There are 3 types of Chloroquine. According to a book I have for suicide you should preferably use Chloroquine phosphate or Chloroquine sulfate. Hydroxychloroquine sulphate is an alternative option. The book also says that a benzodiazepine is not an antidote.
According to this book:
"The letal dose is: 8 - 17 g of Chloroquine phosphate or 11 g of Chloroquine sulfate or 12 - 15 g of Hydroxychloroquine sulphate
taken together with an long acting benzodiazepine such 500 mg of Diazepam or 1000 mg of an short acting benzo (Midazolam or Lorazepam)
+ an antiemetic.
Start taking 10 mg of an antiemetic 24 hours before, every 6 hours. Last 10 mg 1 hour before taking Chloroquin and Diazepam.
Pulverize the letal drugs. You can do this one day before.
Stop eating 12 hours before taking the letal drugs. Drinking is allowed.
Mix the pulverized lethal drugs with some yogurt, pudding or fruit puree. Pepare 1-2 glasses of water.
Eat the mixture and drink 1-2 glasses of water."