Ibogaine is a tryptamine. So are these:

Bufotenin, Serotonin, DMT, Melatonin, Psilocybin, Psilocin, Sumatriptan, Zolmitriptan

Not only is it a potent serotonin agonist, though, like the other drugs here (all of which are hallucinogenics or migraine drugs), it also antagonizes NMDA and agonizes kappa-opioid receptors.

Methadone, which is used as a heroin replacement, also antagonizes NMDA receptors.

Several opioid drugs, like butorphanol, levallorphan (used to counteract respiratory depression induced by opioid analgesics), nalbuphine, and pentazocine agonize kappa-opioid receptors. Kappa-opioid agonists have been investigated in addiction treatments.

All of this combines to create a drug that alleviates the symptoms of opioid withdrawal while having a hallucinogenic quality similar to substances like LSD or MDMA, which have been investigated in the context of talk therapy and which are serotonin agonists.

Basically, ibogaine seems to be used in this context for heroin addicts the same way MDMA is for people with PTSD.