Allopurinol is a medication that is available in oral form as a tablet or as an injection given in the doctor’s office. A generic form of allopurinol is available, although it is also available as a brand name drug, where it is known as Zyloprim or Lopurin. Allopurinol is given for conditions resulting from elevated uric acid levels, such as gout.
Allopurinol side effects have been well-studied throughout the years. This should not be surprising given how common gout, and other conditions associated with elevated uric acid levels, are.
It is important to consider side effects when considering any medication, and allopurinol side effects are no different. In fact, allopurinol is associated with a number of serious side effects, many of which are tied to serious reactions that this medication causes to the skin. Allopurinol also has a number of significant drug interactions and contraindications that are important to be aware of before starting this medication.
In spite of the well-known allopurinol side effects, this medication is a mainstay in the prevention of gout. It can also be given to treat a gout attack, although it was not historically used for this purpose.
What Is Allopurinol?
Allopurinol is a xanthine oxidase inhibitor that is used to prevent gout attacks by reducing elevated uric acid levels in the blood. Xanthine oxidase is an enzyme that yields reactive oxygen species. In humans and other animals, this enzyme is associated with the catabolism, or break down, of compounds called purines. Purines are commonly found in meat and fish products, as well as some vegetables like spinach and asparagus. Purines are broken down to uric acid, which is a normal component of urine.
The key to understanding allopurinol and allopurinol side effects is to be familiar with uric acid and the role that it plays normally in the human body. Uric acid is normally produced by xanthine oxidases from their breakdown of purines. It is a typical component of urine and, as mentioned briefly, it can become elevated in the body, because some compounds that we eat as food result in the body having a higher than normal concentration of uric acid. This elevated concentration of uric acid results in gout, as well as other conditions of uric acid elevation like kidney stones.
Uric acid is somewhat interesting, because the symptoms of elevated concentration of this compound, symptoms which allopurinol is designed to treat, are essentially due to the compound being deposited in various parts of the body, like the joints of the hand, the kidneys, or even in the skin. The purpose of allopurinol is to block the enzyme that leads to the production of uric acid. Blocking of xanthine oxidase by allopurinol results directly in a lower concentration of uric acid in the body, as less is being produced. This also prevents symptoms of uric acid excess, which is the underlying purpose of the medication.
Allopurinol works as a purine analog, meaning that it resembles the purine compounds that xanthine oxidase is designed to breakdown, in this case hypoxanthine. Allopurinol is an isomer of hypoxanthine. By blocking xanthine oxidase, this medication not only reduces the concentration of uric acid produced, but it also leads to the increase of the purine compounds xanthine and hypoxanthine.
Although the primary mechanism of action of allopurinol is to block xanthine oxidase, this medication also indirectly reduces purine synthesis due to an increase of hypoxanthine in the blood, as a result of xanthine oxidase inhibition.
Although allopurinol side effects will be discussed in following sections, it is important to note the contraindications and interactions associated with the administration of allopurinol as a medication for the treatment of gout and other conditions associated with elevated uric acid, like kidney stones and skin tophi. Allopurinol interacts with azathioprine, an important immunosuppressant medication, and 6-mercaptopurine, which is used as a treatment for cancer, ulcerative colitis, and other conditions. The main drug interactions are as follows:
Allopurinol increases the concentrations of these medications, so it would be necessary for your doctor to adjust the dose of your medication if you are taking any of these. Allopurinol drug interactions also include reducing the effectiveness of certain drugs or making particular side effects more common. Although side effects of allopurinol specifically will be covered later, this medication can make skin rashes more common if administered with amoxicillin, ampicillin, certain diuretics, and certain high blood pressure medications. Allopurinol increases the activity of the following medications:
Although allopurinol has become known for its use in the treatment of gout, this medication was not developed for that purpose. Allopurinol was synthesized for the first time in the 1950s, and was researched to see if it could be used as a treatment for acute lymphoblastic leukemia, or ALL. This medication was not found to be especially effective for use in leukemia, and research became focused on using for the treatment of gout in the 1960s.
Allopurinol was initially approved by the Food and Drug Administration, or FDA, in 1966, and was sold under the trade name of Zyloprim. Allopurinol is now available all over the world, as it is now a generic. This medication is known by a wide variety of names, although it is still commonly referred to as Zyloprim or allopurinol. Pure allopurinol is a white powder, although as a drug formulation it is available as a tablet or as intravenous (fluid) medication.
It goes without saying that the good points of allopurinol are that it is a highly effective treatment for gout and other similar conditions, and it is available as a generic, so it’s less expensive than many medications that are still under the initial trademark patents that the drug manufacturers were granted when these medications were approved. Although some reactions of allopurinol may be fatal, the medication is generally considered to be safe and well-tolerated.
As mentioned previously, allopurinol reduces the concentration of uric acid in the body by inhibiting xanthine oxidase, an enzyme. For this reason, allopurinol can be given to treat conditions that are associated with, or caused by, elevated concentrations of uric acid, or urate. Although most people are familiar with gout, this is only one of the conditions associated with elevated uric acid. The following conditions associated with uric acid excess can be treated by administering allopurinol:
Although epilepsy is not associated with elevated uric acid levels, like gout or the other conditions on the list, allopurinol is effective here because it works as an adenosine against and does not interfere with the concentration of other epilepsy medications in the blood. Allopurinol side effects will be discussed in the next section, but one of its advantages is that it can be given to people with poor kidney function due to renal insufficiency, kidney failure, or the like.
Allopurinol Side Effects
The biggest downside of most medications is often the side effects. Allopurinol side effects can be serious and men and women taking this medication should be aware of them. Individuals taking this medication should stop taking it and seek emergency medical helps if they experience symptoms associated with an allergic reaction such as difficulty breathing, hives, swelling of face, tongue, throat, or lips. Serious side effects of this medication may include:
Allopurinol specifically has a reputation for skin reactions, some of which are very serious. Many of the symptoms listed above are associated with a hypersensitivity syndrome caused by allopurinol. This consists of rash, fever, abdominal pain, and worsening kidney functioning. This hypersensitivity syndrome is considered the most serious side effect of allopurinol, and it is potentially fatal. Not all rashes that come as allopurinol side effects are as serious as this. Skin rashes are a more common side effect with this medication, and usually result in simple discontinuation of the medication.
The decision of whether or not to take a medication is not always an easy one. Like any medication, allopurinol can result in changes, although allopurinol’s side effects have to be weighted based on their seriousness and the efficiency of the drugs. Some allopurinol side effects are serious enough to warrant stopping the medication completely, while others may be managed by a doctor. A major advantage of allopurinol is not only that it can drastically reduce uric acid in the body, but it can be used both to prevent conditions associated with elevated uric acid and to treat them.