The short answer
This is a labeled interaction. The EVEKEO amphetamine sulfate label names glutamic acid HCl among gastrointestinal acidifying agents that reduce amphetamine absorption, blood levels and effectiveness. It gives no supplement dose threshold, effect size or separation interval. No human study of the exact combination was identified in the reviewed searches. Discuss the product with your prescriber or pharmacist before starting or stopping it.
What this answer covers
L-glutamic acid hydrochloride, the acidic hydrochloride salt used as a gastric acidifier, taken by mouth with oral amphetamine sulfate as EVEKEO tablets or as one of the four salts in ADDERALL and ADDERALL XR. Plain L-glutamic acid and monosodium glutamate are different products and are outside this scope.
- Supplement or preparation
- L-glutamic acid hydrochloride
- Medication ingredient
- amphetamine sulfate
The label names this ingredient
The EVEKEO label lists glutamic acid HCl among gastrointestinal acidifying agents that lower the absorption of amphetamines, and states that such agents lower blood levels and how well amphetamines work. That is an unusually specific naming: most of the interaction entry is written as a class, and this ingredient is one of the few named examples.
The same class statement appears on the mixed salt labels
The ADDERALL XR label says agents that alter urinary pH change amphetamine blood levels, and both ADDERALL labels direct the prescriber to increase the dose based on clinical response when an acidifying agent is used. The current ADDERALL tablet label has replaced its named examples with the categories gastrointestinal acidifying agents and urinary acidifying agents, so it supports the class effect without naming this ingredient.
What is known about the size of the effect
No human study measuring this combination was identified in the reviewed searches. Studies of amphetamine under altered urinary pH and reviews of urinary acidifiers provide indirect context, but they do not measure the gastrointestinal effect named in the EVEKEO label. They therefore cannot quantify how a glutamic acid hydrochloride supplement would affect amphetamine exposure or response.
What to do
Check the supplement label for glutamic acid hydrochloride or glutamic acid HCl, since plain L-glutamic acid is a different ingredient. Tell your prescriber and pharmacist about the product and any change in how well the medicine works. ADDERALL labeling describes clinician-directed dose adjustment for acidifying agents, while EVEKEO gives the interaction warning without a specific adjustment instruction. Do not change the stimulant dose yourself. No supported separation interval was identified; ask your pharmacist to review the full regimen.
Evidence and practical considerations
Absorption & effectiveness
Current amphetamine sulfate labeling names glutamic acid HCl among the gastrointestinal acidifying agents that lower absorption of amphetamines and lower blood levels and efficacy. The direction is labeled and specific to this ingredient, but no dose, effect size or study supports the magnitude.
- Exact scope
- L-glutamic acid hydrochloride, the acidic salt; plain L-glutamic acid and glutamate salts are outside this finding. with Oral amphetamine sulfate, both as the single-entity tablet (EVEKEO) and as one of the four salts in mixed amphetamine salts products (ADDERALL tablets and ADDERALL XR capsules).
- Medication form and route
- oral medication; oral supplement
- Timing or duration
- While both are taken; no onset, offset or separation interval is established by the inspected sources
What remains uncertain
- Label-based warning: the named salt does not specify stereochemistry. No exact-pair human study was identified, and no dose threshold or effect size is stated. The current mixed-salt tablet label uses a class statement rather than the named example.
Factors that may matter: Dose of the hydrochloride salt; Whether it is taken with the stimulant dose; Amphetamine release form; Other acidifying or alkalinizing products.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 22, 2026
Population: People prescribed amphetamine sulfate
The Drug Interactions section names glutamic acid HCl among gastrointestinal acidifying agents that lower absorption of amphetamines, alongside guanethidine, reserpine, ascorbic acid and fruit juices, and states that these agents lower blood levels and efficacy of amphetamines.
How this applies: Exact amphetamine sulfate (RxCUI 81952) as the single active ingredient of this label; the interaction section names the supplement ingredient itself rather than a drug class only.
