Glerelin

Uses

For treatment of prostate cancer, endometriosis, uterine fibroids and premature puberty

Glerelin is also used to associated treatment for these conditions: Advanced Prostate Cancer, Anemia, Central Precocious Puberty (CPP), Endometriosis

How Glerelin works

Gonadotropin-releasing hormone (GnRH) is a naturally occurring decapeptide that modulates the hypothalamic-pituitary-gonadal (HPG) axis. GnRH binds to corresponding receptors (GnRHRs) on the anterior pituitary gonadotropes, which in turn release luteinizing hormone (LH) and follicle-stimulating hormone (FSH); these, in turn, affect the downstream synthesis and release of the sex hormones testosterone, dihydrotestosterone, estrone, and estradiol.

Despite the variety of conditions indicated for treatment with leuprolide, the mechanism of action underlying efficacy is the same in all cases. As a GnRHR agonist, leuprolide binds to and initially activates downstream LH and FSH release; this initial spike in gonadotropin levels is responsible for some of the adverse effects associated with treatment. After 2-4 weeks of treatment, continuous stimulation of GnRHR results in feedback inhibition and significant downregulation of LH, FSH, and their corresponding downstream effects, producing a therapeutic benefit. These effects are reversible upon treatment discontinuation.

Dosage

Glerelin dosage

Adult:Palliative treatment of advanced prostate cancer:1 mg as single daily dose by SC inj. Depot preparations may be given by IM or SC route, dosage and route may differ between different brands and countries. In the UK: As depot preparations: 3.75 mg every mth as single IM/SC inj; or 11.25 mg every 3 mth via SC inj. In the US: As depot preparations: 7.5 mg every mth, or 22.5 mg every 3 mth, or 30 mg every 4 mth via IM/SC inj depending on the preparations; or 45 mg every 6 mth via SC inj.

Endometriosis:As depot preparations: 3.75 mg every mth given as a single IM/SC inj or 11.25 mg every 3 mth as IM depot Inj. Initiate treatment during the 1st 5 days of menstrual cycle up to 6 mth. May be used with norethindrone acetate 5 mg daily for initial management of endometriosis and for management of recurrence symptoms. Duration of retreatment: Should not exceed one additional 6 mth course.

Uterine fibroids:As depot preparations: In combination with iron therapy for women with anaemia due to uterine fibroids, 3.75 mg every mth given as a single IM/SC inj or 11.25 mg every 3 mth as IM Inj. Treatment duration: Usually up to 3 mth.

Preparation for intrauterine surgery:Endometrial preparation prior to intrauterine surgery: As depot preparations: 3.75 mg as a single inj via IM/SC given 5-6 wk before the procedure; therapy should be initiated during days 3-5 of the menstrual cycle.

Child:Precocious puberty:As aqueous soln inj: Initial: 50 mcg/kg daily by SC inj, may be titrated upwards by 10 mcg/kg/day if total down-regulation is not achieved. As depot preparations: Initial: 0.3 mg/kg/dose (minimum dose: 7.5 mg) given every 4 wk via IM inj; which equates to children ≤25 kg: 7.5 mg; >25-37.5 kg: 11.25 mg and >37.5 kg: 15 mg given every 4 wk. Maintenance: May titrate dose upwards in steps of 3.75 mg every 4 wk if down-regulation is not achieved. Consider discontinuing therapy before age 11 (females) and age 12 (males).

Side Effects

Treatment of precocious puberty: General pain, headache, acne, rash, seborrhoea, emotional lability, vaginitis, vaginal bleeding vaginal discharge

Treatment of prostate cancer: Transient worsening of signs and symptoms (usually increase in bone pain), ECG changes, high blood pressure, peripheral oedema, anorexia, constipation, nausea, vomiting, anaemia, myalgia, dizziness, general pain, headache, insomnia or sleep disorder, sinus congestion, urinary frequency/urgency, haematuria, UTI, asthaenia, physiological effects of decreased testosterone (e.g. gynaecomastia, breast tenderness, decreased testicular size, hot flashes, impotence).

Treatment of endometriosis and uterine fibroids treatment: General pain, headache, asthaenia, nausea, vomiting, oedema, weight changes, acne, hirsutism, dizziness, insomnia, sleep disturbance, paraesthesias, skin reactions, effects of hypoestrogenism such as hot flashes, joint disorder, myalgia, decreased libido, depression, emotional lability, nervousness, breast tenderness, vaginitis.

Toxicity

Glerelin is considered extremely safe, with low dose-related toxicity and comparatively mild adverse effects. Prostate cancer patients treated with leuprolide at doses as high as 20 mg/day for two years showed no additional adverse effects compared to those receiving 1 mg/day.

Precaution

Vary inj site periodically. May cause transient elevation of testosterone levels during the first 1-2 wk, which may lead to worsening or onset of new symptoms (e.g. bone pain, neuropathy, haematuria) in prostate cancer patients. Ureteral obstruction and spinal cord compression have been reported; closely monitor patients with urinary obstruction and/or metastatic vertebral lesion. Leuprorelin is associated with increased risk of diabetes and certain CV diseases (heart attack, sudden cardiac death, stroke) when used in men for treatment of prostate cancer. For prostate cancer, monitor response by testosterone and prostate-specific antigen (PSA) levels. For precocious puberty in children, monitor response by GnRH stimulation test sex steroid levels 1-2 month after treatment initiation. Leuprorelin usually inhibits ovulation and stops menstruation in women, but does not incur contraception, non-hormonal contraception should be used as pregnancy is contraindicated. May cause adverse reactions associated with hypoestrogenism and loss in bone density.

Food Interaction

Glerelin Drug Interaction

Unknown: aspirin, aspirin, calcium / vitamin d, calcium / vitamin d, bicalutamide, bicalutamide, tamsulosin, tamsulosin, levothyroxine, levothyroxine, cyanocobalamin, cyanocobalamin, pyridoxine, pyridoxine, ascorbic acid, ascorbic acid, cholecalciferol, cholecalciferol, abiraterone, abiraterone

Glerelin Disease Interaction

Moderate: cardiovascular disease, diabetes, QT interval prolongation, bone mineral density, seizures

Volume of Distribution

Glerelin has an apparent steady-state volume of distribution of 27 L following intravenous bolus administration to healthy males. The volume of distribution for indicated routes of subcutaneous or intramuscular injection has not been reported.

Elimination Route

Glerelin is typically administered as a single-dose long-acting formulation employing either microsphere or biodegradable solid depot technologies. Regardless of the exact formulation and initial dose strength, the C_max is typically achieved by 4-5 hours post-injection and displays large variability in the range of 4.6 - 212 ng/mL. Eventual steady-state kinetics are typically achieved by four weeks, with a narrower range of 0.1 - 2 ng/mL. No studies on the effects of food on absorption have been carried out.

Half Life

Glerelin has a terminal elimination half-life of approximately three hours.

Clearance

Glerelin administered as a 1 mg intravenous bolus in healthy males has a mean systemic clearance between 7.6 and 8.3 L/h.

Elimination Route

Following administration of 3.75 mg leuprolide depot suspension to three patients, less than 5% of the initial dose was recovered as unchanged or pentapeptide metabolite in the urine.

Pregnancy & Breastfeeding use

Category X: Studies in animals or human beings have demonstrated foetal abnormalities or there is evidence of foetal risk based on human experience or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are or may become pregnant.

Contraindication

Pregnancy, lactation; hypersensitivity to GnRH, GnRH agonist analogs or product excipients; undiagnosed abnormal vaginal bleeding.

Innovators Monograph

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