Two capsules contain: Vitamin B6 (as pyridoxine HCl) 20 mg • L-Phenylalanine 1000 mg. Other Ingredients: Cellulose (capsule shell), Magnesium Stearate, Silica, Cellulose, Calcium Silicate.
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Below is general information about the effectiveness of the known ingredients contained in the product L Phenylalanine Caps. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.
INSUFFICIENT RELIABLE EVIDENCE to RATE
INSUFFICIENT RELIABLE EVIDENCE to RATE
Below is general information about the safety of the known ingredients contained in the product L Phenylalanine Caps. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.
LIKELY SAFE ...when L-phenylalanine is consumed in amounts typically found in foods (11120).
POSSIBLY SAFE ...when L-phenylalanine is used orally in doses up to 100 mg/kg daily for up to 3 months (2463,2464,2466,2467,2469). ...when D-phenylalanine is used orally in doses up to 1 gram daily for up to 4 weeks, or as a single dose of 4-10 grams (2455,2456,2459,68795,104792). ...when DL-phenylalanine is used orally in doses up to 200 mg daily for up to 4 weeks (2468,68795,68825). ...when phenylalanine cream is applied topically, short-term (2461,92704).
PREGNANCY: LIKELY SAFE
when L-phenylalanine is consumed in amounts typically found in foods by pregnant patients with normal phenylalanine metabolism (2020,11120).
PREGNANCY: UNSAFE
when L-phenylalanine is consumed in amounts typically found in foods by pregnant patients with high serum phenylalanine concentrations, such as those with phenylketonuria (PKU).
Serum levels of phenylalanine greater than 360 micromol/L increase the risk of birth defects (1402,11468). Experts recommend that patients with high phenylalanine serum concentrations follow a low phenylalanine diet for at least 20 weeks prior to conception to decrease the risk for birth defects (1402).
There is insufficient reliable information available about the safety of L-phenylalanine when taken by mouth in large doses during pregnancy; avoid using.
There is insufficient reliable information available about the safety of oral D-phenylalanine during pregnancy; avoid using.
LACTATION: LIKELY SAFE
when L-phenylalanine is consumed in amounts typically found in foods by breast-feeding patients with normal phenylalanine metabolism (2020,11120).
There is insufficient reliable information available about the safety of L-phenylalanine when taken by mouth in medicinal amounts during lactation; avoid using. There is insufficient reliable information available about the safety of oral D-phenylalanine during lactation; avoid using.
LIKELY SAFE ...when used orally and appropriately in doses that do not exceed the tolerable upper intake level (UL) of 100 mg daily for adults (15). ...when used parenterally and appropriately. Injectable vitamin B6 (pyridoxine) is an FDA-approved prescription product (15).
POSSIBLY SAFE ...when used orally and appropriately in doses of 101-200 mg daily (6243,8558).
POSSIBLY UNSAFE ...when used orally in doses at or above 500 mg daily. High doses, especially those exceeding 1000 mg daily or total doses of 1000 grams or more, pose the most risk. However, neuropathy can occur with lower daily or total doses (6243,8195). ...when used intramuscularly in high doses and frequency due to potential for rhabdomyolysis (90795).
CHILDREN: LIKELY SAFE
when used orally and appropriately (3094).
CHILDREN: POSSIBLY SAFE
when used orally and appropriately in amounts exceeding the recommended dietary allowance (5049,8579,107124,107125,107135).
CHILDREN: POSSIBLY UNSAFE
when used orally in excessive doses, long-term (3094).
PREGNANCY: LIKELY SAFE
when used orally and appropriately.
A special sustained-release product providing vitamin B6 (pyridoxine) 75 mg daily is FDA-approved for use in pregnancy. Vitamin B6 (pyridoxine) is also considered a first-line treatment for nausea and vomiting in pregnancy by the American College of Obstetrics and Gynecology (111601). However, it should not be used long-term or without medical supervision and close monitoring.
PREGNANCY: POSSIBLY UNSAFE
when used orally in excessive doses.
