4.16.1 Fatal or Dangerous Interactions




DXM should not be used (either recreationally or at normal dosage levels) by people who are taking a monoamine oxidase inhibitor (MAOI, rhymes with "wowee" - either a prescription MAOI or a recreational one such as harmaline. Note that there is considerable confusion among drug users about what is and isn't a MAOI. MAOIs include a few drugs prescribed for depression and Parkinson's disease, and a few rare recreational drugs derived from exotic plant sources (harmine and harmaline, from Syrian Rue and Yagé, for example). ProzacTM, MDMA, cheese, beer, SeldaneTM, etc., are not MAOIs - they are things to avoid when taking a MAOI. If you are taking a prescription MAOI you will almost certainly know, as your physician will have (hopefully!) told you to avoid eating aged cheeses. Combining DXM and a MAOI has been fatal (3)!

Fluoxetine (ProzacTM) is a cytochrome P450-2D6 inhibitor (39) and will change the characteristics of a DXM trip somewhat, increasing the ratio of DXM to DXO. Other P450-2D6 inhibiting drugs, which include many antidepressants, will probably do the same; see Section 15.1. The duration of the trip may be greatly extended by P450-2D6 inhibitors; some users have reported effects lasting 12 to 24 hours past the normal duration. The potency of DXM may also be enhanced via other mechanisms by fluoxetine (40).

Combining DXM with the antidepressants Desyrel (trazodone) or Serzone (nefazodone) has been reported to cause liver damage!

One user reported that combining DXM with bupropion (Wellbutrin[tm]) resulted in a prolonged (3+ day) hangover and an increase in adverse side effects.

Fluoxetine and other SSRI antidepressants, as well as tricyclics and lithium (and of course MAOIs) may interact with DXM to cause serotonin syndrome (see Section 6.2.9). This condition, although rarely fatal, is not terribly pleasant. Vascular disease may increase the chance for serotonin syndrome with DXM + antidepressants (364), and other disease conditions may do so as well. Some DXM users who have taken DXM while on antidepressants have reported unpleasant reactions that sound a lot like serotonin syndrome, so you might want to watch out. Some of the symptoms of serotonin syndrome include muscle rigidity, confusion, diarrhea, incoordination, low-grade fever, sweating, muscle tremor, mania, agitation, exaggerated reflexes, and nausea.

Do not take DXM with the diet drugs phentermine, fenfluramine, or phen-fen; this combination can also cause serotonin syndrome.

DXM should not be taken (recreationally or at normal dosage levels) with the prescription antihistamine terfenadine (SeldaneTM). This combination has been fatal (41). Terfenadine has been implicated in other drug interactions, incidentally. The reason for this interaction seems to be that terfenadine, which is normally metabolized by a P450 enzyme, induces heart irregularities when it builds up. DXM may saturate the P450 enzymes that normally metabolize terfenadine. Incidentally, this probably applies to other non-drowsy antihistamines, such as ClaritinTM and HisminalTM as well; avoid combining them with DXM.

Some people find that nicotine (cigarettes) causes severe nausea when combined with DXM. Others have noticed a general increase in physical discomfort and "bad trips" from combining the two. Some research has suggested that cigarette smoke inhibits monoamine oxidase (378,379) in which case cigarettes could greatly increase the chance of unpleasant side effects.

https://www.erowid.org/c...al_info.shtml#toc.4.16.1

It is true that DXM can interact with irreversible MAOIs. But you can't extrapolate to a reversible MAOI. The main problem with irreversible MAOIs is that they can achieve very high levels of MAO inactivation, especially when given chronically. With reversible MAOIs, occupation of CNS MAO doesn't usually exceed 50% when reasonable doses are taken (ie, below the overdose level), and occupation would be much lower after 24-48 h. The reason why ayahuasca is effective is because the point is to inhibit MAO in the gut and liver, and that is where the highest concentration of beta-carbolines would occur after ingestion of ayahuasca.