Kafeini, Kafeni uye Kafini itetsa ye Udzira Mutandi Wopakati (UMP; CNS kuChingezi) inokurudzira yekirasi ye metirisandine (methylxanthine). Kune akati wandei anozivikanwa nzira dzekuita kutsanangura mhedzisiro ye kafeni. Chinonyanya kukosha ndechekuti inovharira nekudzoka kuita kweadenosine pama receptors ayo uye nokudaro inodzivirira kutanga kwekukotsira kunokonzerwa neadenosine. Kafeni zvakare inokurudzira zvimwe zvikamu zve Udzira Mtandi weUpangamene (ANS). Kafeni inovava, gokomara jena repurini (white crystalline purine), methylxanthine alkaloid, uye ichemushonga chine hukama ne (adenine) uye (guanine) mabhesi e (deoxyribonucleic acid) uye (ribonucleic acid). Inowanikwa mumhodzi, muchero, nzungu, kana kuti mashizha emiti yakati wandei inozvarwa muAfurika, Mabvazuva eEzhiya ne Amerika Chamhembe, uye inobatsira kuidzivirira pamhuka dzinodya uswa uye pamakwikwi nekudzivirira kumera kwembeu dziri pedyo, pamwe nekukurudzira kudyiwa nemhuka dzakasarudzwa dzakaita senyuchi dzeuchi. Iyo inonyanya kuzivikanwa kunobva kafeni ibhinzi yekofi, mhodzi yechirimwa cheKofi. Vanhu vanogona kunwa zvinwiwa zvine kafeni kuderedza kana kudzivirira kukotsira uye kuvandudza kugona kwekuziva. Kugadzira zvinwiwa izvi, kafeni inotorwa nekunyudza chigadzirwa chechirimwa mumvura, maitiro anonzi (infusion). Zvinwiwa zvine kafeni, zvakaita sekofi, svutugadzike, uye (cola), zvinonwiwa pasirose muhuwandu hwakawanda.