Functional constipation, known as chronic idiopathic constipation (CIC), is constipation that does not have a physical (anatomical) or physiological (hormonal or other body chemistry) cause. It may have a neurological, psychological or psychosomatic cause. A person with functional constipation may be healthy, yet has difficulty defecating. Symptoms and diagnosis
Chronic idiopathic constipation is similar to constipation-predominant irritable bowel syndrome (IBS-C); however, people with CIC do not have other symptoms of IBS, such as abdominal pain. Diagnosing CIC can be difficult as other syndromes must be ruled out as there is no physiological cause for CIC. Doctors will typically look for other symptoms, such as blood in stool, weight loss, low blood count, or other symptoms. To be considered functional constipation, symptoms must be present at least a fourth of the time. Possible causes are:

Anismus
Descending perineum syndrome
Other inability or unwillingness to control the external anal sphincter, which normally is under voluntary control
A poor diet
An unwillingness to defecate
Nervous reactions, including prolonged and/or chronic stress and anxiety, that close the internal anal sphincter, a muscle that is not under voluntary control
Deeper psychosomatic disorders which sometimes affect digestion and the absorption of water in the colonThere is also possibility of presentation with other comorbid symptoms such as headache, especially in children. Treatment
Treatment options appear similar and include prucalopride, lubiprostone, linaclotide, tegaserod, velusetrag, elobixibat, bisacodyl, sodium picosulphate, and most recently, plecanatide.
Zanamivir, a transition-state analogue inhibitor of neuraminidase, was the result.In 1999, the product was approved for marketing in the US and Europe for treatment of influenza A and B. The FDA advisory committee had recommended by a vote 13 to 4 that it should not be approved, because it lacked efficacy and was no more effective than placebo when the patients were on other drugs such as paracetamol. But the FDA leadership overruled the committee and criticised its reviewer, biostatistician Michael Elashoff. The review of oseltamivir, which was also in approval process  at that time, was taken away from him, and reassigned to someone else. In 2006 zanamivir was approved in the US and Europe for prevention of influenza A and B.

References
External links
Drug Information: Zanamivir Inhalation MedlinePlus drug