Beta Blockers & Diving: Interactions between beta-adrenergic antagonists and SCUBA reside both in the drug's intended and unintended effects. As regards intended effects, beta-blockers interfere with the actions of adrenaline on beta receptors. Among other things, they slow nerve impulses traveling through the heart. As a result, the heart does not work as hard and arterial BP is decreased. Now, this desired limitation in cardiac output may undesirably reduce exercise tolerance such that possible unexpected rigors of diving (e.g., very intense currents, a buddy rescue, a long surface swim in rough conditions) cannot be negotiated. It is for this reason diving medicine recommends that those taking beta-blockers be able to attain, or closely reach, 13 mets upon exercise stress testing without angina, shortness of breath, EKG abnormality or other worrisome event. As regards unintended effects, otherwise termed adverse reactions or side effects, of concern to the diver is that this class of drug can cause cold hands and feet, vomiting, tiredness, dizziness/lightheadedness and anxiety. It obviously would not be good if sedative effects interacted with increased partial pressures of nitrogen to exaggerate narcosis, or if anxiety predisposed to diver panic. It is for this reason that, as with all drugs, a beta-blocker should be given an adequate topside trial to assess for problematic side effects before attempting SCUBA. Finally, as regards the effects of the increased ambient pressures inherent in SCUBA on blood pressure, there seem to be none of significant concern. While some cardiac changes do occur with SCUBA, such as increased heart rate and decreased stroke volume, neither systolic nor diastolic BP appear to be meaningfully affected.  In conclusion, otherwise healthy and fit divers taking only a modest dose of a beta-blocker seem at very little additional risk due to the medication. Should there be issues, there is a wide variety of alternative classes of drugs to manage HBP. Helpful? This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual and should not be construed as such. © Doc Vikingo Back to Doc Vikingo's Divers Resource Page Contact Doc Vikingo Back to Awoosh Main Directory