There is some concern that high-dose maternal vitamin B6 (pyridoxine) can cause neonatal seizures (4609,6397,8197).
LACTATION: LIKELY SAFE
when used orally in doses not exceeding the recommended dietary allowance (RDA) (3094).
The RDA in lactating women is 2 mg daily. There is insufficient reliable information available about the safety of vitamin B6 when used in higher doses in breast-feeding women.
Below is general information about the interactions of the known ingredients contained in the product L Phenylalanine Caps. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.
Concomitant intake of phenylalanine may reduce the intestinal absorption of baclofen.
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Phenylalanine and baclofen share the same intestinal carrier for absorption; phenylalanine competitively inhibits the absorption of baclofen, reducing its plasma levels (23788).
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Phenylalanine, especially in high doses, can reduce the effectiveness of levodopa.
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Theoretically, concomitant use of L-phenylalanine and non-selective MAOIs might increase the risk of hypertensive crisis.
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L-phenylalanine is metabolized to tyrosine (2052,9949). Some evidence suggests that L-phenylalanine, given with the non-selective MAOI pargyline, might prevent the elimination of tyramine, increasing the risk of hypertensive crisis (2021). However, this was not reported in a small number of patients when using L-phenylalanine with the partially selective MAO-B inhibitor, selegiline (2469).
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Theoretically, vitamin B6 might increase the photosensitivity caused by amiodarone.
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Theoretically, vitamin B6 may have additive effects when used with antihypertensive drugs.
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Research in hypertensive rats shows that vitamin B6 can decrease systolic blood pressure (30859,82959,83093). Similarly, clinical research in patients with hypertension shows that taking high doses of vitamin B6 may reduce systolic and diastolic blood pressure, possibly by reducing plasma levels of epinephrine and norepinephrine (83091).
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Vitamin B6 may increase the metabolism of levodopa when taken alone, but not when taken in conjunction with carbidopa.
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Vitamin B6 (pyridoxine) enhances the metabolism of levodopa, reducing its clinical effects. However, this interaction does not occur when carbidopa is used concurrently with levodopa (Sinemet). Therefore, it is not likely to be a problem in most people (3046).
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High doses of vitamin B6 may reduce the levels and clinical effects of phenobarbital.
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High doses of vitamin B6 may reduce the levels and clinical effects of phenytoin.
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Below is general information about the adverse effects of the known ingredients contained in the product L Phenylalanine Caps. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.
General
...Orally, L-phenylalanine and D-phenylalanine are generally well tolerated when used in typical doses.
Most Common Adverse Effects:
Orally: Anxiety, constipation, headache, heartburn, insomnia, nausea, and sedation.
Topically: Burning, erythema, and itching.
Cardiovascular ...One patient in a small case series developed extrasystoles after 10 days of treatment with DL-phenylalanine, but this resolved on the 12th day of treatment without discontinuing phenylalanine (68825).
Dermatologic ...Topically, erythema, itching, and burning have been reported in some patients using an undecylenoyl phenylalanine 2% cream for treatment of age spots (92704).
Gastrointestinal ...Orally, constipation, heartburn, and nausea has been reported in some patients taking phenylalanine (2463,68827,68829,68830).
Neurologic/CNS
...Orally, headaches, which are typically transient and do not require treatment or dosage reduction, have been reported during the first 10 days of treatment with L-, D-, and DL-phenylalanine (68795,68825,68827,68829).
Transient vertigo has also been reported with D- and DL-phenylalanine (68795).
In patients with Parkinson disease, taking DL-phenylalanine, especially in high doses, interferes with levodopa transport into the brain, causing increased rigidity, tremor, and occurrence of the on-off phenomenon. Akinesia has been reported more rarely (3291,3292,3293,3294,68828). In patients with schizophrenia, taking a single dose of L-phenylalanine 100 mg/kg has been associated with worsening of medication-induced tardive dyskinesia (2457).
Psychiatric ...Orally, L-phenylalanine has been associated with anxiety, insomnia, and, more rarely, hypomania (68827,68829). DL-phenylalanine has been associated with fatigue and sedation (9951).
