Final answer:
The effects of a barbiturate and alcohol taken together are synergistic and can be dangerous, multiplying their depressant effects on the central nervous system, leading to a significant risk of overdose and severe health consequences.
Step-by-step explanation:
The effects of a barbiturate and alcohol taken together are synergistic and can be dangerous. This is because both substances are central nervous system depressants and when used together, their effects on the body are not merely additive but multiplicative, leading to an increased risk of overdose and potentially life-threatening respiratory depression. For instance, if a benzodiazepine increases the frequency of GABA channel opening by 300% and a barbiturate increases the duration of their opening by 300%, their combined effects would increase the channels' overall function by 900%, much greater than the sum of their individual effects. This may result in an overdose, characterized by symptoms like sluggishness, difficulty in thinking, slow speech, and in severe cases, coma or death.
Such interactions underscore the importance of medical supervision especially for individuals who are drug dependent, as withdrawal from these substances can be dangerous without proper medical care. Ultimately, the use of barbiturates in medical practice has decreased due to the risks associated with their use, and they have been largely replaced by substances with a lower risk of addiction and overdose.