The following adverse reactions have been reported during post-approval use of zoledronic acid. Because these reports are from a population of uncertain size and are subject to confounding factors, it is not possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Osteonecrosis of the Jaw
Cases of osteonecrosis (primarily involving the jaws) have been reported predominantly in cancer patients treated with intravenous bisphosphonates including zoledronic acid. Many of these patients were also receiving chemotherapy and corticosteroids which may be a risk factor for ONJ. Data suggests a greater frequency of reports of ONJ in certain cancers, such as advanced breast cancer and multiple myeloma. The majority of the reported cases are in cancer patients following invasive dental procedures, such as tooth extraction. It is therefore prudent to avoid invasive dental procedures as recovery may be prolonged [see Warnings And Precautions (5)].
Acute Phase Reaction
Within three days after zoledronic acid administration, an acute phase reaction has been reported, with symptoms including pyrexia, fatigue, bone pain and/or arthralgias, myalgias, chills, and influenza-like illness; these symptoms usually resolve within three days of onset, but resolution could take up to 7 to 14 days. However, some of these symptoms have been reported to persist for a longer duration.
Severe and occasionally incapacitating bone, joint, and/or muscle pain has been reported with bisphosphonate use [see Warnings And Precautions (5)].
Atypical Subtrochanteric and Diaphyseal Femoral Fractures
Atypical subtrochanteric and diaphyseal femoral fractures have been reported with bisphosphonate therapy, including zoledronic acid [see Warnings and Precautions (5.6)].
Ocular Adverse Events
Cases of uveitis, scleritis, episcleritis, conjunctivitis, iritis, and orbital inflammation including orbital edema have been reported during post-marketing use. In some cases, symptoms resolved with topical steroids.
There have been rare reports of allergic reaction with intravenous zoledronic acid including angioedema and bronchoconstriction. Very rare cases of anaphylactic reaction/shock have also been reported.
Additional adverse reactions reported in post-marketing use include:
CNS : taste disturbance, hyperesthesia, tremor; Special Senses : blurred vision; Gastrointestinal : dry mouth; Skin : Increased sweating; Musculoskeletal : muscle cramps; Cardiovascular : hypertension, bradycardia, hypotension (associated with syncope or circulatory collapse primarily in patients with underlying risk factors); Respiratory: bronchospasms, interstitial lung disease (ILD) with positive re-challenge; Renal : hematuria, proteinuria; General Disorders and Administration Site : weight increase, influenza-like illness (pyrexia, asthenia, fatigue or malaise) persisting for greater than 30 days; Laboratory Abnormalities : hyperkalemia, hypernatremia.
In vitro studies that the plasma protein binding of zoledronic acid is low, with the unbound fraction ranging from 60-77%. In vitro studies also indicate that zoledronic acid does not inhibit microsomal CYP450 enzymes. In vivo studies showed that zoledronic acid is not metabolized, and is excreted into the urine as the intact drug.
Caution is advised when bisphosphonates are administered with aminoglycosides, since these agents may have an additive effect to lower serum calcium level for prolonged periods. This effect has not been reported in zoledronic acid clinical trials.
Caution should also be exercised when zoledronic acid is used in combination with loop diuretics due to an increased risk of hypocalcemia.
Caution is indicated when zoledronic acid is used with other potentially nephrotoxic drugs.
No dose adjustment for zoledronic acid 4 mg is needed when co-administered with thalidomide. In a pharmacokinetic study of 24 patients with multiple myeloma, zoledronic acid 4 mg given as a 15 minute infusion was administered either alone or with thalidomide (100 mg once daily on days 1 to 14 and 200 mg once daily on days 15 to 28). Co‑administration of thalidomide with zoledronic acid did not significantly change the pharmacokinetics of zoledronic acid or creatinine clearance.
Pregnancy Category D [see Warnings and Precaution (5.9)]
There are no adequate and well-controlled studies of zoledronic acid in pregnant women. Zoledronic acid may cause fetal harm when administered to a pregnant woman. Bisphosphonates, such as zoledronic acid, are incorporated into the bone matrix and are gradually released over periods of weeks to years. The extent of bisphosphonate incorporation into adult bone, and hence, the amount available for release back into the systemic circulation, is directly related to the total dose and duration of bisphosphonate use. Although there are no data on fetal risk in humans, bisphosphonates do cause fetal harm in animals, and animal data suggest that uptake of bisphosphonates into fetal bone is greater than into maternal bone. Therefore, there is a theoretical risk of fetal harm (e.g., skeletal and other abnormalities) if a woman becomes pregnant after completing a course of bisphosphonate therapy. The impact of variables such as time between cessation of bisphosphonate therapy to conception, the particular bisphosphonate used, and the route of administration (intravenous versus oral) on this risk has not been established. If this drug is used during pregnancy or if the patient becomes pregnant while taking or after taking this drug, the patient should be apprised of the potential hazard to the fetus.
In female rats given subcutaneous doses of zoledronic acid of 0.01, 0.03, or 0.1 mg/kg/day beginning 15 days before mating and continuing through gestation, the number of stillbirths was increased and survival of neonates was decreased in the mid- and high-dose groups (≥ 0.2 times the human systemic exposure following an intravenous dose of 4 mg, based on an AUC comparison). Adverse maternal effects were observed in all dose groups (with a systemic exposure of ≥ 0.07 times the human systemic exposure following an intravenous dose of 4 mg, based on an AUC comparison) and included dystocia and periparturient mortality in pregnant rats allowed to deliver. Maternal mortality may have been related to drug-induced inhibition of skeletal calcium mobilization, resulting in periparturient hypocalcemia. This appears to be a bisphosphonate-class effect.
In pregnant rats given a subcutaneous dose of zoledronic acid of 0.1, 0.2, or 0.4 mg/kg/day during gestation, adverse fetal effects were observed in the mid- and high-dose groups (with systemic exposures of 2.4 and 4.8 times, respectively, the human systemic exposure following an intravenous dose of 4 mg, based on an AUC comparison). These adverse effects included increases in pre- and post-implantation losses, decreases in viable fetuses, and fetal skeletal, visceral, and external malformations. Fetal skeletal effects observed in the high-dose group included unossified or incompletely ossified bones, thickened, curved or shortened bones, wavy ribs, and shortened jaw. Other adverse fetal effects observed in the high-dose group included reduced lens, rudimentary cerebellum, reduction or absence of liver lobes, reduction of lung lobes, vessel dilation, cleft palate, and edema. Skeletal variations were also observed in the low-dose group (with systemic exposure of 1.2 times the human systemic exposure following an intravenous dose of 4 mg, based on an AUC comparison). Signs of maternal toxicity were observed in the high-dose group and included reduced body weights and food consumption, indicating that maximal exposure levels were achieved in this study.
In pregnant rabbits given subcutaneous doses of zoledronic acid of 0.01, 0.03, or 0.1 mg/kg/day during gestation (≤0.5 times the human intravenous dose of 4 mg, based on a comparison of relative body surface areas), no adverse fetal effects were observed. Maternal mortality and abortion occurred in all treatment groups (at doses ≥0.05 times the human intravenous dose of 4 mg, based on a comparison of relative body surface areas). Adverse maternal effects were associated with, and may have been caused by, drug-induced hypocalcemia.
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