Despite the limited, 13-week lifespan of individual pinworms, autoinfection (infection from the original host to itself), either through the anus-to-mouth route or through retroinfection, causes the pinworms to inhabit the same host indefinitely. Life cycle
The life cycle begins with eggs being ingested. The eggs hatch in the duodenum (first part of the small intestine). The emerging pinworm larvae grow rapidly to a size of 140 to 150 micrometres, and migrate through the small intestine towards the colon. During this migration they moult twice and become adults. Females survive for 5 to 13 weeks, and males about 7 weeks. The male and female pinworms mate in the ileum (last part of the small intestine), whereafter the male pinworms usually die, and are passed out with stool. The gravid female pinworms settle in the ileum, caecum (beginning of the large intestine), appendix and ascending colon, where they attach themselves to the mucosa and ingest colonic contents. Almost the entire body of a gravid female becomes filled with eggs. The estimations of the number of eggs in a gravid female pinworm ranges from about 11,000 to 16,000. The egg-laying process begins approximately five weeks after initial ingestion of pinworm eggs by the human host. The gravid female pinworms migrate through the colon towards the rectum at a rate of 12 to 14 centimetres per hour.
The most common seen side effect of alcaftadine administration was irritation or a stinging sensation at the administration site. Pharmacokinetics
Alcaftadine is typically administrated as an eye drop which keeps its effects regional as compared to systemic effects. The main metabolite of alcaftadine is a carboxylic acid metabolite that has minimal systemic effects. The maximum concentration of its main active metabolite is 0.06 ng/ml at Tmax of 15 minutes. The minimal absorption of alcaftadine, leads to minimal systemic accumulation. The half life of the major metabolite of alcaftadine is two hours after ocular administration. Except for the metabolite, the rest of alcaftadine is excreted unchanged. Since alcaftadine is administrated at a small concentration and at a local site (the eye), it seems to have minimal systemic effects. Sales
Sales for Alcaftadine from the company Allergan began in July 2010. Since the beginning of sales, Alcaftadine prescriptions have increased until at least March 2012. From the time period of July 2010 until March 2012, cumulative sales have reached 139,000 prescriptions. Out of these 139,000 prescriptions there have been 104,000 unique patients. In March 2012, Alcaftadine exceeded sales of Elestat and this trend may continue as prescribers see the benefit of Alcaftadine and become more comfortable prescribing it. See also
Ketotifen

References
External links
"Alcaftadine". Drug Information Portal. U.S. National Library of Medicine.