Tolvaptan 15 mg Tablets – Complete Guide for Treating Hyponatremia & ADPKD

🔹What Is Tolvaptan 15 mg Used For?

Tolvaptan 15 mg is used in the treatment of:

1. Hyponatremia (low blood sodium levels)

Caused by:

• Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)
• Heart failure
• Liver cirrhosis

2. Autosomal Dominant Polycystic Kidney Disease (ADPKD)

To slow the progression of kidney cyst development and preserve kidney function.

🔹How Tolvaptan Works

Tolvaptan is a selective vasopressin V2 receptor antagonist. It works by:

• Blocking the action of vasopressin, a hormone that causes water retention
• Promoting aquaresis — excretion of free water without losing sodium or potassium
• In ADPKD, reducing cAMP signaling in renal cells, thus slowing cyst growth and kidney damage

🔹Dosage and Administration

🔸 For Hyponatremia (Samsca®):

• Starting dose: 15 mg once daily
• May be increased to 30 mg or 60 mg based on clinical response and sodium levels

🔸 For ADPKD (Jinarc®):

• Used as part of a split-dose regimen (e.g., 45/15 mg, 60/30 mg, 90/30 mg)
• 15 mg tablets are commonly used as the lower evening dose or for titration

Administration:

• Take orally once a day (or twice daily in split-dose)
• Can be taken with or without food
• Should be taken in the morning to reduce nighttime urination

🔹Benefits of Tolvaptan 15 mg

• Effectively raises serum sodium levels
• Improves symptoms of hyponatremia (e.g., confusion, lethargy)
• Slows the progression of ADPKD, delaying the need for dialysis
• Oral once-daily or split-dosing convenience

🔹Common Side Effects

System Affected	Common Symptoms
Renal/Urinary	Frequent urination, increased thirst
GI	Nausea, dry mouth, constipation
Nervous system	Dizziness, headache
Metabolic	Dehydration, electrolyte imbalances

🔹Serious Side Effects (Monitor Closely):

• Liver toxicity (increased AST, ALT, bilirubin)
• Rapid sodium correction (risk of osmotic demyelination)
• Hypernatremia
• Severe dehydration or low blood pressure

💡 Liver function tests are required regularly, especially in ADPKD patients.

🔹Warnings & Precautions

• Do not use in patients with an inability to perceive or respond to thirst
• Not recommended for hypovolemic hyponatremia
• Avoid in patients with liver disease unless essential
• Requires hospital initiation for hyponatremia due to risk of overcorrection
• Avoid use during pregnancy and lactation

🔹 Drug Interactions

Drug Type	Effect
CYP3A4 inhibitors (e.g., ketoconazole)	Increase tolvaptan levels (avoid)
CYP3A4 inducers (e.g., rifampin)	Reduce tolvaptan effectiveness
Diuretics	May increase dehydration or electrolyte loss
Grapefruit juice	Inhibits metabolism, increases drug exposure

🔹Liver Monitoring (Especially in ADPKD)

Tolvaptan can cause serious liver damage, particularly in long-term use for ADPKD. Monitoring protocol:

• Baseline liver tests before starting
• Monthly monitoring for first 18 months
• Then every 3 months thereafter
• Discontinue if signs of liver injury appear

🔹Storage Instructions

• Store at 20–25°C (68–77°F)
• Protect from moisture, heat, and direct sunlight
• Keep in original packaging and out of reach of children

🔹Patient Tips

• Stay hydrated but avoid overhydration — follow physician advice
• Monitor for signs of liver problems: yellowing skin, dark urine, abdominal pain
• Do not skip liver function tests if used for ADPKD
• Report any signs of overcorrection of sodium (e.g., seizures, confusion)