High doses of pseudoephedrine taken 2 hours prior to “diving” to 132 feet of seawater (5 ATA) while breathing pure O2 increases risk for CNS oxygen toxicity in unanesthetized rats

Abstract

Pseudoephedrine (PSE) salts (hydrochloride and sulfate) are commonly used as a decongestant by scuba divers. Anecdotal evidence collected by Divers Alert Network (DAN) suggests that use of PSE prior to making a high dose O2 dive (Nitrox or a rebreather using pure O2) increases the risk of CNS oxygen toxicity (CNS‐OT; i.e., seizures). We hypothesized that high doses of PSE reduces latency to seizure (LS) in unanesthetized rats breathing a lethal dose of HBO2 (5 ATA). Adult male rats were implanted with a radio‐transmitter for recording EEG, body temperature (TB), and activity. After ≥7 day recovery, a rat was given saline solution (control) or a dose of PSE hydrochloride intragastrically via gavage tube 2hr prior to “diving” (mg PSE/Kg): 0 (control), 80, 100, 120, 160 & 320 (9 rats/group). The rat was placed into a sealed chamber inside a hyperbaric chamber, which were pressurized in parallel with pure O2 and air, respectively, to 5 ATA until the onset of seizure. Our results show a significant dose dependent decrease in LS, compared to the control, at doses of 100–320 mg/Kg. We conclude that high doses of PSE should be avoided in deep dives breathing pure O2 as it increases the risk for CNS‐OT (DAN).