Why is respiratory arrest the most common cause of death from opiate overdose?

See below.

Explanation:

The ventilatory control system is highly vulnerable to exogenous administered opioid analgesics. Particularly respiratory depression is a potentially lethal complication that may occur when opioids are overdosed or consumed in combination with other depressants such as sleep medication or alcohol.

Opioids activate specific transmembrane neurotransmitter receptors (mu, kappa, delta) that couple G proteins. G proteins are molecular intermediaries that initiate the intracellular communication process.

Opioid receptors are located in the central and peripheral nervous system. The effects of activation of neuronal mu receptors will depend on the location of the receptor, the types of G proteins present in the activated neural tissues, and the frequency and duration of activation. Activation of mu receptors in the central nervous system results in responses such as respiratory depression, analgesia, euphoria, and miosis. Stimulation of peripheral mu opioid receptors, in smooth muscle of the bronchi and intestines, results in cough suppression and opioid-induced constipation.