), an immunosuppressive drug frequently used to prevent transplant rejection; the two drugs should therefore not be administered concomitantly. Orlistat can also impair absorption of the antiarrhythmic amiodarone. The Medicines and Healthcare products Regulatory Agency (MHRA) has suggested the possibility that orlistat could reduce the absorption of antiretroviral HIV medications. Mechanism of action
Orlistat works by inhibiting gastric and pancreatic lipases, the enzymes that break down triglycerides in the intestine. When lipase activity is blocked, triglycerides from the diet are not hydrolyzed into absorbable free fatty acids, and instead are excreted unchanged. Only trace amounts of orlistat are absorbed systemically; the primary effect is local lipase inhibition within the GI tract after an oral dose. The primary route of elimination is through the feces. Orlistat was also found to inhibit the thioesterase domain of fatty acid synthase (FAS), an enzyme involved in the proliferation of cancer cells but not normal cells. However, potential side effects of orlistat, such as inhibition of other cellular off-targets or poor bioavailability, might hamper its application as an effective antitumor agent. One profiling study undertook a chemical proteomics approach to look for new cellular targets of orlistat, including its off-targets. Orlistat also shows potential activity against the Trypanosoma brucei parasite.Orlistat prevents approximately 30% of dietary fat from being absorbed. Legal status
Orlistat is available both with and without a prescription. Australia and New Zealand
In Australia and New Zealand, orlistat is available as a "Pharmacist Only Medicine.
Hereditary pancreatitis (HP) is an inflammation of the pancreas due to genetic causes. It was first described in 1952 by Comfort and Steinberg but it was not until 1996 that Whitcomb et al isolated the first responsible mutation in the trypsinogen gene (PRSS1) on the long arm of chromosome seven (7q35). The term "hereditary pancreatitis" is used when a genetic biomarker is identified, and "familial pancreatitis" otherwise. Presentation
HP is characterised by attacks of epigastric pain, which are often associated with nausea and vomiting. Symptoms may start shortly after birth but onset varies periodically, with some patients not exhibiting symptoms until adulthood. There is usually progression to chronic pancreatitis with endocrine and exocrine failure and a mortally increased risk of pancreatic cancer. Lifetime risk of cancer has been variously calculated as 35–54% to the age of 75 years and screening for early pancreatic cancer is being offered to HP sufferers on a scientific basis. Some patients may choose to have their pancreas surgically removed to prevent pancreatic cancer from developing in the future.The epidemiology of HP follows a similar pattern to alcohol-associated chronic pancreatitis, but there are important differences. For example, HP typically has an earlier age of pancreatitis onset; although malabsorption and diabetes mellitus occur at a later stage in the disease progression. Genetics
The vast majority of the cases of HP are caused by substitutions, at base 365 (c.365G>A) and base 86 of the cDNA (c.86A>T) on the PRSS1 gene.