CABERGOLINE — cabergoline tablet
Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc.
Cabergoline Tablets, USP contain Cabergoline USP, a dopamine receptor agonist. The chemical name for Cabergoline USP is 1-[(6-allylergolin-8ß-yl)-carbonyl]-1-[3-(di- methylamino)propyl]-3-ethylurea. Its molecular formula is C26 H37 N5 O2 , and its molecular weight is 451.62. The structural formula is as follows:
Cabergoline USP is a white powder soluble in ethyl alcohol, chloroform, and N, N-dimethylformamide (DMF); slightly soluble in 0.1N hydrochloric acid; very slightly soluble in n-hexane; and insoluble in water.
Each tablet, for oral administration, contains 0.5 mg of Cabergoline USP. Inactive ingredients consist of citric acid, croscarmellose sodium, magnesium stearate and microcrystalline cellulose.
Mechanism of Action: The secretion of prolactin by the anterior pituitary is mainly under hypothalamic inhibitory control, likely exerted through release of dopamine by tuberoinfundibular neurons. Cabergoline is a long-acting dopamine receptor agonist with a high affinity for D2 receptors. Results of in vitro studies demonstrate that cabergoline exerts a direct inhibitory effect on the secretion of prolactin by rat pituitary lactotrophs. Cabergoline decreased serum prolactin levels in reserpinized rats. Receptor-binding studies indicate that cabergoline has low affinity for dopamine D1 , a1 — and a2 -adrenergic, and 5-HT1 — and 5-HT2 -serotonin receptors.
Clinical Studies: The prolactin-lowering efficacy of cabergoline was demonstrated in hyperprolactinemic women in two randomized, double-blind, comparative studies, one with placebo and the other with bromocriptine. In the placebo-controlled study (placebo n=20; cabergoline n=168), cabergoline produced a dose-related decrease in serum prolactin levels with prolactin normalized after 4 weeks of treatment in 29%, 76%, 74% and 95% of the patients receiving 0.125, 0.5, 0.75, and 1 mg twice weekly, respectively.
In the 8-week, double-blind period of the comparative trial with bromocriptine (cabergoline n=223; bromocriptine n=236 in the intent-to-treat analysis), prolactin was normalized in 77% of the patients treated with cabergoline at 0.5 mg twice weekly compared with 59% of those treated with bromocriptine at 2.5 mg twice daily. Restoration of menses occurred in 77% of the women treated with cabergoline, compared with 70% of those treated with bromocriptine. Among patients with galactorrhea, this symptom disappeared in 73% of those treated with cabergoline compared with 56% of those treated with bromocriptine.
Absorption: Following single oral doses of 0.5 mg to 1.5 mg given to 12 healthy adult volunteers, mean peak plasma levels of 30 to 70 picograms (pg)/mL of cabergoline were observed within 2 to 3 hours. Over the 0.5 to 7 mg dose range, cabergoline plasma levels appeared to be dose-proportional in 12 healthy adult volunteers and nine adult parkinsonian patients. A repeat-dose study in 12 healthy volunteers suggests that steady-state levels following a once-weekly dosing schedule are expected to be twofold to threefold higher than after a single dose. The absolute bioavailability of cabergoline is unknown. A significant fraction of the administered dose undergoes a first-pass effect. The elimination half-life of cabergoline estimated from urinary data of 12 healthy subjects ranged between 63 to 69 hours. The prolonged prolactin-lowering effect of cabergoline may be related to its slow elimination and long half-life.
Distribution: In animals, based on total radioactivity, cabergoline (and/or its metabolites) has shown extensive tissue distribution. Radioactivity in the pituitary exceeded that in plasma by >100-fold and was eliminated with a half-life of approximately 60 hours. This finding is consistent with the long-lasting prolactin-lowering effect of the drug. Whole body autoradiography studies in pregnant rats showed no fetal uptake but high levels in the uterine wall. Significant radioactivity (parent plus metabolites) detected in the milk of lactating rats suggests a potential for exposure to nursing infants. The drug is extensively distributed throughout the body. Cabergoline is moderately bound (40% to 42%) to human plasma proteins in a concentration-independent manner. Concomitant dosing of highly protein-bound drugs is unlikely to affect its disposition.
