How long would u have to abuse street-amphetamines (not meth the normal amps) and how often until you damage your neurons ?
Amphetamine can produce neurotoxic effects. There are clear evidences about this both in animals and humans. But it is very difficult to know the toxic dosage and pattern of use. Amphetamine has been used as therapeutic drug up to 40 mg/daily dosage (oral route) without evidence of neurotoxicity in long time. Intranasal or intravenous route probably enhance the possibility of neurotoxicity. The purity (or presence of toxic adulterants) of street amphetamine is unknown but it is also an important factor. It is possible, also, that a occasional high dosage of amphetamine can produce a direct neurotoxic effect or other cerebrovascular problems.
In conclusion, it is unlikely that occasional, sporadic, recreational use of common dosages of amphetamine will produce neurotoxic effects but high dosages or intensive (daily or very common) patterns of use will be probably exposed to this risk.