The label names glutamic acid HCl without specifying stereochemistry. It gives no supplement dose threshold, effect size or separation interval and cites no exact-pair study.
Source 2: current product label
dailymed.nlm.nih.gov · Source check Sep 22, 2026
Population: People prescribed amphetamine sulfate
Section 2.7 states that agents which alter urinary pH affect excretion and alter blood levels of amphetamines, and the interaction table states that acidifying agents lower blood levels and efficacy and that the dose should be increased based on clinical response.
How this applies: Exact amphetamine sulfate (RxCUI 81952) as one of the four amphetamine salts in this product; the interaction statement is written for amphetamines as a group and applies to every salt in the capsule.
This label names ascorbic acid rather than glutamic acid hydrochloride, so it supports the class effect rather than this specific ingredient.
Source 3: current product label
dailymed.nlm.nih.gov · Source check Sep 22, 2026
Population: People prescribed amphetamine sulfate
The current interaction table states that acidifying agents lower blood levels and efficacy of amphetamines and directs increasing the dose based on clinical response, giving only the categories gastrointestinal acidifying agents and urinary acidifying agents as examples.
How this applies: Amphetamine sulfate (RxCUI 81952) is one of the four salts in ADDERALL immediate-release tablets. The class interaction statement applies to the mixed-salt product; it does not isolate one salt or establish the effect of every supplement.
This label no longer names glutamic acid HCl. The class statement remains, but the specific ingredient has been dropped from the examples.
Source 4: original human pharmacokinetic study
pubmed.ncbi.nlm.nih.gov · Source check Sep 22, 2026
Population: Healthy adult volunteers.
The elimination kinetics of each isomer were measured under both urine conditions. The difference in half-life between the isomers was greatest under basic urinary pH, and (+)-amphetamine was eliminated faster than the (-)-isomer.
How this applies: Human evidence about amphetamine kinetics under experimentally altered urinary pH. The abstract does not identify the acidifying or alkalinizing agents, so it does not establish the effect of any specific supplement.
Small healthy-volunteer study read as an abstract. The abstract does not give the acidifying or alkalinizing agents, their doses, or the resulting plasma concentrations, and no dietary supplement was tested.
Source 5: systematic literature review of human trials
ebi.ac.uk · Source check Sep 22, 2026
Population: Adults and children aged 6.5 to 76.5 years across 150 experiments and 2,895 participants
Across 150 human experiments on urinary pH, the most effective acidifying agents were oral ammonium chloride at minus 1.63 pH units, oral methionine at minus 0.72 and a high protein diet at minus 0.65. Glutamic acid hydrochloride was not among the tested interventions.
How this applies: Provides context on urinary acidification but includes no glutamic acid hydrochloride intervention. It does not assess the gastrointestinal mechanism specified by EVEKEO labeling.
Literature review of urinary pH studies searched through September 2023, with heterogeneous designs, populations and pH measurements. It does not test gastric acidity or amphetamine pharmacokinetics. An intervention missing from the review is not proof that no study exists.
Source 6: pharmacokinetic review
pubmed.ncbi.nlm.nih.gov · Source check Sep 22, 2026
Population: Children, adolescents and adults taking amphetamine formulations.
Oral amphetamine is rapidly absorbed with high bioavailability, immediate-release products reach peak concentration in 2 to 3 hours, and the review states that there are few documented pharmacokinetic drug interactions of clinical significance beyond the influence of drug-induced changes in urinary pH.
How this applies: Places the urinary pH mechanism in context for the marketed amphetamine products, including those containing amphetamine sulfate. It is a review rather than an original measurement.
Narrative pharmacokinetic review read as an abstract. It does not test or quantify any dietary supplement.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Editorial update | |
| Editorial source audit clarified label scope, evidence limits and practical wording. No clinical approval was recorded. | |
| Research summary published | |
| Article prepared | |
| Prepared exact amphetamine sulfate and L-Glutamic acid hydrochloride article from inspected current labeling and original sources, with uncertainty stated. |
Article revision: ae8fa732dfa5f125
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.