Cinacalcet

Oral
Secondary hyperparathyroidism in patients with chronic kidney disease on dialysis
Adult: Alone or in combination with phosphate binders and/or vitamin D sterols: Initially, 30 mg once daily, may titrate dose in increments of 30 mg every 2-4 weeks to Max of 180 mg once daily, to achieve the target intact PTH (iPTH) levels of 150-300 pg/mL. Alternatively, 25 mg once daily, may be adjusted within range of 25-75 mg once daily; if there is no improvement in PTH levels, may increase by 25 mg increments at least every 3 weeks up to 100 mg once daily. Dosage requirements and preparation may vary among countries and individual products. Dose reduction, dosing interruption, or discontinuation may be required based on the PTH and serum Ca levels (refer to detailed product guideline). In patients switching from etelcalcetide: Discontinue etelcalcetide for at least 4 weeks before initiation of therapy or do not initiate cinacalcet until at least 3 subsequent haemodialysis sessions are completed, and ensure serum Ca levels are within the normal range prior to therapy.

Oral
Hypercalcaemia associated with parathyroid carcinoma
Adult: Initially, 30 mg bid, titrated every 2-4 weeks through sequential doses of 30 mg bid, 60 mg bid, 90 mg bid, and 90 mg 3 or 4 times daily as needed to normalise the serum Ca levels.

Oral
Hypercalcaemia associated with primary hyperparathyroidism
Adult: In patients who would be candidates for parathyroidectomy based on serum Ca levels, but are unable to undergo the surgery (clinically inappropriate or contraindicated): Initially, 30 mg bid, titrated every 2-4 weeks through sequential doses of 30 mg bid, 60 mg bid, 90 mg bid, and 90 mg 3 or 4 times daily as needed to normalise the serum Ca levels.

Special Populations: Patients who started or stopped smoking; patients who started or have discontinued concomitant therapy with strong CYP3A4 inhibitors (e.g. ketoconazole, itraconazole) or inducers (e.g. rifampicin): Dose adjustment may be needed.

Should be taken with food. Take w/ food or shortly after food. Swallow whole, do not divide.

Hypocalcaemia or serum Ca below the lower limit of the normal range. Concomitant use with etelcalcetide.

Patient with known congenital long QT syndrome, history of QT prolongation, family history of long QT syndrome or sudden cardiac death, impaired cardiac function; risk factors for gastrointestinal bleeding (e.g. gastritis, ulcers, oesophagitis, severe vomiting); history of seizure disorders. Smokers. Not indicated for use in chronic kidney disease (CKD) patients not on dialysis. Moderate to severe hepatic impairment. Pregnancy and lactation. Patient who started or discontinued concomitant therapy with strong CYP3A4 inhibitors or inducers. Patient Counselling This drug may cause dizziness and seizures; if affected, do not drive or operate machinery. Monitoring Parameters Monitor for signs and symptoms of hypocalcaemia at the start of therapy and regularly thereafter. For secondary hyperparathyroidism: Closely check serum Ca and phosphorus levels before and within 1 week after initiation, and frequently during dose titrations or adjustments; iPTH measurement 1-4 weeks after initiation or dose adjustments (wait at least 12 hours after a dose). Obtain serum Ca levels monthly after establishing the maintenance dose. For hypercalcaemia in parathyroid carcinoma or primary hyperparathyroidism: Closely monitor serum Ca levels before and within 1 week after initiation or dose titrations or adjustments. Obtain serum Ca levels every 2 months after establishing the maintenance dose.

Significant: QT prolongation and ventricular arrhythmia secondary to hypocalcaemia; hypotension, worsening of heart failure; seizure, gastrointestinal bleeding (mostly upper gastrointestinal bleeding) and ulcer, adynamic bone disease, reduced free testosterone concentrations; decreased level or temporary loss of consciousness. Blood and lymphatic system disorders: Anaemia. Gastrointestinal disorders: Nausea, vomiting, diarrhoea, dyspepsia, constipation, dysgeusia, abdominal pain. General disorders and administration site conditions: Asthenia, malaise. Immune system disorders: Hypersensitivity reactions (e.g. angioedema, urticaria). Metabolism and nutrition disorders: Hyperkalaemia, anorexia, decreased appetite. Musculoskeletal and connective tissue disorders: Myalgia, muscle spasms, back pain. Nervous system disorders: Headache, dizziness, paraesthesia. Psychiatric disorders: Insomnia. Respiratory, thoracic and mediastinal disorders: Upper respiratory tract infection, cough, dyspnoea. Skin and subcutaneous tissue disorders: Rash, pruritus. Vascular disorders: Hypertension.
Potentially Fatal: Hypocalcaemia.

Symptoms: Hypocalcaemia manifested by myalgia, paraesthesia, cramping, tetany, and seizures. Management: Symptomatic and supportive treatment.

Increased risk of hypocalcaemia with other agents known to reduce the serum Ca levels. Increased plasma concentration with strong CYP3A4 inhibitors (e.g. ketoconazole, itraconazole, telithromycin, ritonavir). Significantly increased exposure of drugs primarily metabolised by CYP2D6 (e.g. desipramine, nortriptyline, metoprolol, flecainide, propafenone, dextromethorphan).
Potentially Fatal: Concomitant use with etelcalcetide may result in severe hypocalcaemia.

Increased bioavailability and peak plasma concentrations with food. Plasma levels may be increased by grapefruit juice.

Cinacalcet is a phenylethylamine calcimimetic agent that binds to and increases the sensitivity of Ca-sensing receptors of the parathyroid glands to extracellular Ca. This activity lowers the PTH concentrations and leads to a concomitant decrease in serum Ca and phosphorus levels, thereby preventing progressive bone disease and complications associated with mineral metabolism disorders.
Absorption: Increased bioavailability and peak plasma concentrations with food. Absolute bioavailability: Approx 20-25% (fasted state). Time to peak plasma concentration: Approx 2-6 hours.
Distribution: Extensively distributed in the body. Volume of distribution: Approx 1,000 L. Plasma protein binding: Approx 93-97%.
Metabolism: Rapidly and extensively metabolised in the liver primarily by CYP3A4, CYP1A2, and CYP2D6 isoenzymes via oxidative N-dealkylation and oxidation of the naphthalene ring into inactive metabolites.
Excretion: Mainly via urine (approx 80% as metabolites); faeces (approx 15%). Elimination half-life: Approx 6 hours (initial); 30-40 hours (terminal).

Oral: Store between 15-30°C. Protect from light and moisture.

Other Agents Affecting Metabolism