How Will Taking 5-HTP Supplements Affect Existing Treatments?
Although there have been over 100 clinical studies concerning the effects of 5-HTP on the human body, none have been deemed credible in determining who should and should not take 5-HTP. The following warnings are provided from a variety of sources, based on the basic principles of the body's various system functions and what is known about the listed medications and diseases. I cannot stress enough how important it is for anyone considering taking 5-HTP supplements to speak with a licensed physician to evaluate it's benefits and risks on an individual basis.

Drug Interactions - IMPORTANT - PLEASE READ!!!
If you take one of the medications marked with an asterisk (*), you should not consume 5-HTP supplements, in any quantity, until you have discontinued the prescription drug for more than two weeks! Taking both the supplement and the medication can cause serious, and possibly permanent, life-altering results or even death! All other medications listed can cause conditions that are moderate to severe but treatable. Again, consult your prescribing physician to discuss interactions if you take any medications, including both over-the-counter and prescription drugs.
To stay as inclusive as possible, each group is alphabetized by the generic drug name, followed by the most common brand names in parentheses.

Prescription Medications
* MAO-i (Monoamine oxidase inhibitor) medications:
Benmoxin (Nerusil, Neuralex)Brofaromine (Consonar)
Caroxazone (Surodil, Timostenil)Echinopsidine (Adepren)
Furazolidone (Furoxone, Dependal-M)Hydralazine (Apresoline)
Iproclozide (Sursum)Isocarboxazid (Marplan)
Isoniazid (Laniazid, Nydrazid)Lazabemide (Pakio, Tempium)
Linezolid (Zyvox, Zyvoxam, Zyvoxid)Mebanazine (Actomol)
Metralindole (Inkazan)Minaprine (Cantor)
Moclobemide (Aurorix, Manerix) Nialamide (Niamid)
Octamoxin (Ximaol, Nimaol) Pargyline (Eutonyl)
Phenelzine (Nardil, Nardelzine)Pheniprazine (Catron)
Phenoxypropazine (Drazine)Pirlindole (Pirazidol)
Pivalylbenzhydrazine (Tersavid)Procarbazine (Matulane, Natulan, Indicarb)
Rasagiline (Azilect)Safrazine (Safra)
Selegiline (Deprenyl, Eldepryl, Emsam)Toloxatone (Humoryl)
Tranylcypromine (Parnate, Jatrosom)
Iproniazid (Marsilid, Iprozid, Ipronid, Rivivol, Propilniazida)

*SRI (Serotonin reuptake inhibitor) medications:
Citalopram (Celexa, Cipramil)Desvenlafaxine (Pristiq)
Duloxetine (Cymbalta)Escitalopram (Lexapro, Cipralex, Seroplex, Lexamil)
Fluoxetine (Prozac, Sarafem, Symbyax)Fluvoxamine (Luvox)
Milnacipram (Ixel)Paroxetine (Paxil, Aropax)
Sertraline (Zoloft)Venlafaxine (Effexor)

*T/TeCA (Tri- and Tetra-cyclic antidepressant) medications:
Amitriptyline (Elavil, Endep)Amoxapine (Asendin)
Clomipramine (Anafranil)Desipramine (Norpramin)
Doxepin (Adapin, Sinequan)Imipramine (Tofranil)
Maprotiline (Deprilept, Ludiomil, Psymion)Mazindol (Mazanor, Sanorex)
Mianserin (Bolvidon, Norval, Tolvon)Mirtazapine (Remeron, Avanza, Zispin)
Nortriptyline (Pamelor, Aventyl, Noritren)Protriptyline (Vivactil)
Setiptiline (Tecipul)Trimipramine (Surmontil)

NRI, NDRI, and NDDI (Norepinephrine/Norepinephrine-dopamine reuptake inhibitor/disinhibitor) medications:
Agomelatine (Valdoxan, Melitor, Thymanax)Atomoxetine (Strattera)
Bupropion (Wellbutrin, Zyban)Mazindol (Mazanor, Sanorex)
Reboxetine (Edronax)Viloxazine (Vivalan)

Antiparkinson medications:
Carbidopa (Lodosyn)Levodopa (Sinemet, Parcopa, Atamet, Stalevo, Madopar, Prolopa)

Triptans (Migraine treatment) medications:
Almotriptan (Axert, Almogran)Eletriptan (Relpax)
Frovatriptan (Frova, Migard, Frovamig)Naratriptan (Amerge, Naramig)
Rizatriptan (Maxalt)Sumatriptan (Imitrex, Imigran, Cinie, Illument, Migriptan)
Zolmitriptan (Zomig)

Tramadol (Fibromyalgia/pain-relief) medications:
in US - Ryzolt, Tramadol, Ultram
in UK - Dromadol, Tramake, Zamadol, Zydol in Australia - Tramahexal, Tramal, Zydol
in Germany - Tramadolor, Tramal
in France - Contramal, Ixprim, Topalgic, Tramadol, Zamudol
in Mexico - Nobligan, Sinergix, Tradol, Tramacet, Trexol, Veldrol, Zaldair
(for Brand names of Tramadol in other countries, please visit the Wikipedia list)

Other Drug and Chemical Reactions
Over-the-counter cough suppressant ingredients:
Dextromethorphan (Benylin, Buckley's, Delsym, Pediacare, Pertussin, Robitussin, Sucrets, Triaminic, Vicks, etc.)

