Propranolol

Common (>10% users at chronic dose; less at single PRN dose)

• Bradycardia / low pulse — expected pharmacodynamic effect. At PRN 20 mg in a healthy 20-year-old, HR drop is ~5-15 bpm. If resting HR is already <50 bpm, dose down or skip.
• Cold extremities — reduced peripheral perfusion. Hands/feet feel cold or tingly. Usually mild and self-limiting.
• Mild fatigue / lethargy at higher chronic doses (uncommon at PRN doses).

Less common (1-10%)

• Dizziness / lightheadedness — usually positional; resolves with hydration and avoiding rapid postural change.
• Nausea / GI upset — take with food.
• Bronchospasm — relevant to anyone with asthma history. Propranolol's β2 blockade can trigger bronchoconstriction. Asthmatics should use β1-selective alternatives (metoprolol, atenolol) instead, or avoid beta-blockers entirely.
• Vivid dreams / nightmares — small minority of chronic users report this. Mechanism unclear (possibly REM-architecture effects from CNS penetration). Rare at PRN dosing.
• Erectile dysfunction at chronic dose — uncommon; not relevant to PRN single-event use.

Rare-serious (<1% but worth knowing)

• Severe bradycardia or AV block — particularly relevant if the user has pre-existing conduction disease. ECG screening before chronic use, not before a single PRN trial dose.
• Bronchospasm in undiagnosed asthma — first-dose risk. The reason for a low-stakes test dose first.
• Hypoglycemia masking — propranolol blunts the adrenergic warning signs of low blood sugar (tachycardia, tremor) so a hypoglycemic episode can become severe before being recognized. Relevant for diabetics on insulin/sulfonylureas. Not relevant for Dylan.
• Withdrawal rebound — abrupt cessation after chronic high-dose use can produce rebound tachycardia, hypertension, and (theoretically) MI in cardiac patients. Not relevant to PRN use; relevant if Dylan ever migrates to chronic dosing.
• Depression / psychiatric effects — older literature suggested chronic high-dose propranolol increases depression risk. More recent meta-analyses (Riemer et al. 2021) show minimal-to-no effect on mood in non-cardiac populations. Probably an over-stated risk; still worth knowing.

Specific watch periods

• First test dose: confirm no bronchospasm, no excessive bradycardia. Have a plan to abort if the response is unexpected (rest, hydrate, wait it out — propranolol is competitively reversible and short-half-life).
• First sparring/cardio day after exposure — verify the workout feel. If you tested propranolol on a Friday evening and your Saturday morning sparring feels notably worse, that's a sign the half-life carried over more than expected; space the next dose further from cardio events.

Athletic-specific risks (load-bearing for Dylan)

• Max HR cap. β1 blockade prevents the heart from achieving full sympathetic-driven max HR. For aerobic athletes, this cuts ~15-30 bpm off max HR and proportionally reduces cardiac output and VO2max during the dose window. For MMA conditioning (rounds, sparring, intervals), this is a real performance hit — you'll feel like the gas tank is half-size.
• Lactate clearance. Less well-characterized but β2 blockade impairs muscle glycogenolysis and possibly fat mobilization, which can shorten time-to-fatigue at moderate-to-high intensity.
• Thermoregulation. Reduced peripheral blood flow under propranolol = slightly impaired heat dissipation in hot training environments.
• Practical rule for Dylan: do not dose propranolol on any day with cardio sparring, hard pad work, or interval conditioning. PRN propranolol is compatible with technical drilling / light flow / rolling, not with full-output conditioning.