MAOIs Dextromethorphan

Many commonly used medications also contain substances that are eliminated by the MAOIs and must not be taken by these patients. The list of medications to be avoided inclndes the narcotic pain reliever meperidine (Demerol), and many over-the-connter cold remedies containing dextromethorphan or pseudoephedrine. Finally, patients taking MAOIs must also avoid medications that elevate serotonin levels. This inclndes certain appetite snppressants and antidepressants including the SSRIs, venlafaxine, duloxetine, mirtazapine, nefazodone, and trazodone. Medications that interact with the MAOIs cannot be taken until at least 2 weeks after the MAOI has been stopped. 

Dextromethorphan (Mediquell, Benylin DM, PediaCare 1, Delsym, Others) [OTC] [Antitussive] Uses Control nonproductive cough Action Suppresses medullary cough center Dose Adults. 10-30 mg PO q4h PRN (max 120 mg/24 h) Peds. 2-6 y 2.5-7.5 mg q4-8h (max 30 mg/24 h) 7-12 y 5-10 mg q4-8h (max 60 mg/24/h) Caution [C, /-] Not for persistent or chronic cough Contra < 2 y. Disp Caps, lozenges, syrup, Liq SE GI disturbances Interactions T Effects W/ amiodarone, fluoxetine, quinidine, terbinafme T risk of serotonin synd Wf sibutramine, MAOIs T CNS depression Wf antihistamines, antidepressants, sedative, opioids, EtOH EMS Will not affect cough caused by asthma,... 

Uses Obesity Action Blocks uptake of norepinephrine, serotonin, dopamine Dose 10 mg/d PO, may to 5 mg after 4 wk Caution [C, -] w/ SSRIs, Li, dextromethorphan, opioids Contra MAOI w/in 14 d, uncontrolled HTN, arrhythmias Disp Caps SE HA, insomnia, xerostomia, constipation, rhinitis, tach, HTN Interactions T Risk of serotonin synd W/ dextromethorphan, ergots, fentanyl, Li, meperidine, MAOIs, naratriptan, pentazocine, rizatriptan, sumatriptan, SSRIs, tryptophan, zolmitriptan, St. John s wort effects W/ cimetidine, erythromycin, ketoconazole T CNS depression W/ EtOH EMS Use fentanyl w/ caution, may T risk of serotonin synd concurrent EtOH use can T CNS depression OD May cause tach, HTN, diaphoresis, HA, fever, agitation, muscle tremors, and Szs symptomatic and supportive... 

Dmg-induced serotonin syndrome is generally mild and resolves when the offending drugs are stopped. However, it can be severe and deaths have occurred. A large number of drugs have been implicated including tricyclic antidepressants, monoamine oxidase inhibitors (MAOIs), selective serotonin re-uptake inhibitors (SSRIs), pethidine, lithium, and dextromethorphan. The most severe type of reaction has occurred with the combination of selective serotonin re-uptake inhibitors and monoamine oxidase inhibitors. Both non-selective MAOIs such as phenelzine and selective MAOIs such as moclobemide and selegiline have been implicated. 

Medications with serotonergic activity may also have other monaminergic or sympathomimetic activity. Combining MAOIs with these medications may result in a complex side effect profile. For example, combining meperidine or dextromethorphan with MAOIs may result in respiratory depression, in addition to symptoms of serotonin excess. Furthermore, interactions between MAOIs and tricyclic antidepressants (TCAs) more commonly result in potentiating shared adverse events such as othostatic hypotension, as opposed to hyperadrenergic crises or the serotonin syndrome. 

Patients should not use dextromethorphan if they are taking any drug in the class known as monoamine oxidase inhibitors (MAOI), including phenelzine (Nardil), isocarboxazid (Marplan), and tranylcypromine (Parnate), which are used in the treatment of depression. The combination of MAOIs with dextromethorphan can lead to toxic levels of dextromethorphan in the blood. 

MAOIs PETHIDINE, MORPHINE, PHENOPERIDINE, DEXTROMETHORPHAN Two types of reaction are reported 1. Risk of serotonin syndrome with dextromethorphan, pethidine or tramadol and MAOIs 2. Depressive - respiratory depression, hypotension, coma Type 1 reactions are attributed to inhibition of reuptake of serotonin -more common with pethidine, phenoperidine, dextromethorphan. Type II reactions are attributed to MAOI inhibition of metabolism of opioids - more common with morphine Avoid co-administration do not give dextromethorphan, pethidine or tramadol for at least 2 weeks after cessation of MAOI... 

Drug interactions serotonin syndrome includes diaphoresis, rigidity, myoclonus, hyperthermia, ANS instability, and seizures. Has been reported for SSRIs when used with MAOIs, TCAs, meperidine, and dextromethorphan. 

The anticholinergic effect of opiates (including OTC cough preparations containing dextromethorphan) would synergize with the actions of catecholamines produced by the MAOI. This could result in heart failure. 

Dextromethorphan (Robitussin) interacts with MAOIs to produce hypertension, fever, and coma. This statement warrants intervention. 

Because sibutramine inhibits serotonin uptake, and because the serious serotonin syndrome has been seen when serotonergic drugs were taken with SSRIs, the manufacturers say that sibutramine should not be taken with any serotonergic drugs. They name dextromethorphan, dihydroergot-amine, fentanyl, pentazocine, pethidine (meperidine), SSRIs, sumatriptan, and tryptophan. Possible cases have been reported for sibutramine and SSMs , (below).The US manufacturers also include lithium in their list. Note that this list is not exhaustive (see MAOIs under (d) above) and a case of the serotonin syndrome has been seen when venla-faxine was given with sibutramine. ... 

In a study in 14 healthy subjects, two 20-mg doses of dextromethorphan given 4 hours apart, before and during the use of linezolid 600 mg every 12 hours, had no effect on linezolid pharmacokinetics. The AUC and maximum level of the dextromethorphan metabolite, dextrorphan was decreased by 30%, but this was not considered sufficient to warrant any dosing alterations. There was no evidence of the serotonin syndrome, as measured by changes in body temperature, alertness and mental performance. However, the manufacturers describe one case where the concurrent use of linezolid and dextromethorphan resulted in the serotonin syndrome. Linezolid has mild reversible MAOI activity, and the serotonin syndrome has been described when dextromethorphan was taken by patients also taking antidepressant MAOIs, see MAOIs or RIMAs + Dextromethorphan , p.l 134. If the concurrent use of linezolid and dextromethorphan is considered necessary, it would seem prudent to monitor for symptoms of the serotonin syndrome , (p.9). 

The manufacturer of rasagiline su ests that its use with dextromethorphan should be avoided. Similarly, some consider that patients taking selegiline should try to avoid dextromethorphan. These warnings are based on the serious adverse reactions (the serotonin syndrome or similar) that have rarely occurred when dextromethorphan has been used with non-selective MAOIs or RIMAs , (p.ll34). The likelihood of any interaction with MAO-B... 

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