What is a common side effect of both benzodiazepines and barbiturates?

Benzodiazepines and barbiturates are both central nervous system (CNS) depressants, and a notable side effect they share is respiratory depression. This is particularly dangerous because it can lead to inadequate ventilation and hypoxia, especially in higher doses or when combined with other depressants, such as alcohol or opioids.

Respiratory depression occurs because these substances enhance the effects of gamma-aminobutyric acid (GABA), a neurotransmitter that inhibits neuronal activity, leading to decreased respiratory drive. This can be especially acute during overdose situations, which can precipitate significant medical emergencies.

Other options like euphoria, increased heart rate, and muscle rigidity may not be common side effects. Euphoria is more associated with various substances, particularly opioids or stimulants, rather than being a universal side effect of these depressants. Increased heart rate is typically a compensatory response rather than a direct effect of these drugs. Muscle rigidity is not characteristic of benzodiazepines or barbiturates; it is more often seen with other drug classes, such as antipsychotics.