Drug information of Phenindione

Phenindione


An indandione that has been used as an anticoagulant. Phenindione has actions similar to warfarin, but it is now rarely employed because of its higher incidence of severe adverse effects.

Mechanism of effect

Phenindione inhibits vitamin K reductase, resulting in depletion of the reduced form of vitamin K (vitamin KH2). As vitamin K is a cofactor for the carboxylation of glutamate residues on the N-terminal regions of vitamin K-dependent proteins, this limits the gamma-carboxylation and subsequent activation of the vitamin K-dependent coagulant proteins. The synthesis of vitamin K-dependent coagulation factors II, VII, IX, and X and anticoagulant proteins C and S is inhibited. Depression of three of the four vitamin K-dependent coagulation factors (factors II, VII, and X) results in decreased prothrombin levels and a decrease in the amount of thrombin generated and bound to fibrin. This reduces the thrombogenicity of clots.

Pharmacodynamic

Phenindione thins the blood by antagonizing vitamin K which is required for the production of clotting factors in the liver. Anticoagulants such as Phenindione have no direct effect on an established thrombus, nor do they reverse ischemic tissue damage (damage caused by an inadequate blood supply to an organ or part of the body). However, once a thrombus has occurred, the goal of anticoagulant treatment is to prevent further extension of the formed clot and prevent secondary thromboembolic complications which may result in serious and possibly fatal sequelae.

Pharmacokinetics

Absorption: Absorbed slowly from the gastrointestinal tract.

Protein binding: 88%

Metabolism: Hepatic.

Half life: 5-10 hours

Dosage

Adults

  • usual starting dose of 200mg on the first day
  • after the first day, the dose is usually reduced to 100mg a day.

 

From the third day of treatment, the doctor will adjust your dose up or down depending on the results of the blood test which will be performed at the start and at regular intervals during your treatment.

children

Phenindione  Tablets are not suitable for use in children.

Alerts

  • if you have a painful skin rash. On rare occasions Phenindione Tablets can cause serious skin conditions, including one called calciphylaxis that can start with a painful skin rash but can lead to serious complications. This adverse reaction occurs more frequently in patients with chronic kidney disease
  • if you are elderly
  • if you have recently lost or gained a lot of weight
  • if you have any short term illness
  • if you have a problem with your kidneys or liver which is not classed as severe
  • if you are being sick or have diarrhea
  • if you are changing your diet which may result in an increase or decrease of Vitamin K
  • if you have protein C or S deficiency (blood clotting disorders)
  • if you have a disease of the brain and blood vessels (cerebrovascular disease)
  • if you have major heart disease
  • if you have low levels of iron in the blood (which may lead to pale appearance of the eyes and skin)
  • if you have had a major injury
  • if you have ulcers in your stomach
  • if you have bleeding in the stomach or intestines
  • if you have either an increase or decrease in the levels of thyroid hormone
  • if you have cancer
  • if you have decreased blood supply to a part of the brain (ischemic stroke)
  • if you are going to have surgery. The doctor may have to change your dose or stop your Phenindione treatment
  • if you have stopped smoking.

 

Points of recommendation

  • Phenindione Tablets contain lactose which is a form of sugar. If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicinal product.
  • Always take this medicine exactly as your doctor or pharmacist has told you.
  • Swallow the tablets whole with a drink of water
  • Try to take the tablets at the same time each day
  • If you miss a dose and remember within two or three hours, you can still take that dose. If you forget for a longer time, do not take that dose to catch up, but take your next dose when it is due. Remember to tell your doctor when you see him/her next and have your blood test. Do not take a double dose to make up for a forgotten tablet.
  • Do not stop taking your tablets except on your doctor’s advice as your condition may worsen.


Comments
    No comments yet.

Ask a Pharmacist

Related drugs