Metabolism: In both animals and humans, cabergoline is extensively metabolized, predominately via hydrolysis of the acylurea bond or the urea moiety. Cytochrome P-450 mediated metabolism appears to be minimal. Cabergoline does not cause enzyme induction and/or inhibition in the rat. Hydrolysis of the acylurea or urea moiety abolishes the prolactin-lowering effect of cabergoline, and major metabolites identified thus far do not contribute to the therapeutic effect.
Excretion: After oral dosing of radioactive cabergoline to five healthy volunteers, approximately 22% and 60% of the dose was excreted within 20 days in the urine and feces, respectively. Less than 4% of the dose was excreted unchanged in the urine. Nonrenal and renal clearances for cabergoline are about 3.2 L/min and 0.08 L/min, respectively. Urinary excretion in hyperprolactinemic patients was similar.
Renal Insufficiency: The pharmacokinetics of cabergoline were not altered in 12 patients with moderate-to severe renal insufficiency as assessed by creatinine clearance.
Hepatic Insufficiency: In 12 patients with mild-to-moderate hepatic dysfunction (Child-Pugh score ≤10), no effect on mean cabergoline Cmax or area under the plasma concentration curve (AUC) was observed. However, patients with severe insufficiency (Child-Pugh score >10) show a substantial increase in the mean cabergoline Cmax and AUC, and thus necessitate caution.
Elderly: Effect of age on the pharmacokinetics of cabergoline has not been studied.
In 12 healthy adult volunteers, food did not alter cabergoline kinetics.
Dose response with inhibition of plasma prolactin, onset of maximal effect, and duration of effect has been documented following single cabergoline doses to healthy volunteers (0.05 to 1.5 mg) and hyperprolactinemic patients (0.3 to 1 mg). In volunteers, prolactin inhibition was evident at doses >0.2 mg, while doses ≥ 0.5 mg caused maximal suppression in most subjects. Higher doses produce prolactin suppression in a greater proportion of subjects and with an earlier onset and longer duration of action. In 12 healthy volunteers, 0.5, 1 and 1.5 mg doses resulted in complete prolactin inhibition, with a maximum effect within 3 hours in 92% to 100% of subjects after the 1 and 1.5 mg doses compared with 50% of subjects after the 0.5 mg dose.
In hyperprolactinemic patients (n=51), the maximal prolactin decrease after a 0.6 mg single dose of cabergoline was comparable to 2.5 mg bromocriptine; however, the duration of effect was markedly longer (14 days vs. 24 hours). The time to maximal effect was shorter for bromocriptine than cabergoline (6 hours vs. 48 hours).
In 72 healthy volunteers, single or multiple doses (up to 2 mg) of cabergoline resulted in selective inhibition of prolactin with no apparent effect on other anterior pituitary hormones (GH, FSH, LH, ACTH, and TSH) or cortisol.
INDICATIONS AND USAGE
Cabergoline Tablets, USP are indicated for the treatment of hyperprolactinemic disorders, either idiopathic or due to pituitary adenomas
Cabergoline Tablets, USP are contraindicated in patients with
- Uncontrolled hypertension or known hypersensitivity to ergot derivatives.
- History of cardiac valvular disorders, as suggested by anatomical evidence of valvulopathy of any valve, determined by pre-treatment evaluation including echocardiographic demonstration of valve leaflet thickening, valve restriction, or mixed valve restriction-stenosis (See WARNINGS).
- History of pulmonary, pericardial, or retroperitoneal fibrotic disorders (See WARNINGS).
1. Pregnancy: Dopamine agonists in general should not be used in patients with pregnancy-induced hypertension, for example, preeclampsia, eclampsia, and postpartum hypertension, unless the potential benefit is judged to outweigh the possible risk.
