Excessive use of stimulants can promote stimulant psychosis. Examples include stimulants, amphetamines, and antihistamines. Unlike most stimulants, caffeine has no addictive potential. Secretions from dendrobatids are also showing promise as muscle relaxants, heart stimulants and appetite suppressants. Medications that cause vasoconstriction include&colon; antihistamines, decongestants, and stimulants. Methylphenidate and other ADHD stimulants also improve task saliency and increase arousal. Examples are stimulants (including caffeine) and exercise. MDMA is less addictive than other stimulants such as methamphetamine and cocaine. Jones was said to be abusing injectable Valium, Quaaludes, stimulants, and barbiturates. Relatively high doses of stimulants cause cognitive deficits. Withdrawal from stimulants such as cocaine does not have major medical complications. Relatively high doses of dopaminergic stimulants will result in cognitive deficits. The combination of antipsychotics like aripiprazole with stimulants should not be considered an absolute contraindication. Both stimulants and substitutes relieve symptoms to some extent. MDMA is used less often than other stimulants, typically less than once per week.