Haloperidol

BRAND NAMES

Brand names of haloperidol include Haldol and Serenace, though many other brands exist globally. 

• Haldol-The original brand name used for haloperidol in the U.S. and other countries. It is available in various forms, including oral tablets, oral solution, and injections.

• Serenace-A widely known brand, especially in the UK and India.

   

MECHANISM OF ACTION

Haloperidol is thought to work by competitively blocking post-synaptic dopamine (D2) receptors in the brain. This action reduces dopamine neurotransmission, which helps alleviate delusions and hallucinations commonly linked to psychosis.

PHARMACOKINETICS

Absorption

Haloperidol is efficiently absorbed from the gastrointestinal tract when taken orally; however, first-pass metabolism in the liver reduces its oral bioavailability to between 40% and 75%.

Distribution:

Haloperidol is heavily protein bound in human plasma, with a free fraction of only 7.5 to 11.6%. Haloperidol is a highly lipophilic (fat-soluble) antipsychotic drug with a large volume of distribution that spreads extensively throughout the body's tissues

Metabolism:

It is extensively metabolized in the liver, with less than 1% of the unchanged drug eliminated in the urine.

Excretion:

Haloperidol is extensively metabolized in the liver, with most of the drug being eliminated from the body as metabolic by products through both the kidneys (urine) and the liver (bile). Only about 1% of the administered dose is excreted unchanged in the urine.

PHARMACODYNAMICS

The pharmacodynamics of haloperidol involve its potent antagonism of dopamine D2 receptors in the brain, which is responsible for both its therapeutic effects and many of its characteristic side effects. As a typical, or first-generation, antipsychotic, it primarily acts on the dopamine system, with minimal activity at serotonin receptors.

ADMINISTRATION

Haloperidol is available for oral use as tablets and an oral concentrate, and it also comes in a nasal spray form. For parenteral administration, haloperidol lactate is a short-acting solution given by intramuscular or intravenous injection, while haloperidol decanoate is a long-acting formulation intended for intramuscular use.

DOSAGE AND STRENGTHS

Haloperidol is widely used internationally and comes in multiple formulations. For oral administration, it is available in tablet strengths of 0.5 mg, 1 mg, 2 mg, 5 mg, and 10 mg, as well as an oral concentrate with a strength of 2 mg/mL. A nasal spray formulation is also available. For parenteral use, haloperidol lactate is provided as a short-acting solution at 5 mg/mL for intramuscular injection. The long-acting depot form, haloperidol decanoate, is administered intramuscularly using the Z-track technique.

DRUG INTERACTIONS

Haloperidol has notable drug interactions, mainly related to its impact on the heart’s electrical activity, its potential to cause central nervous system (CNS) depression, and its hepatic metabolism. These interactions can heighten the risk of serious adverse effects, including life-threatening cardiac arrhythmias and profound sedation.

FOOD INTERACTIONS
Alcohol should be avoided, as it may enhance the risk of hypotension and central nervous system (CNS) side effects.

CONTRAINDICATIONS

Haloperidol is contraindicated in individuals with Parkinson’s disease, dementia with Lewy bodies, those in a comatose state, or anyone with significantly depressed central nervous system (CNS) function. Since many medications—such as barbiturates, benzodiazepines, and opioids—can also cause CNS depression, combining them with haloperidol should be avoided or undertaken with great caution.

SIDE EFFECTS

• Dizziness or low blood pressure: If you feel lightheaded, stop your activity and sit or lie down until the sensation passes.

• Constipation: Increase your intake of dietary fiber by eating more fresh fruits, vegetables, and whole grains, and ensure you're drinking plenty of water.

• Dry mouth: Stay hydrated and consider chewing sugar-free gum or sucking on sugar-free candies to stimulate saliva.

• Blurred vision: This may occur temporarily; take care when reading or performing tasks that require clear vision.

• Drowsiness or sleepiness: You may feel unusually tired—avoid driving or operating heavy machinery if affected.

• Difficulty sleeping (insomnia): Try to maintain a regular sleep routine and avoid stimulants like caffeine close to bedtime.

OVER DOSE

• A sudden increase in blood pressure

• Drowsiness or sedation

• In severe cases, coma can develop alongside respiratory depression and marked hypotension

• Although rare, serious ventricular arrhythmias may occur, regardless of whether there is a prolonged QT interval or not

TOXICITY

The most significant toxic effects of haloperidol include severe extrapyramidal symptoms, low blood pressure, and sedation. In severe cases, the patient may become comatose and experience profound respiratory depression or shock due to hypotension. Extrapyramidal symptoms can manifest as akathisia, muscle rigidity, slowed movements (bradykinesia), tremors, and acute dystonia.