2. Fibrotic Complications:
a. Cardiac Valvulopathy:
All patients should undergo a cardiovascular evaluation, including echocardiogram to assess the potential presence of valvular disease. If valvular disease is detected, the patient should not be treated with Cabergoline (See CONTRAINDICATIONS). Post-marketing cases of cardiac valvulopathy have been reported in patients receiving Cabergoline. These cases have generally occurred during administration of high doses of Cabergoline (>2mg/day) used for the treatment of Parkinson’s disease. Cases of cardiac valvulopathy have also been reported in patients receiving lower doses for the treatment of hyperprolactinemic disorders.
A multi-country, retrospective cohort study using general practice records and record linkage systems in the UK, Italy and the Netherlands was conducted to assess the association between new use of dopamine agonists including cabergoline (n=27,812) for Parkinson’s disease and hyperprolactinemia and cardiac valvular regurgitation (CVR), other fibroses, and other cardiopulmonary events over a maximum of 12 years of follow up. In this study, the use of cabergoline among persons with Parkinson’s disease was associated with an increased risk of CVR when compared to non-ergot-derived dopamine agonists (DAs) and levodopa [Incidence Rate (IR) per 10,000 person years of 68.1 (95% confidence interval (CI): 37.2 to 115.3) for cabergoline vs. 10.0 (95% CI: 5.2 to 19.4) for non-ergot DAs and 11.3 (95% CI: 7.2 to 17.0) for levodopa]. In the study analysis confined to persons with dopamine agonist-treated hyperprolactinemia (n=8,386), when compared to non-use (n=15,147), persons exposed to cabergoline did not have an elevated risk of CVR. The findings with respect to the risk of CVR associated with cabergoline treatment for persons with Parkinson’s disease (increased risk) and those with hyperprolactinemia (no increased risk) are consistent with the findings in other published studies.
Physicians should use the lowest effective dose of Cabergoline for the treatment of hyperprolactinemic disorders and should periodically reassess the need for continuing therapy with Cabergoline. Following treatment initiation, clinical and diagnostic monitoring (for example, chest x-ray, CT scan and cardiac echocardiogram) should be conducted to assess the risk of cardiac valvulopathy. The recommended frequency of routine echocardiographic monitoring is every 6 to 12 months or as clinically indicated with the presence of signs and symptoms such as edema, new cardiac murmur, dyspnea or congestive heart failure.
Cabergoline should be discontinued if an echocardiogram reveals new valvular regurgitation, valvular restriction or valve leaflet thickening.
Cabergoline should be used with caution in patients exposed to other medications associated with valvulopathy.
b. Extracardiac Fibrotic Reactions:
Post-marketing cases of pleural, pericardial and retroperitoneal fibrosis have been following administration of Cabergoline. Some reports were in patients previously treated with other ergotinic dopamine agonists. Cabergoline should not be used in patients with a history of cardiac or extracardiac fibrotic disorders.
Fibrotic disorders can have an insidious onset and patients should be monitored for manifestations of progressive fibrosis. Therefore, during treatment, attention should be paid to the signs and symptoms of:
- Pleuro-pulmonary disease such as dyspnea, shortness of breath, persistent cough or chest pain
- Renal insufficiency or ureteral/abdominal vascular obstruction that may occur with pain in the loin/flank and lower limb edema as well as any possible abdominal masses or tenderness that may indicate retroperitoneal fibrosis.
- Cardiac failure: Cases of valvular and pericardial fibrosis have ofter manifested as cardiac failure. Therefore, valvular fibrosis (and constrictive pericarditis) should be excluded if such symptoms occur.
Clinical and diagnostic monitoring such as erythrocyte sedimentation rate, chest x-ray, serum creatinine measurements, and other investigations should be considered at baseline and as necessary while patients are treated with Cabergoline.
Following diagnosis of pleural effusion or pulmonary fibrosis, the discontinuance of Cabergoline was reported to result in improvement of signs and symptoms.
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