General
...Orally or by injection, vitamin B6 is well tolerated in doses less than 100 mg daily.
Most Common Adverse Effects:
Orally or by injection: Abdominal pain, allergic reactions, headache, heartburn, loss of appetite, nausea, somnolence, vomiting.
Serious Adverse Effects (Rare):
Orally or by injection: Sensory neuropathy (high doses).
Dermatologic ...Orally, vitamin B6 (pyridoxine) has been linked to reports of skin and other allergic reactions and photosensitivity (8195,9479,90375). High-dose vitamin B6 (80 mg daily as pyridoxine) and vitamin B12 (20 mcg daily) have been associated with cases of rosacea fulminans characterized by intense erythema with nodules, papules, and pustules. Symptoms may persist for up to 4 months after the supplement is stopped, and may require treatment with systemic corticosteroids and topical therapy (10998).
Gastrointestinal ...Orally or by injection, vitamin B6 (pyridoxine) can cause nausea, vomiting, heartburn, abdominal pain, mild diarrhea, and loss of appetite (8195,9479,16306,83064,83103,107124,107127,107135). In a clinical trial, one patient experienced infectious gastroenteritis that was deemed possibly related to taking vitamin B6 (pyridoxine) orally up to 20 mg/kg daily (90796). One small case-control study has raised concern that long-term dietary vitamin B6 intake in amounts ranging from 3.56-6.59 mg daily can increase the risk of ulcerative colitis (3350).
Hematologic ...Orally or by injection, vitamin B6 (pyridoxine) can cause decreased serum folic acid concentrations (8195,9479). One case of persistent bleeding of unknown origin has been reported in a clinical trial for a patient who used vitamin B6 (pyridoxine) 100 mg twice daily on days 16 to 35 of the menstrual cycle (83103). It is unclear if this effect was due to vitamin B6 intake.
Musculoskeletal ...Orally or by injection, vitamin B6 (pyridoxine) can cause breast soreness or enlargement (8195).
Neurologic/CNS ...Orally or by injection, vitamin B6 (pyridoxine) can cause headache, paresthesia, and somnolence (8195,9479,16306). Vitamin B6 (pyridoxine) can also cause sensory neuropathy, which is related to daily dose and duration of intake. Doses exceeding 1000 mg daily or total doses of 1000 grams or more pose the most risk, although neuropathy can occur with lower daily or total doses as well (8195). The mechanism of the neurotoxicity is unknown, but is thought to occur when the liver's capacity to phosphorylate pyridoxine via the active coenzyme pyridoxal phosphate is exceeded (8204). Some researchers recommend taking vitamin B6 as pyridoxal phosphate to avoid pyridoxine neuropathy, but its safety is unknown (8204). Vitamin B6 (pyridoxine) neuropathy is characterized by numbness and impairment of the sense of position and vibration of the distal limbs, and a gradual progressive sensory ataxia (8196,10439). The syndrome is usually reversible with discontinuation of pyridoxine at the first appearance of neurologic symptoms. Residual symptoms have been reported in patients taking more than 2 grams daily for extended periods (8195,8196). Tell patients daily doses of 100 mg or less are unlikely to cause problems (3094).
Oncologic ...In females, population research has found that a median intake of vitamin B6 1. 63 mg daily is associated with a 3.6-fold increased risk of rectal cancer when compared with a median intake of 1.05 mg daily (83024). A post-hoc subgroup analysis of results from clinical research in adults with a history of recent stroke or ischemic attack suggests that taking folic acid, vitamin B12, and vitamin B6 does not increase cancer risk overall, although it was associated with an increased risk of cancer in patients who also had diabetes (90378). Also, in patients with nasopharyngeal carcinoma, population research has found that consuming at least 8.6 mg daily of supplemental vitamin B6 during treatment was associated with a lower overall survival rate over 5 years, as well as a reduced progression-free survival, when compared with non-users and those with intakes of up to 8.6 mg daily (107134).