cyp1a2
14 interactions related to cyp1a2
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.
propranolol + st. john's wort
St. John's Wort induces several liver drug-metabolizing enzymes, including CYP1A2 and CYP3A4, plus the transporter P-glycoprotein. Propranolol is cleared mainly through CYP1A2 and CYP2D6, so regular St. John's Wort use can plausibly speed up its breakdown and weaken its effect. Direct studies of this specific pair are lacking; the concern is based on St. John's Wort's confirmed enzyme-inducing action, its documented lowering of theophylline (which shares propranolol's CYP1A2 pathway), and a case report of lost intraocular-pressure control in a glaucoma patient on a topical beta-blocker.
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.
smoking + clozapine
Polycyclic aromatic hydrocarbons in tobacco smoke (not nicotine) strongly induce CYP1A2, the liver enzyme that handles most clozapine metabolism, so smokers tend to have lower clozapine levels and need higher doses. The greater danger is stopping smoking: levels can climb sharply over a few days as the enzyme returns to baseline, risking sedation, seizures, and toxicity unless the dose is reviewed.
smoking + olanzapine
Polycyclic aromatic hydrocarbons in cigarette smoke induce CYP1A2, the main enzyme that breaks down olanzapine, so smokers clear the drug faster and run lower blood levels. When someone quits, levels rise over the following days to weeks and side effects can emerge on a previously stable dose. The effect is driven by combustion products, not nicotine.
smoking + theophylline
Combustion products in tobacco smoke induce the liver enzyme CYP1A2, speeding up how fast the body clears theophylline. Smokers therefore tend to need more theophylline to stay in range, and stopping smoking can reverse this within days and push levels into a toxic range unless the dose is reviewed.
smoking + propranolol
Cigarette smoking induces hepatic metabolism of propranolol (mainly via CYP1A2 and glucuronidation), increasing its clearance and lowering propranolol blood levels in smokers compared with non-smokers. Nicotine also independently raises heart rate, blood pressure, and circulating catecholamines, partly counteracting propranolol's beta-blocking effect. Both effects reverse when a person quits smoking.
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.
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.
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.
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.
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.