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Preparation H is a brand of medications made by Pfizer, used in the treatment of hemorrhoids. Hemorrhoids are caused at least in part by inflamed blood vessels, and most versions of Preparation H work by reducing inflammation in blood vessels.
Originally, as far back as the 1930s, it was packaged in a tube like toothpaste, with a similar consistency. Now named Wyeth and owned by Pfizer, the company incorporated in 1926 as American Home Products, or AHP, and "one of AHP's earliest prizes was the acquisition of a sunburn oil in 1935 that the company transformed into Preparation H, which became one of the world's best-selling hemorrhoid treatments." AHP changed its name to Wyeth in 2002, and was then bought by Pfizer in 2009, who was reported to have paid 68 billion dollars.
There are several formulations in production. For example, some are in a water-based gel, while some are petroleum jelly-based. It can come as a suppository, or as a medicated wipe. The active ingredients range from simple moisturizers with witch-hazel astringent to preparations containing drugs such as phenylephrine, pramoxine, and hydrocortisone. Some also contain inactive ingredients such as aloe vera. Formulations available vary from one country to another.
Today, some Preparation H products have phenylephrine, a drug that constricts blood vessels, as active ingredient, in a 0.25% concentration. This drug is more commonly used as a decongestant in cold medications, since restricting blood flow in the sinuses will reduce the amount of mucus and/or liquid flow they create, in runny noses. Because hemorrhoids are caused by inflamed blood vessels, restricting the blood flow may well reduce the size of the swelling, and reduce the pain or discomfort the person feels. Another version of Preparation H has hydrocortisone as its only active ingredient, in a 1% concentration. Again, hydrocortisone reliably reduces inflammation and swelling. A witch hazel medicated wipe is also available under the Preparation H brand.
The Canadian formulation of Preparation H includes a yeast extract called BioDyne, which has been removed from the formulation previously sold in the United States in 1995. This yeast extract is believed by Pfizer to remove wrinkles from skin and heal dry, cracked, and irritated skin. The Canadian formulation has acquired a market in the United States as a skin cream with an anti-wrinkle active ingredient.
In the 1960s, Preparation H used the droll slogan "Effective even in cases of long standing". The current tag line, "I Should Have Used Preparation H," is a registered trademark, .
Supply disruption 
As of May 5, 2011, the Pfizer website noted, "There is currently a supply disruption on Preparation H suppositories. We are working diligently to get product back on store shelves." No reason for the supply disruption was given.