A hit of shisha [a type of crystal methamphetamine brewed from barbiturates and other ingredients including alcohol, chlorine and even battery acid], concocted in makeshift laboratories around Athens, costs 3 to 4 euros. Doses come in the form of a 0.01-gram ball, leaving many users reaching for hits throughout the day. They include prostitutes in Omonia, who have been selling their services for as little as 10 to 15 euros, a price that has shrunk along with the income of clients afflicted by the crisis. Shisha is most often smoked. But it is increasingly being taken intravenously; because of the caustic chemicals it contains, a rising number of users are winding up in the emergency room. Health experts say the injections are also adding to an alarming rise in H.I.V. cases around Greece, which surged more than 50 percent last year from 2011 as more people turn to narcotics.