Parathyroid hormone parenteral
- Drugs List
- Therapeutic Indications
- Dosage
- Administration
- Contraindications
- Precautions and Warnings
- Pregnancy and Lactation
- Side Effects
- Monograph
Presentation
Parenteral formulations of parathyroid hormone.
These products have been produced by recombinant technology using E.coli.
Drugs List
Therapeutic Indications
Uses
Hypoparathyroidism
Adjunctive treatment of chronic hypoparathyroidism not adequately controlled with standard therapy alone.
Dosage
The aim of parathyroid hormone (PTH) therapy is to reach a target serum calcium concentration range of 2.0 to 2.25 millimoles per litre pre-dose, and less than 2.55 millimoles per litre 8 to 12 hours post-dose. This should be achieved by a combination of regular monitoring of serum calcium concentration during the titration and dose adjustment periods, and consequent adjustment of PTH dosage, and any calcium or active vitamin D supplementation.
Adults
Initiation
50 micrograms daily. If pre-dose serum calcium is above 2.25 millimoles per litre, consider 25 micrograms as a starting dose.
In patients using active vitamin D, decrease the dose of active vitamin D by 50% if pre-dose serum calcium is above 1.87 millimoles per litre. In those using calcium supplements, maintain calcium supplement dose.
When applying dosage adjustments, adjust PTH dosage first, vitamin D dosage second, and finally supplemental calcium third. Adjust the dosage of these components in combination until target pre-dose serum calcium concentration is within the range of 2.0 to 2.25 millimoles per litre, vitamin D has been discontinued and calcium supplementation is sufficient to meet daily requirements.
During initiation, PTH dose increments should only be considered if pre-dose serum calcium is lower than 2 millimoles per litre, and patient has had a stable dose for at least 2 to 4 weeks. Maximum PTH dose of 100 micrograms daily.
Dose adjustments after initiation period
The dosage of PTH may be increased in 25 microgram increments approximately every 2 to 4 weeks, to a maximum daily dosage of 100 micrograms, provided pre and post-dose serum calcium are within an acceptable range.
Downward titration can occur at any time, to a minimum of 25 micrograms.
At any dose level of PTH, if post-dose serum calcium exceeds the upper limit of normal and all active vitamin D and oral calcium have been withheld, or symptoms suggesting hypercalcaemia are present, the dose of Natpar should be reduced.
Additional Dosage Information
Missed dose
If a dose of PTH is missed, the dose should be administered as soon as possible, and additional active vitamin D and supplemental calcium should be taken based on symptoms of hypocalcaemia.
Administration
For subcutaneous injection only.
Parathyroid hormone should be injected daily in the thigh (alternate thigh every day).
Contraindications
Children under 18 years
Risk factors for osteosarcoma
Unexplained elevations of alkaline phosphatase
History of radiotherapy to the skeleton
Malignant bone disease
Skeletal metastasis
Precautions and Warnings
Patients over 65 years
Young adults
Breastfeeding
Pregnancy
Severe hepatic impairment
Severe renal impairment
Urolithiasis
Ensure adequate vitamin D and calcium supplementation
Exclude pseudohypoparathyroidism before treatment
Treatment to be initiated and supervised by a specialist
Record name and batch number of administered product
Self-admin. - only if adequately trained and have access to expert advice
Monitor serum calcium at initiation and dose adjustments
Monitor serum magnesium before and during treatment
Monitor serum vitamin D levels before and during treatment
Monitor calcium + adjust supplementation after discontinuation/interruption
Monitor serum calcium levels regularly from starting treatment
Advise patient to report signs of hypocalcaemia
Discontinue if severe hypersensitivity reactions occur
Parathyroid hormone should be used with caution in young adults with open epiphyses, as these patients may be at an increased risk of osteosarcoma.
If severe hypercalcaemia occurs (greater than 3.0 millimoles per litre, or above the upper limit of normal with symptoms), ensure adequate hydration and consider interruption of PTH, calcium and vitamin D until serum calcium returns to the normal range. Consider resuming PTH, calcium and vitamin D at lower doses.
Monitoring of pre-dose and post-dose serum calcium levels, as well as adherence to the dosage recommendations, minimises the risk of hypocalcaemia, hypercalcemia, and tachyphylaxis.
Risk of serious hypocalcaemia is highest after Natpar is withheld, missed or abruptly discontinued.
Pregnancy and Lactation
Pregnancy
Use parathyroid hormone with caution during pregnancy.
At the time of writing, there are no adequate data from the use of parathyroid hormone in pregnant women. The manufacturer states that full consideration of the associated risks and benefits must be undertaken before the use of parathyroid hormone during pregnancy, as a risk of harm to the pregnant woman or developing foetus cannot be excluded. No harmful reproductive effects were observed in animal studies.
Parathyroid hormone is not thought to cross the placenta, due to its high molecular weight.
Schaefer (2015) states that parathyroid hormone may be used in pregnancy, provided maternal serum calcium levels are appropriately monitored. Although in the rare case of hyperparathyroidism in pregnancy there were no reports of foetal damage, hypercalcaemia may affect the foetus.
Lactation
Use parathyroid hormone with caution during breastfeeding.
The manufacturer states that full consideration of the associated risks and benefits must be undertaken before the use of parathyroid hormone in breastfeeding. It is not known whether parathyroid hormone is excreted in human breast milk. Animal lactation studies have shown excretion of parathyroid hormone in milk.
Side Effects
Anxiety
Arthralgia
Asthenia
Chest pain
Cough
Diarrhoea
Extremity pain
Fatigue
Headache
Hypercalcaemia
Hypercalciuria
Hypersensitivity reactions
Hypertension
Hypoaesthesia
Hypocalcaemia
Hypomagnesaemia
Injection site reactions
Insomnia
Muscle spasm
Muscle twitch
Musculoskeletal pain
Myalgia
Nausea
Neck pain
Palpitations
Paraesthesia
Pollakiuria
Possible alteration in tests for parathyroid function
Seizures
Somnolence
Tetany
Thirst
Upper abdominal pain
Vomiting
Overdosage
It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.
The following number will direct the caller to the relevant local centre (0844) 892 0111
Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
Further Information
Last Full Review Date: March 2020
Reference Sources
Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 3rd edition (2015) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.
Summary of Product Characteristics: Natpar 25mcg, 50mcg, 70mcg and 100mcg per dose powder and solvent for solution for injection. Shire pharmaceuticals limited. Revised July 2019.
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