Levomepromazine: Formula, Presentation, Indications, Mechanism of Action, Dosage and Side Effects

It is a phenothiazine with pharmacological activity similar to that of chlorpromazine and promethazine.

It possesses the antagonistic properties to the histamine of the antihistamines, together with the effects on the central nervous system that resembles chlorpromazine.

The place of action is the thalamus, the hypothalamus, the reticular system, and the limbic system. The sensory impulses are eliminated, which causes sedation and an increase in the threshold of pain and amnesia.

This is a phenothiazine with a pharmacological activity mainly due to its antagonism to dopamine receptors in the brain.

Chemical formula

  • C19H24N2OS.


  • Levomepromazine maleate 25 mg tablets.


Its use is mainly indicated in the control of conditions that present psychotic symptoms such as hallucinations, delusions, and confusion.

As it would be the cases of schizophrenia, bipolar disorder, mania, and confusional organic syndromes (delirium) and in conditions that involve agitation and psychomotor excitement such as:

Dementia and anxiety, depressive states, acute and chronic psychosis, and severe and drug intoxication.


In addition, these types of antipsychotics are used as antiemetics and in some movement disorders, such as Tourette’s syndrome.

It works by helping to restore certain natural substances in the brain.

It can help to think clearly and participate in daily life.

It is also used to treat anxiety disorders, sleep disorders, nausea, vomiting, and pain.

This medicine has calming, relaxing, and analgesic effects.

Mechanism of action

It is a sedative antipsychotic that acts on the central nervous system as dopamine antagonists at the D2 receptors.

It is a sedative with marked adrenolytic and anticholinergic properties.


In adults, the oral administration of levomepromazine in problems such as mild or moderate psychopathies, the initial dose is 6 to 12 mg per day.

In patients with severe, rebellious, refractory, relapsing psychopathies with great agitation and excitement, the recommended dose is 50 to 150 mg per day.

The maximum oral dose of levomepromazine is 300 mg in 24 hours.

It is recommended to initially administer a low dose and increase it progressively until it reaches optimal therapeutic levels.

Once the desired therapeutic effect has been obtained, it is recommended to gradually reduce it until the minimum effective dose is reached.

When you start taking the medication for the first time, the doctor can indicate the division of the dose and take the medication 2 to 3 times per day.

After taking the medication for a while, the doctor can indicate taking medicine in a single dose. Usually, that does take it at bedtime.

The doctor’s instructions must be followed carefully.

The dosage will depend on the medical condition, age, and the response to the treatment that the patient can give.

In children, the dosage should also be based on body weight.

If the drowsiness produced by this medication is a problem for the patient, the doctor may indicate a lower dose during the day and a higher amount before going to bed.

If you are using the liquid formulation of this medicine, you should carefully measure the dose with a device such as a syringe or a special measuring spoon.

Do not use a spoon for domestic use, as the exact dose may not be obtained.

It is convenient to take it simultaneously every day to avoid forgetting the dose.

You should take this medication regularly to get the most benefit expected from it. It would help if you did not stop taking it without consulting your doctor, as some conditions may worsen when the medication stops suddenly.

The dose may occasionally need to be decreased gradually.

Side effects

Levomepromazine can cause dizziness, lightheadedness, drowsiness, constipation, dry mouth, blurred vision, difficulty urinating, and weight gain.

If any of these effects persist or worsen, you should inform the doctor immediately.

To relieve symptoms such as dry mouth, you should consume sugar-free candy or finish pieces of ice, chew gum without sugar, and drink plenty of water.

Dizziness and lightheadedness may increase the risk of falls.

The patient should be lifted slowly when he is in a sitting or lying position.

The doctor may indicate that the patient stays in bed for one to two days at the start of treatment with this medication for the first time until the body becomes accustomed to it and dizziness subsides.

The doctor should be informed immediately of the appearance of any of these side effects:

  • Spasm or muscle stiffness.
  • The tremors.
  • The restlessness
  • The facial expression is similar to a mask.
  • Drooling

The doctor may recommend another medication to be taken together with levomepromazine to decrease these side effects.

Many patients who use this medication do not have serious side effects.

This medicine can raise your blood sugar level, which can cause or worsen diabetes, but they are implausible effects.

The doctor should be told immediately if you have symptoms associated with high blood sugar levels, such as increased thirst and frequent urination.

If the patient has diabetes, their blood sugar level should be monitored. Depending on the results, the doctor may recommend a medication adjustment for diabetes, an exercise program, or a diet.

This medication can increase a particular natural substance, such as prolactin, produced by the body.

In women, this increase in prolactin results in the segregation of breast milk, periods of suspension or interruption, or difficulties in becoming pregnant.

In men, it can cause a decrease in sexual capacity, the inability to produce sperm, or an increase in the size of the breasts.

Rarely can men have a painful or prolonged erection that lasts more than 4 hours?

If this occurs, you should stop taking this medication and get medical help immediately, or permanent problems may arise.

Levomepromazine can rarely cause a disease known as tardive dyskinesia.

But in some cases, this condition can be permanent, which is why you should see the doctor immediately if you develop symptoms such as:

Unusual or uncontrollable movements, especially on the face, lips, mouth, tongue, arms, or legs.

Rarely this medication can cause a severe condition called neuroleptic malignant syndrome.

