meat. pharmacokinetics in humans a study was conducted to define the pharmacological response of humans to ractopamine. a single oral dose of 40 mg of ractopamine hydrochloride was given to human volunteers. the drug was rapidly absorbed; the mean blood plasma half-life was around 4 hrs and it was not detected in plasma 24 hrs after dosing. less than 5% of total ractopamine excreted represented the parent drug, while the urinary metabolites were monoglucuronide and monosulfate conjugates, with ractopamine monosulfate being the major metabolite present. the metabolic fate of ractopamine hydrochloride is similar in the target species (pigs and cattle), laboratory animals, and humans. besides the pharmacology effect, ractopamine may cause intoxication effect; therefore, any consumption by humans of a meat and/or byproducts of animals that consumed ractopamine with feed for growth stimulation, may result in such clinical effects as tachycardia and other heart rate increases, tremor, headache, muscle spasm, or high arterial blood pressure. the effect of ractopamine on humans is not entirely known, but consumption of products that contain ractopamine residues is not advisable for persons with cardiovascular diseases. safety concerns target animal safety in swine, ractopamine is correlated with adverse effects, especially hyperactivity, trembling, and broken limbs, leading to censure by animal rights groups. in a conversation with boulder weekly newspaper, colorado state university professor of animal science temple grandin, an expert on animal welfare, described harmful effects of ractopamine on feedlot animals, such as cattle with stiff, sore, and lame limbs, and increased heat stress. in the same column, she also opines that meat from ractopamine-treated animals may be tougher. ractopamine use is a factor in the incidence of downer pigs, animals that are unable to move or stand. adverse effects acute toxicity oral ld50 levels in mice and rats are 3547–2545 mg/kg body weight (male and female) and 474–365 (male and female), respectively. genotoxicity and mutagenicity mutation studies in prokaryotes and eukaryotes show that ractopamine is not mutagenic. however, the results of several in vitro studies, including chromosome aberration tests in human lymphocytes, are positive. the positive genotoxic results are explained with limited evidence to be due to a secondary auto-oxidative mechanism from ractopamine-catechol-producing reactive intermediates. carcinogenicity ractopamine is not considered to be a carcinogen and not listed by iarc, ntp, acgih, or osha. cardiovascular effects dose-dependent changes of heart rate and cardiac output are observed within the first hour after administration of ractopamine and gradually return to baseline values. the systolic blood pressure will also increase in a dose-dependent manner, while the diastolic pressure remains unchanged. musculoskeletal effects skeletal muscle tremor is the most common adverse effect of beta-agonists, and is more likely to be seen after oral administration than after inhalation. tremor results from an imbalance between fast- and slow-twitch muscle groups of the extremities, and its severity varies greatly between individuals. behavioral changes in humans restlessness, apprehension, and anxiety were reported effects after the use of various beta-agonists, particularly after oral or parenteral treatment. in pilot clinical trials with ractopamine, four patients showed little evidence for central nervous system stimulation. whether long-term treatment with these drugs results in the development of tolerance to these adverse effects is unclear. analytical method for residues in livestock in cattle and swine tissue, it was found in 2007 that a procedure for the analysis of ractopamine residues in liver or muscle can be performed by high performance liquid chromatography (hplc) with fluorescence detection. the confirmatory method include reversed-phase hplc/electrospray ionization triple tandem quadrupole mass spectrometry. the limit of quantification of the drug using this lc/ms instrument was shown to be 1 ng/g (1 ppb). in cattle, a 2018 chinese study promoted the use of hair as an indelible test of feed containing ractopamine. in popular culture stuntman and comedian steve-o has publicly spoken of his involvement as a test subject in an early ractopamine study whose aim was to determine the stress limits of ractopamine saturation in humans. glover says "based on how dangerous the study was, the more money you get."