PPEH
Page 180
To minimize the risk of vomiting and to speed gastric emptying, an anti-vomiting ('anti-emetic') drug can be taken as a single dose. Alternatively the drug can be taken for a set period of time before the consumption of the lethal drug.
Page 182
The usual regime is to take 3 x 10mg tablets (30mg) about an hour before the planned ingestion of the lethal drug. An alternative form of administration is to take the drug for 48 continuous hours prior to the planned death at the usual 1 tablet (10mg) every 8 hours (ie x3 per day).
Note - this regime removes the nees to synchronise the taking of the metoclopramide with the taking of the lethal drug. It also serves to uncover any possible adverse effects of the drug leaving time enough to seek an alternative, if neccessary.
Five Last Acts
Page 561
Althought there are very few side-effects with domperidone, a person might want to experiment first if using other drugs such as metoclopramide (Experimenting using a therapeutic dose). This is especially recommended if you are thinking of beginning the anti-emetics 24 or 48 hours beforehand, as some people do.
Page 562
The onset of action for metoclopramide is from 1/2 hour to 1 hour.
The time to maximum blood concentration is less than 1 hour.
The elimination half-lives for metoclopramide is 4 to 6 hours.
The duration of action ist estimated at 1 to 2 hours.
Page 282
The exact choice and number of anti-nausea drugs is far less crucial than using common sense. Ideally you would take an initial dose a couple of hours before the self-deliverance drugs and a further dose about twenty minutes before taking lethal drugs. You would increase the normal dose slightly, but not excessively. Some people will start the anti-nausea tablets a couple of days beforehand, at the normal dosage (Usually two every eight hours) to be on the safe side. This gets them into the system well ahead of the self-deliverance.
Guide to Self Chosen and Humane Death
Page 27
Dose prior to self-chosen death: Over a period of 36 hours, every 6 to 8 hours take one tablet of 10mg or a suppository of 20mg. This medicine is recommended as the most effective anti-emetic.
Page 29
It is important to begin using metoclopramide, domperidone or cisapride at least 36 hours before carrying out a humane ending of one's life. A tablet or suppository should be taken every 6 to 8 hours. The last tablet should be taken one hour before the planned ingesting of the drug.
Suicide and Attempted Suicide
Page 257
Many drugs cause vomiting in overdose. To limit this, you can eat lightly and take one to four antinausea/travel sickness tablets about an hour before the main event.
Lostallhope
It is also worth taking up to four anti nausea tablets before drug ingestion, or perhaps better, taking them in their standard dose for around two days beforehand.
Wikibooks
Regimen
Wiki author best option: Take 15 mg Metoclopramide every 8 hours, i.e. 3 times per day, starting 48 hours in advance. Take the last dose Metoclopramide 45-60 min prior to cocktail ingestion along with 8-16 mg Ondansetron.
Dr. Admiral's best option: Take 10 mg Metoclopramide every 8 hours, i.e. 3 times per day, starting at least 36 hours in advance. Take the last dose of Metoclopramide 45 min before the drug ingestion.
Stat dose
Wiki author best option: 45 min prior to drug ingestion, take 40 mg Metoclopramide and 8-16 mg Ondansetron
Dignitas' procedure as per their webpage: 30 min prior to drug ingestion, take 20-30 mg liquid Metoclopramide.