The small particles of undissolved substance can cause damage to veins. Like alcohol , barbiturates depress the central nervous system and have similar effects lasting from 3 to 8 hours depending on the dose. A small dose usually makes people feel relaxed as if they'd had one or two drinks. With larger doses the effects are more unpredictable and the sedative effects takes over. There can be extreme and unpredictable emotional reactions and mental confusion.
Large doses can lead unconsciousness and eventually respiratory failure and death.
Fatal overdose is an ever present danger as the required amount for overdose is not much more than the recommended normal dose . The effects and dangers are greatly increased if Barbiturates are taken with alcohol Physical dependence is likely to develop with Barbiturates if a certain threshold value is exceeded. The dependence has a strong psychological as well as physical basis, and after high doses the withdrawal effects can include irritability, nervousness, inability to sleep, faintness and nausea, twitching, delerium and sometimes convulsions with may be associated with long term brain damage. Sudden withdrawl from high doses of Barbiturates can be fatal . Most of these risks are increased if Barbiturates are injected, which is by far the most dangerous form of drug taking.