bioavailability
13 interactions related to bioavailability
atenolol + calcium
Calcium supplements and calcium-based antacids taken at the same time as atenolol bind it in the gut and reduce how much of the drug is absorbed, blunting its blood-pressure and heart-rate effects. Separating the two doses by several hours preserves atenolol's effect. Calcium from ordinary meals is generally not a concern.
alendronate + coffee
Coffee (and orange juice) sharply reduce the absorption of alendronate, an oral bisphosphonate whose baseline absorption is already very low. Taking the tablet with coffee instead of plain water can cut the absorbed amount enough to make the dose ineffective for protecting bone.
itraconazole + grapefruit
Grapefruit juice can reduce the absorption of itraconazole capsules in healthy-volunteer studies, lowering antifungal blood levels. The likely mechanism is a rise in gastric pH that interferes with the capsule's dissolution, which outweighs grapefruit's usual CYP3A4-inhibiting effect.
curcumin + fat
Curcumin is a lipophilic molecule with very low water solubility, and dietary fat improves its dissolution and incorporation into bile-acid micelles for intestinal absorption. Taking curcumin or turmeric with a fat-containing meal, and using lipid-based formulations, raises its plasma exposure compared with intake on an empty stomach.
turmeric + black pepper
Piperine, the active alkaloid in black pepper, slows the gut and liver enzymes that normally inactivate curcumin (the main bioactive in turmeric). Taking the two together substantially increases how much curcumin reaches the bloodstream, which is why piperine is one of the most common absorption enhancers in turmeric supplements. The same enzyme effect can also raise levels of some prescription drugs, so concentrated daily supplement doses warrant a pharmacist check for people on chronic medications.
lycopene + fat
Lycopene is a fat-soluble carotenoid whose absorption depends on incorporation into bile-acid micelles, which require dietary fat. Human studies show that eating lycopene-rich foods with a fat source — such as olive oil or avocado — substantially increases how much lycopene reaches the bloodstream.
gabapentin + antacids
Aluminum- and magnesium-containing antacids reduce the amount of gabapentin absorbed when the two are taken at the same time. The effect is mechanical (the antacid interferes with gabapentin's intestinal uptake) rather than acid- or pH-related, so it can be largely avoided by spacing the two doses a couple of hours apart and taking gabapentin after the antacid.
ginkgo + phosphatidylserine
Pairing a standardized ginkgo biloba extract with phosphatidylserine appears to improve absorption of ginkgo's active fraction. In one small placebo-controlled crossover trial, the ginkgo-phosphatidylserine complex produced modest improvements in memory performance and speed in healthy young adults, where the same dose of ginkgo alone did not.
magnesium + glycine
Magnesium and glycine are commonly combined as magnesium bisglycinate, a chelate whose clearest benefit is being gentle on the gut and improving adherence, rather than dramatically higher absorption.
curcumin + quercetin
In laboratory intestinal-cell models, quercetin slows the gut and liver enzymes (UDP-glucuronosyltransferase and CYP3A4) that normally break curcumin down quickly, which raised curcumin's measured permeability across the cell layer. Both polyphenols also act on overlapping anti-inflammatory and antioxidant pathways. The evidence is mechanistic and limited to in vitro work — no human trials have confirmed a real-world bioavailability or anti-inflammatory benefit from combining them.
whey protein + iron
Whey protein is usually consumed alongside calcium-rich milk minerals, and calcium competes with iron for absorption in the gut. When taken at the same time, a whey-plus-iron serving can modestly lower how much iron you absorb. The effect is largely driven by calcium, is generally modest, and is easily offset by taking a vitamin C source with your iron.
black pepper + propranolol
Piperine, the active alkaloid in black pepper, can inhibit intestinal P-glycoprotein and several liver enzymes that normally limit how much propranolol reaches the bloodstream. A small human study found that concentrated piperine raised propranolol's blood levels, so a stable dose may behave like a somewhat higher one, slightly amplifying its blood-pressure and heart-rate effects. Culinary pepper is not the concern; concentrated piperine supplements are.
quercetin + bromelain
Quercetin and bromelain are commonly co-formulated for inflammation and allergy support, and bromelain has its own anti-inflammatory action, but the popular claim that bromelain boosts quercetin absorption 2-3x is a vendor figure not backed by any human pharmacokinetic study.