Conivaptan vs Tolvaptan – Comparasion of Vaptans for Hyponatremia

Conivaptan

It is the generic name of a drug called conivaptan, that belongs to a group of drugs called vasopressin antagonists. It can be found under the brand name of Vaprisol.

Mechanism of Action

It works by raising the salt levels in the blood by removing extra body water as urine. This helps to increase the level of sodium in the blood.

Uses

This prescription medication is used to treat hyponatremia (low sodium levels).  Hyponatremia is defined as a sodium concentration of less than 135 mmol/L (135 mEq/L).

Low sodium can be caused by:

  • vomiting;
  • burns that affect a large area of the body;
  • sweating;
  • diarrhea;
  • syndrome of inappropriate antidiuretic hormone secretion;
  • liver cirrhosis;
  • kidney diseases;
  • heart failure;
  • diuretic medicines.

Dosage

This medication is injected into a vein through an IV, around-the-clock for 2 to 4 days.

The usual initial recommended dose is 20 mg IV once over 30 minutes, followed by 20 mg continuous IV infusion over 24 hours. The maximum recommended dose is 40 mg continuous IV infusion over 24 hours.

Side Effects

Common side effects may include:

  • mild dizziness;
  • fever;
  • redness or swelling around the IV needle;
  • low potassium;
  • headache.

Rare side effects may include:

  • seizure;
  • a feeling like you might pass out;
  • extreme thirst;
  • weakness in your arms and legs;
  • muscle weakness or limp feeling;
  • mood changes;
  • leg discomfort;
  • weakness;
  • trouble swallowing;
  • trouble speaking;
  • increased urination;
  • uneven heart rate.

Precautions

Before taking this vasopressin antagonist, tell your healthcare provider if you have:

  • HIV or AIDS;
  • congestive heart failure;
  • malnourishment;
  • liver disease;
  • a condition for which you take digoxin;
  • alcoholism;
  • kidney disease.

Alcoholalcohol

Avoid drinking alcoholic beverages while taking this vasopressin antagonist since alcohol use can substantially increase the risk of side effects.

Drug Interactions

It may negatively interact with other medications, especially:

  • irinotecan;
  • flibanserin;
  • uloric;
  • itraconazole;
  • fosamprenavir;
  • lomitapide;
  • idelalisib;
  • lovastatin;
  • imatinib;
  • lurasidone;
  • indinavir;
  • lopinavir;
  • irinotecan liposomal;
  • ketoconazole;
  • ivabradine;
  • isoniazid.

Pregnancy & Breastfeeding

It is not known whether this vasopressin antagonist passes into breast milk or if it could harm a nursing infant. You should not breastfeed a baby while you are receiving this medication.

It is not known whether this vasopressin antagonist will harm a developing fetus. Tell your physician if you are pregnant before using this medication.

Tolvaptan

It is the generic name of a drug called tolvaptan, that belongs to a group of drugs called vasopressin receptor blockers. It can be found under the brand name of Samsca.

Mechanism of Action

It works by raising salt levels in the blood by removing extra body water as urine.

Uses

This prescription medication is used in adults to help increase low sodium levels in the blood.

Dosage

The usual initial recommended dose is 15 mg orally once per day

The usual maintenance recommended dose is 30 mg once a day. The maximum recommended dose is 60 mg once a day.

Note – you should not use this medication for longer than 30 days.

Side Effects and Precautions

Common side effects may include:

  • weakness;
  • dry mouth;
  • constipation;
  • blurred vision;
  • drowsiness;
  • fruity breath odor;
  • hunger;
  • increased thirst or urination.

Rare side effects may include:

  • a seizure;
  • problems with speech or muscle control;
  • a light-headed feeling;
  • mood changes;
  • feeling very thirsty or hot;
  • trouble swallowing;
  • heavy sweating;
  • confusion;
  • jaundice (yellowing of the skin or eyes);
  • trouble moving your arms and legs;
  • dark urine;
  • upper stomach pain.

Contraindications

Before taking this vasopressin receptor blocker, tell your healthcare provider if you have:

  • a feeling like you might pass out;
  • are severely dehydrated;
  • are unable to tell that you are thirsty;
  • are unable to urinate.

Alcohol

Avoid drinking alcoholic beverages while taking this vasopressin receptor blocker since alcohol use can substantially increase the risk of severe side effects.

Drug Interactions

It may negatively interact with other medications, especially:

  • Tekturna (aliskiren);
  • Aldactone (spironolactone);
  • Procardia XL (nifedipine);
  • Bactrim (sulfamethoxazole/trimethoprim);
  • Heparin Sodium (heparin).

Pregnancy & Breastfeeding

It is not known whether this vasopressin receptor blocker will harm a developing fetus. Tell your physician if you are pregnant before using this medication

It is not known whether this vasopressin receptor blocker passes into breast milk or if it could harm a nursing infant. You should not breastfeed a baby while you are receiving this medication.

Bottom Line – Conivaptan vs Tolvaptan

Conivaptan (brand name – Vaprisol) is a medication which is used to treat hyponatremia (low sodium levels). It reduces the level of a hormone which regulates the balance of water and sodium in the human body.

Tolvaptan (brand name – Samsca) is a medication which is used to treat hyponatremia in people with certain hormonal imbalance and heart failure. It reduces the level of a hormone that regulates the balance of water and sodium in the body.

According to a 2010 study, both medications have limited data in heart failure patients, but have been shown to produce substantial decreases in body weight, pulmonary capillary wedge pressure, and symptoms of heart failure.

Overall, both are promising agents which can be used in hospitalized patients.

References

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2899773/
https://www.ncbi.nlm.nih.gov/pubmed/17664863
https://www.ncbi.nlm.nih.gov/pubmed/19057376

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