Priapism is a very rare adverse event that can be potentially serious.US Food and Drug Administration-commissioned studies in 2011, indicate that in children, young adults, and adults there is no association between serious adverse cardiovascular events (sudden death, heart attack, and stroke) and the medical use of methylphenidate or other ADHD stimulants.Because some adverse effects may only emerge during chronic use of methylphenidate, a constant watch for adverse effects is recommended.A 2018 Cochrane review found that methylphenidate might be associated with serious side effects such as heart problems, psychosis, and death. The certainty of the evidence was stated as very low.A 2018 review found tentative evidence that it may cause both serious and non-serious adverse effects in children. Overdose
The symptoms of a moderate acute overdose on methylphenidate primarily arise from central nervous system overstimulation; these symptoms include: vomiting, nausea, agitation, tremors, hyperreflexia, muscle twitching, euphoria, confusion, hallucinations, delirium, hyperthermia, sweating, flushing, headache, tachycardia, heart palpitations, cardiac arrhythmias, hypertension, mydriasis, and dryness of mucous membranes. A severe overdose may involve symptoms such as hyperpyrexia, sympathomimetic toxidrome, convulsions, paranoia, stereotypy (a repetitive movement disorder), rhabdomyolysis, coma, and circulatory collapse. A methylphenidate overdose is rarely fatal with appropriate care. Following injection of methylphenidate tablets into an artery, severe toxic reactions involving abscess formation and necrosis have been reported.Treatment of a methylphenidate overdose typically involves the administration of benzodiazepines, with antipsychotics, α-adrenoceptor agonists and propofol serving as second-line therapies. Addiction and dependence
Methylphenidate is a stimulant with an addiction liability and dependence liability similar to amphetamine.
Bacteria can enter the joint by:

The bloodstream from an infection elsewhere (most common)
Direct penetration into the joint (arthrocentesis, arthroscopy, trauma)
A surrounding infection in the bone or tissue (uncommon, from osteomyelitis, septic bursitis, abscess).Microorganisms in the blood may come from infections elsewhere in the body such as wound infections, urinary tract infections, meningitis or endocarditis. Sometimes, the infection comes from an unknown location. Joints with preexisting arthritis, such as rheumatoid arthritis, are especially prone to bacterial arthritis spread through the blood. In addition, some treatments for rheumatoid arthritis can also increase a persons risk by causing an immunocompromised state. Intravenous drug use can cause endocarditis that spreads bacteria in the bloodstream and subsequently causes septic arthritis. Bacteria can enter the joint directly from prior surgery, intraarticular injection, trauma or joint prosthesis. Risk factors
In children, although septic arthritis occurs in healthy children and adolescents with no co-occurring health issues, there are certain risk factors that may increase the likelihood of acquiring septic arthritis. For example, children with renal osteodystrophy or renal bone disease, certain hematological disorders and diseases causing immune suppression are risk factors for childhood septic arthritis.The rate of septic arthritis varies from 4 to 29 cases per 100,000 person-years, depending on the underlying medical condition and the joint characteristics. For those with a septic joint, 85% of the cases have an underlying medical condition while 59% of them had a previous joint disorder. Having more than one risk factor greatly increases risk of septic arthritis. Age over 80 years
Diabetes mellitus
Osteoarthritis
Rheumatoid arthritis.