caffeine
29 interactions related to caffeine
caffeine + ashwagandha
Caffeine is a stimulant that raises alertness and cortisol; ashwagandha is an adaptogenic herb that, taken on its own, modestly lowers cortisol and perceived stress in human trials. People combine them hoping ashwagandha will take the edge off caffeine's jitters. That pairing is plausible but has not been tested directly in humans, so the 'calm focus' benefit remains theoretical rather than proven. The combination is generally well tolerated in healthy adults.
l-theanine + caffeine
L-theanine, an amino acid from tea, appears to smooth out caffeine's stimulant effects by promoting alpha-wave brain activity associated with relaxed alertness, while caffeine blocks adenosine receptors to increase arousal. Human trials and a meta-analysis suggest the combination can improve sustained attention and reaction time more than either alone, with fewer of caffeine's jittery side effects.
caffeine + theophylline
Caffeine and theophylline are closely related methylxanthines that share the CYP1A2 metabolic pathway and act on the same adenosine receptors. Taking them together can slow theophylline clearance and add to its stimulant and cardiovascular effects, which matters because theophylline has a very narrow safety margin.
lithium + caffeine
Caffeine increases the kidneys' clearance of lithium, so a steady caffeine habit is effectively built into your lithium dose. The risk is sudden change: stopping caffeine abruptly can push lithium levels up toward the toxic range, while sharply increasing caffeine can lower levels and let mood symptoms return.
caffeine + propranolol
Caffeine is a stimulant that nudges heart rate and blood pressure upward, partially opposing the direction propranolol works in. The effect is usually modest, but heavy or concentrated caffeine can blunt propranolol's benefit and worsen the tremor or anxiety it is often prescribed to control.
caffeine + ciprofloxacin
Ciprofloxacin inhibits the liver enzyme CYP1A2, which is the main pathway that clears caffeine. As a result, caffeine is broken down more slowly, its blood levels stay higher for longer, and its stimulant effects are amplified and prolonged while you are on the antibiotic.
caffeine + sertraline
Caffeine and sertraline do not share a receptor, but their side-effect profiles overlap. Both can cause anxiety, jitteriness, insomnia, stomach upset and headache, so these symptoms can stack — most noticeably during the first few weeks of sertraline treatment. Unlike fluvoxamine, sertraline does not meaningfully slow caffeine clearance.
caffeine + tyrosine
L-tyrosine is a precursor to the catecholamine neurotransmitters (dopamine, norepinephrine), and caffeine indirectly amplifies catecholamine signaling by blocking adenosine receptors. The pairing is popular as a focus stack, but the direct evidence is limited: tyrosine alone helps preserve cognition under stress or sleep loss, and caffeine aids alertness, yet no human trial has tested caffeine plus tyrosine on their own. The combination is generally well tolerated in healthy adults, with the main cautions involving MAO inhibitors, levodopa, and thyroid medication.
smoking + caffeine
Polycyclic aromatic hydrocarbons in tobacco smoke induce CYP1A2, the main liver enzyme that breaks down caffeine, so smokers clear caffeine faster and feel it less. When you quit smoking, that fast clearance fades within a few days and your usual caffeine can build up, contributing to jitters, anxiety, palpitations, and poor sleep that can be mistaken for nicotine withdrawal.
energy drinks + beta-blockers
Energy drinks and beta-blockers exert opposing cardiovascular effects: beta-blockers slow heart rate and lower blood pressure, while the caffeine and stimulant load in energy drinks pushes the sympathetic system the other way. This can blunt the medication's effect and, in susceptible people, help provoke an arrhythmia.
energy drinks + adderall
Energy drinks deliver caffeine alongside other stimulant ingredients such as taurine and guarana, producing additive sympathomimetic effects on top of the amphetamine salts in Adderall. Both raise heart rate, blood pressure, and adrenergic activity, which can bring on palpitations, elevated blood pressure, anxiety, and insomnia, and in rare cases more serious heart rhythm disturbances.
levothyroxine + coffee
Coffee can reduce how much levothyroxine you absorb when the two are taken at the same time. Chlorogenic acids and other compounds in coffee appear to bind the hormone in the gut, and coffee can also speed gastric transit, leaving less time for the tablet to dissolve. The effect largely disappears when the dose and the coffee are separated by enough time.
coffee + sertraline
Sertraline is a weak inhibitor of CYP1A2, the enzyme that clears caffeine, so it can slow caffeine metabolism mildly. More relevant in practice, caffeine can add to the jitteriness, palpitations, anxiety, and insomnia that often appear in the first weeks of sertraline. The pharmacokinetic effect is far smaller than with fluvoxamine and is usually minor.
chocolate + adenosine
Caffeine and theobromine from chocolate are competitive antagonists at A1 and A2A adenosine receptors. When intravenous adenosine or regadenoson is used for a cardiac stress test, or adenosine is used to terminate supraventricular tachycardia, recent methylxanthine intake can blunt the drug's effect and produce a falsely normal stress test or a failure to convert the arrhythmia.
chocolate + lithium
Chocolate contains caffeine, a mild diuretic that increases how much lithium the kidneys clear. Because lithium has a narrow therapeutic window, a large, sustained change in caffeine intake can nudge serum lithium levels — adding a steady caffeine habit can lower them, while abruptly stopping one can raise them. Chocolate is a relatively minor caffeine source compared with coffee or tea, so the effect matters most for heavy, consistent chocolate consumers who make a sudden change.
