How phenylbutazone works
Phenylbutazone inhibits the formation of prostaglandins. These tissue hormones are significantly involved in the development of pain, fever and inflammatory reactions.
The active ingredient blocks enzymes that are essential for the synthesis of prostaglandins (cyclooxygenases, or COX for short). In this way, phenylbutazone has analgesic (analgesic), antipyretic (antipyretic) and anti-inflammatory (antiphlogistic) effects.
Absorption, degradation and excretion
After oral ingestion, the drug is rapidly and completely absorbed from the gastrointestinal tract into the blood. In the liver, it is partially degraded to oxyphenbutazone, which is also anti-inflammatory.
The active ingredient and its degradation products are excreted primarily via the kidneys in the urine.
Phenylbutazone remains in the body for a very long time. Only about 50 to 100 hours after ingestion is half of it excreted again (half-life).
When is phenylbutazone used?
- acute attacks of gout
- acute attacks of rheumatoid arthritis
- acute attacks of Bekhterev’s disease (ankylosing spondylitis)
How phenylbutazone is used
Phenylbutazone used to be available in the form of tablets, coated tablets, suppositories and solutions (for injection). In the meantime, only a finished preparation for injection is available in Germany.
The dosage is determined by the physician. The usual dose is a single injection of 400 milligrams of phenylbutazone. In exceptional cases of prolonged use, regular blood count checks are recommended.
Phenylbutazone should be used for as short a time as possible.
What are the side effects of phenylbutazone?
Side effects are common. About 20 to 30 percent of patients develop adverse reactions to the drug. These include disorders of blood formation such as a deficiency of white blood cells (leukocytes) and a very severe reduction in the leukocyte subgroup of granulocytes.
Because the administration of the active ingredient also retains water and common salt in the body, tissue swelling (edema) and weight gain occur. Liver and kidney damage also develops in isolated cases.
Some patients also have an allergic reaction to the active substance, which can manifest itself, for example, with skin symptoms and asthma attacks.
What should be taken into account when using phenylbutazone?
Contraindications
Phenylbutazone must not be used in:
- known hypersensitivity to the active substance, other pyrazolones, or any of the other components of the drug.
- hypersensitivity to NSAIDs (such as acetylsalicylic acid, ibuprofen, and diclofenac)
- unexplained or active bleeding
- two or more gastrointestinal bleeding episodes in the past
- general bleeding tendency
- liver or kidney dysfunction
- severe heart failure (congestive heart failure)
Drug interactions
Phenylbutazone and other medications may interact if used at the same time.
Phenylbutazone also enhances the blood sugar-lowering effect of insulin and oral diabetes medications, as well as the anticoagulant effect of anticoagulants.
Furthermore, phenylbutazone impairs the excretion of methotrexate (agent used in cancer and after transplantation), so toxic amounts of it may accumulate in the body.
Age Limitation
Phenylbutazone should not be used in children and adolescents under 18 years of age.
Pregnancy and breastfeeding
Because phenylbutazone can have such a wide range of side effects and because better-tolerated alternatives are available, the active ingredient must not be used during pregnancy.
The active substance passes into breast milk and, according to the specialist information, must not be used during breastfeeding.
How to obtain medication with phenylbutazone
Phenylbutazone is subject to prescription in Germany. In Austria and Switzerland, there are no longer any human medicines registered with the active ingredient. Medicines for animals are not affected.
