Also available in linctus form, like a cough medicine. It is prescribed to habitual amphetamine injecters in the UK, (or it used to be) because there's no way to inject a sugar suspension so it can only be taken orally.
I know this from the personal experience of knowing a guy who injected; he'd sell me the dex linctus in order to buy amphetamine sulphate in powder form so that he could bang it into a vein.
(I think I got the better end of the deal)