There are several ways of increasing the effectiveness of the sodium nitrite drink. Of these, use of a B blocker is considered most effective.
An effective and peaceful death is dependant on the nitrite overwhelming the restorative enzyme methemoglobin reductase. To achieve this, rapid gut absorption of the salt on ingestion is needed. This can be facilitated by fasting for several hours before taking nitrite, and by reducing the amount of gastric acid in the stomach.
A pre-dose of the H2 antagonist cimetidine can increase absorption of the nitrite (eg. Tagamet, 800mg, taken 40 minutes before the nitrite). This can be taken at the same time as the suggested anti-emetic (3 x 10mg of metoclopramide).
Tagamet, used for heartburn and indigestion, is generally unregulated, and can usually be purchased over the counter.
The lethality of nitrite can further be enhanced by the concurrent use of a B-blocker like propranolol. 800mg (10 x 80mg tablets) mixed with the dissolved nitrite and taken in the same drink.
Cimetidine - over the counter drug that facilitates nitrite absorbtion