ginseng + caffeine
Ginseng and caffeine are both mild stimulants, so combining them can additively increase alertness, jitteriness, palpitations, or insomnia in sensitive people, though the best evidence shows no meaningful cardiac signal from ginseng itself.
caffeine + adderall
Caffeine and the amphetamine salts in Adderall are both sympathomimetic stimulants. Taking them together adds their effects, so heart rate, blood pressure, jitteriness and trouble sleeping tend to be more pronounced than with either alone.
caffeine + yohimbine
Caffeine and yohimbine are both stimulants that activate the sympathetic ('fight or flight') nervous system through different routes. Caffeine blocks adenosine receptors and raises catecholamine output; yohimbine blocks alpha-2 adrenergic receptors, increasing norepinephrine release. Taken together they add to each other's effects on heart rate, blood pressure, and anxiety. Yohimbine-containing products have been linked to emergency-department visits and hospitalizations for fast heart rate, high blood pressure, and severe anxiety.
caffeine + creatine
Daily high-dose caffeine taken throughout a creatine loading week may modestly blunt creatine's strength benefit, but ordinary pre-workout caffeine in someone already taking creatine daily is at worst neutral and often additive. There is no safety concern at normal intakes.
energy drinks + stimulants
Energy drinks layer caffeine, taurine, and guarana on top of any prescription or recreational stimulant (amphetamine, methylphenidate, modafinil, pseudoephedrine, cocaine), pushing heart rate, blood pressure, and central nervous system arousal in the same direction. Because the effects work along overlapping pathways, the combination can produce more strain than either source alone, raising the risk of palpitations, blood-pressure spikes, severe insomnia, and anxiety.
caffeine + clozapine
Caffeine and clozapine are both broken down by the liver enzyme CYP1A2, and caffeine competitively inhibits it. Large changes in caffeine intake - especially starting or stacking energy drinks - can raise clozapine to toxic levels, with a documented case report of severe toxicity and multiorgan failure.
coffee + propranolol
Caffeine in coffee acutely raises heart rate and blood pressure, which can partly counteract the heart-rate and blood-pressure-lowering effects of propranolol, a non-selective beta-blocker. Propranolol does not fully block this caffeine pressor response. Older claims that propranolol slows caffeine clearance appear to be wrong: a human study found propranolol slightly speeds caffeine elimination rather than slowing it.
guarana + caffeine medications
Guarana seeds are an unusually concentrated source of caffeine, carrying several times the caffeine of coffee beans, and that caffeine adds directly to any caffeine-containing medication (such as Excedrin, Fioricet, Cafergot, Anacin, Esgic, NoDoz, or Vivarin). Because the caffeine is additive and easy to overlook, stacking guarana on top of these products can push total caffeine intake into a range linked to tachycardia, hypertension, jitteriness, GI upset, insomnia, and — in published case reports — serious cardiac arrhythmias.
caffeine + oral contraceptives
Ethinyl estradiol in combined oral contraceptives inhibits CYP1A2, the liver enzyme that clears caffeine. This slows caffeine's breakdown and prolongs its half-life, so the same cup of coffee can leave more caffeine circulating for longer and intensify jitteriness, insomnia and palpitations.
caffeine + vitamin d
Higher caffeine intake is weakly associated with lower vitamin D status. In cell studies caffeine reduces vitamin D receptor (VDR) expression in bone-forming cells, and a large NHANES cross-sectional analysis links higher caffeine intake to a modestly greater chance of low serum 25-hydroxyvitamin D. The effect is small and matters most for people who already have low vitamin D, low calcium intake, and high bone-loss risk (for example, postmenopausal women). It is not an absorption-level interaction, so there is no need to separate the timing of a vitamin D supplement from coffee.
energy drinks + lithium
The caffeine in energy drinks increases how fast the kidneys clear lithium, so swings in caffeine intake can shift serum lithium in either direction. Heavy or rising caffeine intake can pull lithium toward the lower, less effective end of its narrow range, while abruptly cutting or stopping caffeine while on a stable lithium dose can push serum lithium up into the toxic range. Because lithium has one of the narrowest therapeutic windows in psychiatry, the variability of energy drink use is the real hazard.
coffee + ciprofloxacin
Ciprofloxacin inhibits CYP1A2, the liver enzyme that clears caffeine, slowing caffeine metabolism so a normal amount of coffee produces higher, longer-lasting caffeine levels and stronger stimulant effects.
coffee + antidepressants
Some antidepressants slow how fast the body clears caffeine by inhibiting the liver enzyme CYP1A2 — fluvoxamine does this most strongly, while fluoxetine, sertraline, paroxetine, and duloxetine have milder effects. At the same time, caffeine independently worsens anxiety, insomnia, tremor, and a racing heart, the very symptoms antidepressants are often prescribed to relieve. With MAOIs, very high caffeine intake has been linked in case reports to blood pressure spikes.
hot chocolate + sleep medications
Hot chocolate contains caffeine and theobromine, methylxanthines that block adenosine receptors and mildly promote wakefulness. Because sleep medications such as zolpidem, eszopiclone, and benzodiazepines work by dampening wakefulness, an evening cup can work in the opposite direction. The amount of caffeine in hot chocolate is small, so the practical effect for most people is minor, but timing it well away from bedtime is a simple, sensible habit.