated with treatment (possibly or probably related, as assessed by the investigator).

The most common adverse reactions (incidence > 4%) in IBS-C were nausea, diarrhea, and abdominal pain.

Nausea: Approximately 8% of patients who received Amitiza 8 mcg twice daily experienced nausea; 1% of patients had severe nausea and 1% of patients discontinued treatment due to nausea.

Diarrhea: Approximately 7% of patients who received Amitiza 8 mcg twice daily experienced diarrhea; < 1% of patients had severe diarrhea and < 1% of patients discontinued treatment due to diarrhea.

Less common adverse reactions: The following adverse reactions (assessed by investigator as probably related to treatment) occurred in less than 1% of patients receiving Amitiza 8 mcg twice daily in clinical studies, occurred in at least two patients, and occurred more frequently in patients receiving study drug than those receiving placebo: dyspepsia, loose stools, vomiting, fatigue, dry mouth, edema, increased alanine aminotransferase, increased aspartate aminotransferase, constipation, eructation, gastroesophageal reflux disease, dyspnea, erythema, gastritis, increased weight, palpitations, urinary tract infection, anorexia, anxiety, depression, fecal incontinence, fibromyalgia, hard feces, lethargy, rectal hemorrhage, pollakiuria.

Postmarketing Experience

The following additional adverse reactions have been identified during post-approval use of Amitiza. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Voluntary reports of adverse reactions occurring with the use of Amitiza include the following: syncope, ischemic colitis, hypersensitivity/allergic-type reactions (including rash, swelling, and throat tightness), malaise, tachycardia, muscle cramps or muscle spasms, and asthenia.

Read the Amitiza (lubiprostone) Side Effects Center for a complete guide to possible side effects

DRUG INTERACTIONS

No in vivo drug–drug interaction studies have been performed with Amitiza.

Based upon the results of in vitro human microsome studies, there is low likelihood of pharmacokinetic drug–drug interactions. In vitro studies using human liver microsomes indicate that cytochrome P450 isoenzymes are not involved in the metabolism of lubiprostone. Further in vitro studies indicate microsomal carbonyl reductase may be involved in the extensive biotransformation of lubiprostone to the metabolite M3 [see CLINICAL PHARMACOLOGY]. Additionally, in vitro studies in human liver microsomes demonstrate that lubiprostone does not inhibit cytochrome P450 isoforms 3A4, 2D6, 1A2, 2A6, 2B6, 2C9, 2C19, or 2E1, and in vitro studies of primary cultures of human hepatocytes show no induction of cytochrome P450 isoforms 1A2, 2B6, 2C9, and 3A4 by lubiprostone. Based on the available information, no protein binding–mediated drug interactions of clinical significance are anticipated.

Interaction potential with diphenylheptane opioids (e.g. methadone): Non-clinical studies have shown opioids of the diphenylheptane chemical class (e.g., methadone) to dose-dependently reduce the activation of ClC-2 by lubiprostone in the gastrointestinal tract. There is a possibility of a dose-dependent decrease in the efficacy of Amitiza in patients using diphenylheptane opioids.

Last reviewed on RxList: 5/20/2013
This monograph has been modified to include the generic and brand name in many instances.

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