Structural Biochemistry/Acetaminophen

Acetaminophen aka Paracetamol pronounced ‘a set a mee’ no fen’ is an over-the counter (OTC) drug that is composed of a reaction between p-aminophenol and acetic anhydride. The generic name for acetaminophen is Tylenol or MAPAP. Acetaminophen is a derivative of acetanilide. It is used to temporarily relieve mild headaches, muscle pain, sore throats, and fevers. Acetaminophen can also be used to as an anti-inflammatory drug for osteoarthritis which is caused by the “wear and tear” of the joints due to incorrect joint alignment. This drug produces its effect by altering the way in which the body senses pain and creating a feedback mechanism to cool the body. This drug does not block and inhibit the enzyme, cyclooxygenase (COX), which serves as a catalyst for the production of prostaglandins which in turn is responsible for producing pain, inflammation, and a fever within the peripheral nervous system like other non-opioid analgesics. It is rather believed that acetaminophen blocks COX-3 in the central nervous system instead.

Although acetaminophen is typically found as a tablet, it can also be in the form of a solution, suspension, chewable tablet, suppository, drops, etc. Although it is an over-the-counter drug that is readily available, it is important to know the risks and symptoms of taking it like any other drug. Acetaminophen should not be taken in combination with alcohol. Overuse of acetaminophen can cause lead to liver damage, and in serious but rare cases, liver transplants may be required. In addition, reported side effects of acetaminophen may include itching, swelling, hoarseness, and breathing difficulty—all of which should be taken into consideration. If symptoms persists, stop taking the medication and consult a doctor.

The use of this medicine for children can be extremely potent and life-threatening. When treating a child with acetaminophen, directions and dosage should be followed with extreme care. Drops are usually given to infants, but since they contain a higher concentration of acetaminophen, be sure to check and give the dosage according to their weight and age.

In addition, some acetaminophen tablets contain additional sweeteners so people diagnosed with Phenylketonuria (PKU) should be aware and careful because their bodies are unable to breakdown phenylalanine (Phe), which can be harmful to the human brain at high levels to those who are diagnosed with PKU.

When taking cold medicine, you should avoid taking multi-symptom cold medications such as Dayquil and Theraflu because these drugs usually contain a dosage of acetaminophen. Instead, one should take medicine base on specific symptoms. For example, to treat a nasal congestion, it is recommended that you use Sudafed (common name pseudoephedrine); Robotussin for coughs; Tylenol for fever and achiness; and Ricolla for throat pains, etc.

Synthesis
In the lab, paracetamol(Acetaminophen) is easily prepared by nitration| nitrating phenol with sodium nitrate, separating the desired 4-Nitrophenol| p-nitrophenol from the ortho- byproduct, and reducing the nitro group with sodium borohydride. The resultant p-aminophenol| p-aminophenol  is then acetylated with  acetic anhydride. The industrial process is analogous, but hydrogenation is used instead of the sodium borohydride reduction.

Another simpler synthesis is by Hoechst-Celanese. This involves direct acylation of phenol with acetic anhydride catalyzed by HF. Thus converting the ketone to a ketoxime  with  hydroxylamine, then followed by the acid-catalyzed  Beckmann rearrangement  to give the amide.

Side Effects
It is not likely for acetaminophen to produce side effects. People who claim or present symptoms of side effects created by acetaminophen are generally due to overdose of acetaminophen.

Common side effects from overdose include:
 * nausea
 * jaundice (yellow skin or eyes)
 * appetite loss
 * sweating
 * irritability
 * abdominal pain
 * liver failure
 * kidney failure
 * heart problems
 * coma
 * seizures
 * Death (in extreme conditions)