, Dogs are better able to tolerate aspirin than cats are. Aspirin should not be given to children or adolescents to control cold or influenza symptoms, as this has been linked with Reye's syndrome.  For those weighing less than 70 kilograms (154 lb), low dose is effective for preventing cardiovascular disease; for patients above this weight, higher doses are required. In 1915, the first Aspirin tablets were made.  Some studies recommend aspirin on a case-by-case basis, while others have suggested the risks of other events, such as gastrointestinal bleeding, were enough to outweigh any potential benefit, and recommended against using aspirin for primary prevention entirely.  More recent data also suggest salicylic acid and its derivatives modulate signaling through NF-κB. , Aspirin is an effective analgesic for acute pain, although it is generally considered inferior to ibuprofen because aspirin is more likely to cause gastrointestinal bleeding. With respect to the hydrogen bonds formed by the carboxylic acid groups, both polymorphs form identical dimer structures. [original research? Aspirin-modified PTGS2 (Prostaglandin-endoperoxide synthase 2) produces lipoxins, most of which are anti-inflammatory. Adding cold water stops the reaction, and the products are filtered, yielding aspirin. Festival of Sacrifice: The Past and Present of the Islamic Holiday of Eid al-Adha.  When small doses (less than 250 mg in an adult) are ingested, all pathways proceed by first-order kinetics, with an elimination half-life of about 2.0 h to 4.5 h. When higher doses of salicylate are ingested (more than 4 g), the half-life becomes much longer (15 h to 30 h), because the biotransformation pathways concerned with the formation of salicyluric acid and salicyl phenolic glucuronide become saturated.  People with hemophilia or other bleeding tendencies should not take aspirin or other salicylates. Secondary headaches, meaning those caused by another disorder or trauma, should be promptly treated by a medical provider. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit in the United States of 5 mg/m3 (time-weighted average).  It is generally not recommended for routine use by people with no other health problems, including those over the age of 70. , As much as 80% of therapeutic doses of salicylic acid is metabolized in the liver. Aspirin is a weak acid that is only slightly soluble in water. , For people who have already had a heart attack or stroke, taking aspirin daily for two years prevented 1 in 50 from having a cardiovascular problem (heart attack, stroke, or death), but also caused non-fatal bleeding problems to occur in 1 of 400 people. The elusive second polymorph was first discovered by Vishweshwar and coworkers in 2005, and fine structural details were given by Bond et al. , On 9 July 2015, the FDA toughened warnings of increased heart attack and stroke risk associated with nonsteroidal anti-inflammatory drugs (NSAID).