Over-the-counter and prescription-strength insomnia and/or sleep aid medications:
Zolpidem (Adormix, Ambien, Edluar, Zolpimist, Damixan, Hypnogen, Ivedal, Lioran, Myslee, Nasen, Nytamel, Sanval, Somidem, Stilnoct, Stilnox, Sucedal, Zodorm, Zoldem, Zolnod, Zolpihexal)

Recreational, illegal, and street drugs:
*THC, or tetrohydrocannibinol (marijuana)
*BZME, or benzoylmethylecgonine (cocaine, crack-cocaine, novocaine)
*Methamphetamine, used as an illegal/recreational street drug but also prescribed for ADHD (meth, Desoxyn)
*Opiates and Opiods:
DAM, or diacetylmorphine (Heroin is the name of both the street drug and the prescription drug)
DHC, or dihydrocodeinone and its derivatives (Hydrocodone, Vicodin, Hydrococet, Symtan, Anexsia, Damason-P, Dicodid, Hycodan, Hydromet, Hycomine, Hycet, Lorcet, Lortab, Norco, Novahistex, Hydrovo, Duodin, Kolikodol, Orthoxycol, Panacet, Zydone, Mercodinone, Synkonin, Norgan, Xodol, Hydrokon, Oxycodone, OxyContin, OxyNorm, Oxy-IR, Percocet, Depalgos, Percodan, Proladone, Eukodol, Eucodol, Roxicodone, Tylox, Percudan-Demi, Hydromorphone, Morphine, MS Contin, MSIR, Avinza, Kadian, Oramorph, Roxanol, Kapanol, Dilaudid, Palladone)

Conflicting Conditions or "Contraindications"
The term "contraindications" appears a lot when you're researching 5-HTP (or any other chemical/nutritional supplement). What it means, in layman's terms, is that taking 5-HTP supplements is not advised if you currently have one or more of the following conditions. Any listed condition with an asterisk (*) next to its name has significant conflicts with 5-HTP supplements and you should not, under most circumstances, take the supplement if you suffer from these. If you have any of the others on this list then you should talk to the physician in charge of treating your condition to determine how 5-HTP supplements will affect you.

*Cardiovascular Disease (Heart Disease, Atherosclerosis, Coronary Artery Disease, etc.) - elevated levels of serotonin can contribute to heart concerns, mainly heart valve damage or the disease called cardiac fibrosis. If you suffer from any cardiovascular (heart) disease, 5-HTP may significantly increase the effects or symptoms of the disease.

*Urinary/Renal Disease (Kidney Disease, Renal Failure, etc.) - serotonin slightly increases the levels of urinary chemicals in the body. Serotonin excess filters through the kidneys to be eliminated as urine. If you suffer from a urinary dysfunction or renal (kidney) disease, taking 5-HTP may cause a significant increase in the condition's symptoms, which could be life-threatening.

*Liver Disease (Hepatitis, Cirrhosis, etc.) - since the liver helps process 5-HTP into serotonin, compromised liver function can worsen or fail when 5-HTP supplements are taken.

*Immune Deficiency/Disorder (HIV, AIDS, Rheumatoid Arthritis, Multiple Sclerosis, Lupus, etc.) - 5-HTP can be lethal if the body's immune system is compromised by these conditions. The immune system tells the body which incoming substances are harmful and to 'attack' them if they pose a threat. Auto-immune disorders and immune deficiencies prevent the body from distinguishing the good from the bad so 5-HTP will not be used properly and will, likely, contribute to complications from these conditions.

Gastrointestinal Disorder (Irritable Bowel Syndrome, Gastric-Bypass Syndrome, Pyloric Disorder, Gastritis, etc.) - the body metabolizes leftover/unused serotonin and eliminates it from the digestive system, which contributes to weight loss. In individuals suffering from gastrointestinal disorders, including eating disorders like anorexia nervosa and IBS (irritable bowel syndrome), may experience debilitating effects when they take 5-HTP supplements.

Blood Disorder (Hemophilia, Anemia, etc.) - blood disorders prevent the components (platelets, plasma, cells, etc.) from doing their specified jobs. When serotonin or melatonin enters the blood stream, it may get 'lost' or be misused by the blood's components. Although this will usually result in no benefits from the supplement, it may also cause moderate to severe issues in the body over time.

*Pregnancy and Nursing (or the possibility of becoming pregnant) - no studies or clinical trials have been conducted to determine the effects of 5-HTP on developing embryos/fetuses when taken by women who are pregnant. Given how critical proper gestation is for embryonic and fetal development, and considering the nature of 5-HTP processes in the body, the use of this supplement by women who are pregnant or nursing is potentially dangerous to the child.

Disclaimer: These simplified explanations are based on my understanding of the medical and chemical terms and processes after extensive research. I have made every effort to investigate each word, reaction, process, etc. to the greatest extent. I am, by no means, an expert in either the medical or chemistry fields of study. Please feel free to consult an expert or conduct your own research for verification of any statement on this site.

ATTENTION MEDICAL AND CHEMISTRY PROFESSIONALS: If I have misinterpreted, misstated, and/or misrepresented any of the details of tryptophan and/or 5-HTP processes or definitions in relation to human physiology, PLEASE provide me with the correct information so I can update the statements on this site. Thanks!