Fosamax/Fosamax Plus Drug Interactions

Overview: Animal studies have demonstrated that FOSAMAX/FOSAMAX PLUS is highly concentrated in bone and is retained only minimally in soft tissue. No metabolites have been detected. Although alendronate is bound approximately 78% to plasma protein in humans, its plasma concentration is so low after oral dosing that only a small fraction of plasma-binding sites is occupied, resulting in a minimal potential for interference with the binding of other drugs. Alendronate is not excreted through the acidic or basic transport systems of the kidney in rats, and thus it is not anticipated to interfere with the excretion of other drugs by those systems in humans. In summary, FOSAMAX/FOSAMAX PLUS is not expected to interact with other drugs based on effects on protein binding, renal excretion, or metabolism of other drugs.
Drug-Drug Interactions: Alendronate Sodium: If taken at the same time it is likely that calcium supplements, antacids, other multivalent cations and other oral medications will interfere with absorption of FOSAMAX/FOSAMAX PLUS. Therefore, patients must wait at least one-half hour after taking FOSAMAX/FOSAMAX PLUS before taking any other oral medication.
Intravenous ranitidine was shown to double the bioavailability of oral alendronate. The clinical significance of this increased bioavailability and whether similar increases will occur in patients given oral H₂-antagonists is unknown; no other specific drug interaction studies were performed.
Concomitant use of hormone replacement therapy (HRT [estrogen ± progestin]) and FOSAMAX/FOSAMAX PLUS was assessed in two clinical studies of one or two years' duration in postmenopausal osteoporotic women. Combined use of FOSAMAX and HRT resulted in greater increases in bone mass, together with greater decreases in bone turnover, than seen with either treatment alone. In these studies, the safety and tolerability profile of the combination was consistent with those of the individual treatments (see Adverse Reactions: Clinical Trial Adverse Drug Reactions, Concomitant Use with Estrogen/Hormone Replacement Therapy).
The studies were too small to detect antifracture efficacy, and no significant differences in fracture incidence among the treatment groups were found.
Specific interaction studies were not performed. FOSAMAX/FOSAMAX PLUS was used in osteoporosis studies in men, postmenopausal women, and glucocorticoid users, with a wide range of commonly prescribed drugs without evidence of clinical adverse interactions.
In clinical studies, the incidence of upper gastrointestinal adverse events was increased in patients receiving daily therapy with dosages of FOSAMAX greater than 10 mg and ASA-containing products. This was not observed in a study with FOSAMAX 70 mg once weekly.
FOSAMAX/FOSAMAX PLUS may be administered to patients taking nonsteroidal anti-inflammatory drugs (NSAIDs). In a three-year, controlled, clinical study (n=2027) during which a majority of patients received concomitant NSAIDs, the incidence of upper gastrointestinal adverse events was similar in patients taking FOSAMAX 5 or 10 mg/day compared to those taking placebo.
However, since NSAID use is associated with gastrointestinal irritation, caution should be used during concomitant use with FOSAMAX/FOSAMAX PLUS.
Colecalciferol: Fosamax Plus: Drugs That May Impair the Absorption of Colecalciferol: Olestra, mineral oils, orlistat, and bile acid sequestrants (e.g. cholestyramine, colestipol) may impair the absorption of vitamin D.
Drugs That May Increase the Catabolism of Colecalciferol: Anticonvulsants, cimetidine, and thiazides may increase the catabolism of vitamin D.
Drug-Food Interactions: Food and beverages other than plain water may markedly reduce the absorption and effectiveness of alendronate. FOSAMAX/FOSAMAX PLUS must be taken at least one-half hour before the first food, beverage, or medication of the day with plain water only (see DOSAGE & ADMINISTRATION).
Drug-Herb Interactions: Herbal products may interfere with the absorption of alendronate. FOSAMAX/FOSAMAX PLUS must be taken at least one-half hour before any herbal products.
Drug-Laboratory Interactions: Interactions with laboratory tests have not been established.
Drug-Lifestyle Interactions: No studies on the effects on the ability to drive and use machines have been performed. However, certain adverse reactions that have been reported with FOSAMAX/FOSAMAX PLUS (e.g., dizziness, vertigo, visual disturbances, and severe bone, muscle or joint pain) may affect some patients' ability to drive or operate machinery. Individual responses to FOSAMAX/FOSAMAX PLUS may vary.