Which drug is known to have antidiuretic effects that may contribute to water intoxication?

Pethidine is an opioid analgesic that can have antidiuretic effects, which may lead to water retention and, in some cases, water intoxication. This is due to its influence on the central nervous system, which can interfere with the regulation of water balance. Specifically, pethidine can stimulate the release of antidiuretic hormone (ADH), leading to increased reabsorption of water in the kidneys. Excessive water intake, combined with impaired excretion, can result in a dilutional state that affects electrolyte balance and may progress to water intoxication, characterized by symptoms like headache, nausea, and in severe cases, seizures or coma.

Other options represent different types of medications that lack these specific antidiuretic properties. For instance, magnesium sulfate is primarily used to manage seizures and can have a laxative effect, while fentanyl and ketamine are mainly used for pain management and anesthesia, respectively, without significant antidiuretic effects. Thus, pethidine stands out in this context due to its potential contribution to water intoxication through its pharmacological action.