How long after a single 4 mg dose of Adderall (mixed amphetamine salts) will a 130‑lb (≈59 kg) healthy adult female test negative on a urine amphetamine drug screen?

Detection Time for 4 mg Adderall in a 130-lb Female

A single 4 mg dose of Adderall will typically fall below the standard urine drug screen detection threshold (500 ng/mL) within 24–48 hours in a 130-lb (59 kg) healthy female, though individual variation exists.

Key Pharmacokinetic Considerations

The detection window depends on several critical factors that influence amphetamine elimination:

Dose-Dependent Excretion

• The 4 mg dose is extremely low compared to the therapeutic doses studied in the literature. Published research examined 20 mg single doses of Adderall, which produced peak urine concentrations of 2,645–5,948 ng/mL and remained detectable above 500 ng/mL for up to 47.5 hours 1.
• A 4 mg dose represents only 20% of the studied dose, suggesting proportionally lower peak concentrations (estimated 500–1,200 ng/mL) and a substantially shorter detection window 1.

Standard Detection Thresholds

• Most workplace and clinical urine drug screens use an immunoassay cutoff of 1,000 ng/mL for initial screening, with GC-MS confirmation at 500 ng/mL 1, 2.
• Using the 1,000 ng/mL screening cutoff, amphetamine is typically detectable for up to 5 days after intake at therapeutic doses; at the lower 300 ng/mL cutoff, detection extends one additional day 2.
• For a 4 mg dose, the initial concentration may barely exceed or not even reach the 1,000 ng/mL screening threshold, potentially resulting in a negative screen within 12–24 hours 1.

Individual Variability Factors

Body weight and volume of distribution:

• At 130 lb (59 kg), this individual has a relatively low body weight, which could result in slightly higher initial drug concentrations compared to heavier individuals, but the effect is modest 1.

Urinary pH (critical factor):

• Amphetamine elimination is highly pH-dependent. Acidic urine (pH < 6) dramatically accelerates amphetamine excretion, while alkaline urine (pH > 7) prolongs it 1, 3.
• Drug concentration profiles show extreme variability within and between subjects due to fluctuations in urine pH and dilution 1.

Renal clearance:

• Amphetamine has active renal excretion with a mean renal clearance of 175 ± 102 mL/min, contributing to relatively rapid elimination 4.

Terminal elimination half-life:

• The mean urinary terminal elimination half-life for amphetamine is approximately 20.7 ± 7.3 hours, though this varies considerably 4.

Practical Clinical Interpretation

Expected Timeline for 4 mg Dose

• 12–24 hours post-dose: Most likely below detection threshold for standard immunoassay screening (1,000 ng/mL) 1, 2.
• 24–48 hours post-dose: Virtually certain to be below GC-MS confirmation threshold (500 ng/mL), even accounting for individual variation 1, 2.
• Beyond 48 hours: Undetectable by any standard urine drug screening method 1, 2.

Important Caveats

Adderall contains both d- and l-amphetamine enantiomers (3:1 ratio):

• Not all immunoassays detect both enantiomers equally, and some samples containing ≥500 ng/mL total amphetamine may test negative on immunoassay due to differential cross-reactivity 1, 3.
• The presence of l-amphetamine distinguishes Adderall from pure d-amphetamine formulations (Dexedrine) and most illicit amphetamine 1, 3.

Hydration status matters:

• Dilute urine can reduce drug concentrations below detection thresholds even when drug is still being excreted 1.
• Conversely, concentrated urine may prolong apparent detection time 1.

First-void morning urine:

• The first morning urine specimen typically has the highest drug concentration and longest detection window 5.

Bottom Line

For a 130-lb female taking a single 4 mg Adderall dose, expect the urine drug screen to be negative within 24–48 hours, with most individuals testing negative by 24 hours given the very low dose. This assumes normal renal function, typical urine pH, and standard detection thresholds. If precise timing is legally or clinically critical, request quantitative GC-MS testing rather than relying on qualitative immunoassay screening 1, 3.