A Medication Storage Temperature Witness for Homes Without Climate Control

SIMULATED, NOT MEASURED. An Arrhenius degradation model (activation energy 100 kJ/mol, range 80-120; time to 10% potency loss 90 days at 25 C) for a representative insulin-like drug class is applied to five home storage locations under winter, summer and heat-wave conditions. A working refrigerator is safe by a wide margin; every unrefrigerated location exceeds its exposure budget within one summer (windowsill red in 21.7 heat-wave days). A 48-hour fridge failure costs only 3.9% of budget. The required witness specification is derived from model sensitivity: +/-0.5 C accuracy, 10-minute sampling, 550-day coin-cell life, GBP 12.50 unit budget, showing cumulative green/amber/red. Only 11.4% of amber readings correspond to true potency loss above 10% under stated variation assumptions, so amber must not trigger discard.