Summary Background: Hook phlebectomy is usually performed under local anaesthesia. Several modifications of local anaesthesia have been proposed, including the reduction of the concentration of the local anaesthetic, the increase of the volume, the addition of norepinephrine and sodium bicarbonate. Patients, method: Three episodes are reported of painless skin necrosis after local anaesthesia using mepivacain (0.5 or 1%) with added sodium bicarbonate (8.4%, 1 : 10). Results: Degradation of the solution used for local anaesthesia was the cause of the necroses. The stopcock securing the bottle containing the stock solution of sodium bicarbonate allowed CO2to evaporate leaving sodium carbonate in the vial with a pH of 11. This solution was diluted 1 in 10 with mepivacain. The injections were painless and the necroses only were detected after three days when the bandages were removed. Discussion: Risks are inherent to even small changes of remedies. Conclusion: Home-made solutions must meet pharmaceutical standards in order to guarantee safety.