Vyvanse and Caffeine Interaction: What the Evidence Actually Shows

Does the Vyvanse label list caffeine as an interaction?

No. The drug interactions section of the current Vyvanse (lisdexamfetamine) label covers monoamine oxidase inhibitors, serotonergic drugs, CYP2D6 inhibitors, urinary alkalinizing agents, urinary acidifying agents and tricyclic antidepressants. Caffeine is not among them [1].

What the label does say is broader and directly relevant. CNS stimulants raise blood pressure by a mean of about 2 to 4 mm Hg and heart rate by a mean of about 3 to 6 bpm, some patients have larger increases, and the label says to monitor blood pressure and pulse during treatment [1]. Vyvanse is taken in the morning, and the label says to avoid afternoon doses because of insomnia [1].

What caffeine does on its own

Caffeine is a methylxanthine whose likely mechanism is blockade of adenosine receptors; the older phosphodiesterase and intracellular calcium explanations only apply at high, non-physiological concentrations [6]. Caffeine also activates noradrenaline neurons and appears to affect local dopamine release [6].

The FDA cites 400 mg a day, about two to three 12-fluid-ounce cups of coffee, as an amount not generally associated with negative effects for most adults. The same page stresses wide variation in how sensitive people are to caffeine and how fast they clear it, and notes that certain conditions and some medications increase sensitivity [5].

For children and teenagers the FDA page cites medical experts, including the American Academy of Pediatrics, advising against energy drinks. Too much caffeine in this age group can cause increased heart rate, palpitations, high blood pressure, anxiety, sleep problems and digestive problems [5]. Vyvanse is approved for ADHD from age 6 [1].

Is there a metabolic interaction?

The two are handled by different machinery. Lisdexamfetamine is an inactive prodrug converted to dextroamphetamine and l-lysine mainly in blood by red blood cells, not by cytochrome P450 enzymes [1]. Caffeine is cleared by CYP1A2, which carries out its main metabolic step, 3-N-demethylation to paraxanthine; the FDA lists caffeine as a clinical index substrate for CYP1A2 [3][7]. Less than 2% of a caffeine dose is excreted unchanged in urine [8].

The only enzyme-based interaction entry in the Vyvanse label concerns CYP2D6 inhibitors, which may increase exposure to dextroamphetamine and add to serotonin syndrome risk [1]. Caffeine is not part of that entry [1].

The two also clear at very different speeds. Reported caffeine half-life group means in healthy adults run from about 3.4 to 6.2 hours, with wide individual spread [4][9][10][11][12]. Dextroamphetamine half-life is about 10 to 11.3 hours in adults and 8.6 to 9.5 hours in children aged 6 to 12 [1].

What Vyvanse side effects does the label report?

These are the adverse reactions reported in the label's 4-week adult ADHD trial (Vyvanse 358 people, placebo 62), where the rates were at least 2% on Vyvanse and at least twice placebo: decreased appetite 27% vs 2%; insomnia 27% vs 8%; dry mouth 26% vs 3%; diarrhea 7% vs 0%; nausea 7% vs 0%; anxiety 6% vs 0%; feeling jittery 4% vs 0%; increased blood pressure 3% vs 0%; increased heart rate 2% vs 0%; palpitations 2% vs 0% [1].

The label also warns that sudden death has been reported in patients with structural cardiac abnormalities or other serious cardiac disease treated with CNS stimulants at ADHD doses. It says to avoid Vyvanse in patients with known structural cardiac abnormalities, cardiomyopathy, serious arrhythmia or coronary artery disease [1].

How much caffeine is in what people actually drink?

FDA typical values per 12 fl oz: regular brewed coffee 113 to 247 mg; black tea 71 mg; green tea 37 mg; caffeinated soft drink 23 to 83 mg; energy drink 41 to 246 mg, with energy drinks generally 54 to 328 mg per 16 fl oz [5]. Decaf coffee typically has 2 to 15 mg per 8-fl-oz cup, so it is not caffeine-free, and the FDA says the body handles natural and added caffeine the same way [5].

At the top end, the FDA estimates that toxic effects such as seizures can occur with rapid intake of about 1,200 mg of caffeine, which is less than half a teaspoon of pure caffeine [5].

Timing: caffeine and sleep on top of a morning stimulant

One randomized study gave 400 mg of caffeine at 0, 3 or 6 hours before habitual bedtime and found significant sleep disturbance versus placebo at every interval (P<0.05), using self-report plus a portable sleep monitor. The authors concluded that substantial caffeine should be avoided for at least 6 hours before bed [2].

What makes caffeine itself last longer

These factors change the caffeine side of the pair rather than the amphetamine side:

• Combined oral contraceptives: caffeine half-life 7.88 vs 5.37 hours and clearance 1.05 vs 1.75 mL/min/kg versus matched controls in one study [10]; a second study found half-life 10.7 vs 6.2 hours [12].
• Oral estradiol in 12 postmenopausal women: the paraxanthine-to-caffeine ratio fell by a mean of 29.2 after 8 weeks, consistent with CYP1A2 inhibition [13].
• Fluvoxamine: total caffeine clearance fell from 107 to 21 mL/min and half-life rose from 5 to 31 hours in 8 volunteers [9]; a second study found clearance 105 to 9.1 mL/min and half-life 4.9 to 56 hours in 7 volunteers, with no change in measured alertness, psychomotor performance or EEG effects after a single caffeine dose [14].
• Ciprofloxacin: the Cipro label describes itself as a CYP1A2 inhibitor and lists caffeine and xanthine derivatives as having reduced clearance, higher levels and a longer half-life, with monitoring for xanthine toxicity [15].
• Stopping smoking: caffeine clearance fell 36.1%, from 2.47 to 1.53 mL/min/kg, after heavy smokers quit [16].
• Pregnancy: mean half-life 8.3 hours in 57 pregnant women versus 3.4 hours in 25 men and non-pregnant women [4].