bioavailability
13 interactions related to bioavailability
atenolol + calcium
Calcium salts taken together with atenolol form a complex in the gut that cuts atenolol's peak plasma level by roughly 51% and total exposure (AUC) by 32%, blunting its blood-pressure and heart-rate effects 12 hours later. The effect was first quantified in a 1981 pharmacokinetic study and is the main reason high-dose calcium and atenolol should be separated in time.
alendronate + coffee
Studies cited in the FDA label show coffee (and orange juice) reduce alendronate bioavailability by approximately 60%. Given the drug's already minuscule baseline absorption of ~0.6%, this drop can render the dose therapeutically ineffective.
itraconazole + grapefruit
Grapefruit juice has been shown in healthy-volunteer studies to reduce itraconazole capsule peak concentrations by roughly 35 percent and overall AUC by about 43 percent, likely through changes in gastric pH and intestinal effects that impair the capsule's absorption.
curcumin + fat
Curcumin is a lipophilic molecule with very low water solubility, and dietary fat dramatically improves its dissolution and incorporation into bile acid micelles for intestinal absorption. Lipidic formulations and meals containing fat increase curcumin's plasma exposure compared with intake on an empty stomach.
turmeric + black pepper
Piperine, the active alkaloid in black pepper, inhibits hepatic and intestinal glucuronidation of curcumin and other compounds, and a landmark human study reported a 2000% increase in curcumin bioavailability when 20 mg piperine was co-administered with 2 g curcumin. This is one of the most cited absorption-enhancement combinations in the supplement literature.
lycopene + fat
Lycopene is a fat-soluble carotenoid whose absorption depends on incorporation into bile acid micelles, which require dietary fat. A landmark study showed adding olive oil to tomatoes increased plasma trans-lycopene by 82%, and avocado co-consumption with tomato salsa increased lycopene AUC 4.4-fold.
gabapentin + antacids
Aluminum and magnesium-containing antacids reduce the bioavailability of gabapentin by approximately 20% when taken simultaneously, and magnesium oxide specifically can reduce gabapentin AUC by up to 43%. The mechanism is reduced intestinal absorption, not pH-related (proton pump inhibitors do not cause the same effect).
ginkgo + phosphatidylserine
Ginkgo biloba improves cerebral blood flow and has antioxidant effects; complexing it with phosphatidylserine substantially enhances absorption of its active terpene lactones and flavone glycosides. The Virtiva complex (ginkgo + phosphatidylserine) showed improved secondary memory and faster memory task performance versus ginkgo alone in a placebo-controlled crossover trial.
magnesium + glycine
When magnesium is bound (chelated) to two glycine molecules as magnesium bisglycinate, the amino-acid carrier protects the mineral from binding with phytates and oxalates in the gut and shuttles it across the intestinal wall more efficiently, producing higher bioavailability and less GI upset than inorganic salts like magnesium oxide. Glycine itself is also an inhibitory neurotransmitter that may lower core body temperature and shorten sleep latency, so the pairing supports relaxation as well as absorption.
curcumin + quercetin
Quercetin inhibits the same UDP-glucuronosyltransferase and CYP3A4 enzymes that rapidly metabolize curcumin, raising its plasma exposure, and both polyphenols share complementary anti-inflammatory and antioxidant pathways. In vitro intestinal models and animal studies show the combination increases apical-to-basal uptake of curcumin and amplifies NF-kB pathway suppression.
whey protein + iron
Whey protein contains calcium and bioactive peptides that can chelate iron in the gut and reduce its absorption. Studies in iron-fortified casein-whey drinks show calcium added with whey reduces iron absorption by approximately 18 to 27 percent.
black pepper + propranolol
Piperine, the active alkaloid in black pepper, inhibits CYP3A4, CYP2C9, and intestinal P-glycoprotein, increasing the oral bioavailability and serum concentration of propranolol and other beta-blockers, which can amplify blood pressure and heart rate reduction.
quercetin + bromelain
Bromelain is a proteolytic enzyme complex from pineapple that improves quercetin absorption (reportedly 2-3x) and adds independent anti-inflammatory effects (fibrinolytic activity, COX modulation, bradykinin reduction). The pair is commonly co-formulated for inflammation, allergy, and immune support.