Medical attention should be obtained immediately if the patient has any of the following symptoms, such as:

  • Intense tiredness
  • Severe confusion
  • Pain.
  • Weakness.
  • Fever.
  • Sensitivity.
  • Excessive sweating
  • Fast, irregular heartbeat.
  • Presence of dark urine.
  • Muscular stiffness.
  • Signs of kidney problems, such as changes in the amount of urine.

Tell your doctor immediately if you have any severe side effects, such as bleeding or easy bruising, or signs of infection such as:

  • Fever.
  • Persistent sore throat.
  • Sickness.
  • Vomiting
  • Frequent loss of appetite.
  • Stomach or abdominal pain.
  • Yellow eyes and skin.

Among the severe side effects include:

Pain, swelling, sudden redness, fainting, severe dizziness, seizures, persistent diarrhea, blood or mucus in the stool.

Severe allergic reactions to this medicine are rare.

Immediate medical attention should be sought if the appearance of any symptoms is noted, including rash, itching, swelling of the face, tongue, and throat, severe dizziness, and difficulty breathing.

Warnings and contraindications

Do not take levomepromazine if you are allergic to it, or other phenothiazines, such as chlorpromazine, or if you suffer from allergic processes to other substances, such as inactive ingredients.

Nor should this medicine be administered when the patient presents:

  1. Blood problems include low white blood cell count, low platelets, anemia, brain tumors, or tumors.
  2. Severe problems in the central nervous system and liver diseases.
  3. Problems of the adrenal gland ( pheochromocytoma ).
  4. Eye problems such as glaucoma, heart problems such as anginaheart attack, fast or irregular heartbeat, Parkinson’s disease, seizures, difficulty urinating, and prostate disorders.

Levomepromazine can affect the heart rhythm ( prolongation of the QT interval is observed in the electrocardiogram ).

Rarely, it can cause rapid and irregular heartbeat, very infrequently fatal, and symptoms such as the presence of intense dizziness or fainting. Still, if they occur, they require immediate medical attention.

The risk of a prolonged QT interval may be increased if the patient has certain medical conditions or is receiving treatment with other medications that cause QT prolongation.

The use of this medication is restricted if the patient has any of the following conditions:

  • The presence of specific heart problems such as heart failure.
  • Presence of slow heartbeats.
  • The prolongation of the QT interval in the electrocardiogram.
  • Medical history of family history with particular heart problems.

The risks of prolonging the QT intervals may increase with low levels of potassium or magnesium in the blood.

This risk may increase with certain medications such as diuretics or water pills if the patient has severe sweating, diarrhea, or vomiting.

Because this medication can have side effects such as dizziness, drowsiness, or blurred vision.

It is not recommended to drive vehicles, use machinery or perform activities that require alertness or a clear vision until you are sure you can perform these activities safely.

The use of alcoholic beverages should be avoided.

This drug can cause sensitivity to sunlight, causing photosensitivity, so you should limit the time to the sun while you are being treated with levomepromazine.

Tanning booths and solar lamps should be avoided.

Sunscreen and protective clothing should be worn when outdoors.

The doctor should be informed immediately if he is exposed to the sun, receives burns or blisters, or redden the skin.

This drug can decrease sweating, making the patient more prone to heatstroke.

Avoid doing things that may cause you to overheat, such as hard work or exercise in hot climates.

When it is hot, the body should be kept hydrated, drinking plenty of fluids.

If persistent fever, mental and mood changes, headaches, or dizziness occur, caution should be exercised before undergoing procedures with markers such as specific X-ray procedures or undergoing surgeries.

The liquid forms of this product may contain sugar and alcohol.

Caution is advised in the case of patients suffering from diabetes, alcohol dependence, or liver disease.

Geriatric patients are usually more sensitive to the side effects of this medication, especially drowsiness, dizziness, lightheadedness, difficulty urinating, severe constipation, and prolongation of the QT interval.

Drowsiness, dizziness, and lightheadedness may increase the risk of falls in this type of patient.

If the patient is pregnant or is planning a pregnancy, you should know about the benefits and risks of using this medication during pregnancy.

The use of this medication during pregnancy should be done only when necessary, and the benefits outweigh the risks.

Cases have been reported of babies born to mothers who have used this drug during the last three months of pregnancy, have presented but with rare occurrence symptoms, such as the presence of muscle stiffness or tremors, drowsiness, difficulty eating, or breathing, presence of constant crying.

The doctor should be informed immediately if these symptoms are noticed in the newborn, mainly during the first month of life.

As it is unknown if this medication passes into breast milk or may have undesirable effects on the infant, it is recommended to stop breastfeeding.

Untreated mental and mood problems such as schizophrenia and bipolar disorder can be severe conditions, so you should not stop taking this medication without a prescription.


Interactions with other medications can change the functioning of drugs or increase the risk of severe side effects.

This medication is not recommended to be used concomitantly with drugs such as levodopa.

Drugs such as levomepromazine can affect the heart rate causing ventricular tachycardia (prolongation of the QT interval), including dronedarone and pimozide, among others.

When you go to the doctor, you should be told if you are taking other products that cause drowsiness, such as:

  • Opiates or analgesics such as codeine, hydrocodone, and alcohol.
  • Medications for sleep or anxiety such as alprazolam, lorazepam, and zolpidem.
  • Muscle relaxants such as carisoprodol, cyclobenzaprine .
  • Antihistamines such as cetirizine , diphenhydramine .

Other medications for allergies or cough and cold products should be reviewed because they may contain ingredients that cause drowsiness and prevent concomitant use.