One of the first noticeable effects of large-dose ibogaine ingestion is ataxia, a difficulty in coordinating muscle motion which makes standing and walking difficult without assistance. Xerostomia (dry mouth), nausea, and vomiting may follow. These symptoms may be long in duration, ranging from 4 to 24 hours in some cases. Ibogaine is sometimes administered by enema to help the subject avoid vomiting up the dose. Psychiatric medications are strongly contraindicated in ibogaine therapy due to adverse interactions. Some studies also suggest the possibility of adverse interaction with heart conditions. In one study of canine subjects, ibogaine was observed to increase sinus arrhythmia (the normal change in heart rate during respiration). Ventricular ectopy has been observed in a minority of patients during ibogaine therapy. It has been proposed that there is a risk of QT-interval prolongation following ibogaine administration. This risk was further demonstrated by a case reported in the New England Journal of Medicine documenting prolonged QT interval and ventricular tachycardia after initial use.
There are 12 documented fatalities that have been loosely associated with ibogaine ingestion. Exact determinations of the cause of death have proven elusive due to the quasi-legal status of ibogaine and the unfamiliarity of medical professionals with this relatively rare substance. No autopsy to date has implicated ibogaine as the sole cause of death. Causes given range from significant pre-existing medical problems to the surreptitious consumption of other drugs in conjunction with ibogaine. Many legal and illegal psychoactive drugs and even foods or supplements such as grapefruit juice and goldenseal are strongly contraindicated immediately before, during or immediately after ibogaine treatment, which presents a risk in undersupervised or self-treating persons.