flushing, hyperreflexia, dizziness, disorientation, and myoclonus. Serotonin syndrome may
theoretically occur with any drug that affects the serotonin system. However, Iovieno et al.
report that serotonin syndrome has never been reported in humans in association with 5-
HTP, either as monotherapy or in combination with other medications, including TCAs,
MAOIs and tryptophan (citing Alino et al., 1976; Das et al., 2004; Kline and Sacks, 1980;
Nardini et al., 1983; Nicolodi and Sicuteri, 1996; & Quadbeck et al., 1984).^8 Alino et al.
specifically found therapeutic efficacy in augmenting MAOIs with 5-HTP. This list is
incomplete. The Natural Standard does not review tryptophan or 5-HTP.
- SIDE EFFECTS: The most common adverse effects reported by Iovieno et al. are
gastrointestinal and include nausea, vomiting, and diarrhea. Lake and Spiegel also caution
that 5-HTP may cause sedation. Generally, oral doses of 200–300 mg per day of 5-HTP have
been well tolerated. Gastrointestinal effects are usually moderate and often abate or
disappear once a steady dosage is achieved, and Lake and Spiegel recommend an enteric
coating to minimize gastrointestinal side effects. A study comparing 5-HTP to 5-HTP plus a
peripheral decarboxylase inhibitor (PDI) found that gastrointestinal side effects were dose-
dependent and occurred more frequently in patients receiving 5-HTP alone. Less common
side effects may also include headache, insomnia, and palpitations. Available studies have
shown no sign of toxicity.^9 5 - HTP has not been studied in children or in pregnant or breast-
feeding women. Accordingly, although there are no contraindications, it cannot be
recommended.
- CONTAMINATION:
Contaminated tryptophan caused an epidemic of eosinophilia-myalgia syndrome (EMS)
that peaked in 1989. More than 1500 cases were reported by 1998, including 27
deaths. Most patients had arthralgia (73%), rash (50%), cough or dyspnea (59%),
peripheral edema (59%) elevated aldolase levels (46%) and elevated liver function tests
(43%). Neuropathy or neuritis was seen in 27%.
