What are the side effects of Phenacetin?

Phenacetin was once a commonly used analgesic and antipyretic, meaning it was used to relieve pain and reduce fever. However, it has since been banned or restricted in many countries due to its significant side effects and potential health risks. Understanding these side effects is crucial for appreciating why this drug is no longer in widespread use.

One of the most serious side effects of phenacetin is kidney damage. Long-term use of the drug has been linked to analgesic nephropathy, a form of chronic interstitial nephritis. This condition can lead to progressive kidney damage, potentially resulting in kidney failure. People who used phenacetin-containing products regularly for a prolonged period were found to be at a higher risk of developing this serious condition.

Another critical side effect is its carcinogenic potential. Studies have shown that phenacetin can lead to an increased risk of certain types of cancer, particularly urothelial cancers such as those affecting the bladder, renal pelvis, and ureter. The International Agency for Research on Cancer (IARC) has classified phenacetin as a Group 1 carcinogen, which means there is sufficient evidence to conclude that it can cause cancer in humans.

Phenacetin is also known to cause methemoglobinemia, a condition where an abnormal amount of methemoglobin is produced in the blood. Methemoglobin is a form of hemoglobin that is unable to effectively release oxygen to body tissues. This condition can result in symptoms such as cyanosis (a bluish coloration of the skin), headache, fatigue, shortness of breath, and at high levels, it can be life-threatening.

Liver toxicity is another serious side effect associated with phenacetin. The drug has been known to cause hepatic necrosis, hepatitis, and jaundice. Chronic use can lead to cumulative damage to liver cells, impairing the liver's ability to function properly and potentially leading to liver failure.

In addition to these severe health risks, phenacetin can cause a variety of other side effects. Gastrointestinal issues such as nausea, vomiting, and abdominal pain are common. It can also lead to allergic reactions, including rashes, itching, and more severe hypersensitivity reactions in some individuals.

Given these significant risks, phenacetin has been largely replaced by safer alternatives such as paracetamol (acetaminophen) and ibuprofen, which have similar analgesic and antipyretic effects but with a more favorable safety profile.

In summary, the side effects of phenacetin are severe and wide-ranging, impacting the kidneys, liver, blood, and increasing the risk of cancer. Its potential to cause serious health issues has led to its prohibition or restriction in many countries, underscoring the importance of using safer alternatives for pain and fever relief.