Usage
- Calcium phosphate is primarily used to prevent and treat calcium deficiencies. It’s also prescribed for conditions like hypocalcemia (low blood calcium) and osteoporosis (weak and brittle bones).
- Pharmacological classification: Mineral supplement, calcium replacement agent.
- Mechanism of action: Calcium phosphate provides a source of calcium and phosphate, essential minerals for bone formation, nerve function, muscle contraction, and other bodily processes. It works by supplementing dietary intake or correcting deficiencies to maintain optimal calcium and phosphate levels.
Alternate Names
- Tricalcium phosphate, calcium phosphate tribasic.
- Brand names: Posture, PhosLo (calcium acetate).
How It Works
- Pharmacodynamics: Calcium is vital for various physiological functions including bone mineralization, muscle contraction, nerve impulse transmission, blood clotting, and enzyme regulation. Phosphate plays a role in bone health, energy metabolism, acid-base balance, and cell signaling.
- Pharmacokinetics:
- Absorption: Calcium absorption from the gut is influenced by factors like vitamin D, dietary components, and the form of calcium supplement. Smaller doses (500 mg or less) are absorbed more efficiently. Food also enhances absorption, although calcium citrate is absorbed well with or without food.
- Metabolism: Calcium is not metabolized in the conventional sense. It is distributed throughout the body, with the majority stored in bones. Phosphate homeostasis is regulated by the kidneys, intestines, and bones, influenced by hormones like parathyroid hormone (PTH), vitamin D, and fibroblast growth factor 23 (FGF23).
- Elimination: Excess calcium and phosphate are excreted primarily by the kidneys.
Dosage
Standard Dosage
Adults:
- Prevention of deficiency: 1000-1200 mg of elemental calcium per day (equivalent to 2500-3000 mg of calcium phosphate). Divide doses if exceeding 600 mg of calcium.
- Treatment of deficiency: Determined by the prescriber based on the severity of the deficiency.
Children:
- Dosage varies depending on age:
- 1-3 years: 700 mg/day
- 4-8 years: 1000 mg/day
- 9-18 years: 1300 mg/day
- Pediatric safety considerations: Avoid exceeding the tolerable upper intake level (UL) to prevent adverse effects.
Special Cases:
- Elderly Patients: 1200 mg/day for women over 50 and men over 70. Monitor calcium levels and adjust dosage as needed.
- Patients with Renal Impairment: Careful monitoring and dosage adjustment are essential due to potential difficulties with calcium and phosphate excretion. Avoid calcium-based phosphate binders in patients with hypercalcemia or low PTH levels. Restrict total calcium intake to a maximum of 2000 mg/day, including dietary calcium.
- Patients with Hepatic Dysfunction: Generally, no specific dosage adjustment is required.
- Patients with Comorbid Conditions: Individualized assessment and dosage modification might be necessary.
Clinical Use Cases
Dosage recommendations for these settings aren’t standardized for calcium phosphate specifically and should be based on patient’s overall calcium status and clinical need.
- Intubation: Not specifically indicated.
- Surgical Procedures: Not specifically indicated.
- Mechanical Ventilation: Not specifically indicated.
- Intensive Care Unit (ICU) Use: Not specifically indicated.
- Emergency Situations: Not specifically indicated.
Dosage Adjustments
- Dose modifications are based on individual patient factors, including renal function, age, and concurrent medications. Monitor serum calcium and phosphate levels closely.
Side Effects
Common Side Effects
- Gastritis, nausea, vomiting, constipation, increased urination, increased thirst, dry mouth.
Rare but Serious Side Effects
- Hypercalcemia (high blood calcium), kidney stones, allergic reactions (hives, difficulty breathing, swelling).
Long-Term Effects
- Kidney problems, cardiovascular issues (with excessive intake).
Adverse Drug Reactions (ADR)
- Hypercalcemia requiring immediate intervention.
Contraindications
- Hypercalcemia, kidney stones, parathyroid gland disorders, sarcoidosis, malabsorption syndrome, hypersensitivity.
Drug Interactions
- Thiazide diuretics, antacids, vitamin D, certain antibiotics (quinolones, tetracyclines), iron supplements, thyroid medications, bisphosphonates, digoxin, levothyroxine.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: Not formally assigned. Considered a nutritional supplement generally safe in recommended amounts. Avoid exceeding the UL.
- Fetal risks: No known specific fetal risks.
- Breastfeeding: Calcium is present in breast milk. Supplement as needed to maintain maternal calcium levels.
Drug Profile Summary
- Mechanism of Action: Provides essential calcium and phosphate for bodily functions.
- Side Effects: Nausea, vomiting, constipation, hypercalcemia (high blood calcium).
- Contraindications: Hypercalcemia, kidney stones, parathyroid disorders.
- Drug Interactions: Thiazide diuretics, antacids, iron supplements, certain antibiotics.
- Pregnancy & Breastfeeding: Generally safe in recommended dosages.
- Dosage: Varies with age and condition; typically 1000-1200 mg/day for adults.
- Monitoring Parameters: Serum calcium, phosphate, PTH, creatinine.
Popular Combinations
- Calcium and vitamin D are often combined to enhance calcium absorption.
Precautions
- Monitor for hypercalcemia, especially in patients with renal impairment.
- Assess dietary calcium intake.
- Consider interactions with other medications.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Calcium Phosphate?
A: Varies by age and clinical indication. Adults generally require 1000-1200 mg of elemental calcium per day. Pediatric doses are lower and should be determined based on age.
Q2: What are the common side effects of Calcium Phosphate?
A: Common side effects include gastrointestinal issues like constipation, nausea, vomiting, and increased thirst and urination.
Q3: Who should not take Calcium Phosphate?
A: Individuals with hypercalcemia, kidney stones, or parathyroid gland disorders should avoid calcium phosphate.
Q4: Does Calcium Phosphate interact with other medications?
A: Yes, calcium phosphate can interact with certain medications, including some antibiotics, diuretics, and iron supplements.
Q5: Can Calcium Phosphate be taken during pregnancy?
A: Calcium phosphate is generally considered safe during pregnancy when taken within the recommended daily allowance.
Q6: How should Calcium Phosphate be taken?
A: It should be taken orally, preferably with food to improve absorption (except calcium citrate), and in divided doses if exceeding 600 mg of elemental calcium at a time.
Q7: What is the role of Vitamin D in Calcium Phosphate absorption?
A: Vitamin D is crucial for enhancing calcium absorption in the gut. Supplementation with vitamin D is often recommended alongside calcium phosphate.
Q8: What should I monitor in patients taking Calcium Phosphate?
A: Monitor serum calcium, phosphate, and PTH levels, as well as kidney function, to avoid potential complications like hypercalcemia and renal impairment.
Q9: Can I take Calcium Phosphate with iron supplements?
A: Calcium can interfere with iron absorption. Take these supplements at least two hours apart.
