Promethazine is a drug that belongs to the group of phenothiazines. But unlike other substances in this group, it is a low-potency neuroleptic, which is why it is not usually used as such. In most cases, promethazine is used to treat allergies and as a sedative. Although its properties can be used in the treatment of many other conditions and diseases.

What is Promethazine?

Promethazine is an active ingredient whose empirical formula is C17H20N2S and belongs to the group of phenothiazines. Theoretically it is a neuroleptic, but due to its mechanism of action it actually belongs to the group of drugs used to treat complications from allergic reactions.

Therefore, promethazine can be defined as a depressant, anticholinergic, and antiallergic. This medication can be administered orally, parenterally, rectally, and topically.

What is Promethazine tablets and drops for?

The promethazine in either of its two presentations, is used for allergy treatments and as an antiemetic. Although it has little or no use as an antipsychotic, which is unusual for a neuroleptic, it is used quite frequently as a sedative. This medication is also prescribed for:

  • Restlessness and agitation in the context of psychiatric disorders
  • Anxiety disorders
  • Allergic diseases
  • Sleep disorders
  • Nausea and vomiting
  • Insect bites, skin irritations, sunburns

Promethazine is used to treat allergies

One of the effects of promethazine that is used regularly in medicine is its antihistamine effect. Histamine is a messenger substance that plays an important role in allergic reactions. By blocking histamine receptors, the stimuli transmitted by histamine are no longer transmitted. This helps against allergic reactions, but also relieves nausea and has a calming and sleep-stimulating effect.

Promethazine for the treatment of sleep disorders

The active ingredient has a calming and sleep-stimulating effect by targeting special binding sites in the body, the so-called receptors. Interaction with these binding sites blocks the effect of the body’s own messenger substance, which, among other effects, stimulates sleep.

In cases of sleep disorders, this medicine should only be used if the sleep disorder is serious and cannot be remedied in the short term by other measures, such as eliminating the cause.

Promethazine serves for restlessness and agitation

Promethazine also binds to histamine receptors found in the central nervous system. Due to this binding, this active substance has a calming effect, thus making it a particularly suitable element for the therapy of restless and agitated conditions in different types of patients, including patients with psychiatric disorders.

Promethazine is used for nausea and vomiting

One of the alternatives for the treatment of nausea and vomiting is the use of dopamine antagonists. In this sense, promethazine has all the qualities for the treatment of such complications, especially in cases of hyperemesis gravidarum in pregnant women.

Promethazine for the treatment of psychosis and schizophrenia

Promethazine acts as an antipsychotic in the central nervous system. It blocks the dopamine receptor or docking sites for the nerve messenger substance, dopamine, so that it can no longer bind and develop its effect.

Excess dopamine leads to loss of reality, psychosis, and schizophrenia. Therefore, antipsychotics can counteract the loss of reality. However, the active ingredient promethazine has a weak antipsychotic effect – about 50 percent of the potency of the parent substance chlorpromazine.

Promethazine dosage

The dose and duration of treatment with promethazine depend on the type and severity of the disease. Therefore, the patient should always visit his doctor before starting treatment with this drug.

Promethazine drop dose

Promethazine drops should be taken with plenty of liquid, for example a full glass of water.

Drop dose for allergic reactions

Adults should start treatment with 30 to 50 drops. Then you should take 10 to 20 drops up to four times a day and 20 drops at night.

In the case of children and adolescents, it begins with ten to 20 drops. Afterwards, five to ten drops are taken up to three times a day and ten to 20 drops at night.

The maximum daily dose is 0.5 milligrams of promethazine (20 drops contain approximately 20 milligrams) per kilogram of body weight.

Dose for restlessness and agitation

In the context of psychiatric illness, adults start with 20 to 30 drops at night. If necessary, the intake can be increased to a maximum of five doses of 20 drops per day.

In very severe cases, the dose can be briefly increased to five doses of 40 drops per day.

Dosage in cases of nausea and vomiting

When other therapies don’t help, adults should start with 20 to 30 drops. Afterwards, they should take 10 to 20 drops three times a day.

Children and adolescents start with ten drops. Afterwards, they should take five drops three times a day or ten drops twice a day.

Dose in sleep disorders

Adults should take 20 to 50 drops in the evening and children and adolescents can take 10 drops in the evening. In both cases the maximum daily dose (0.5 milligrams of promethazine) should not be exceeded.

Promethazine tablet dosage

Promethazine tablets should be taken with plenty of fluids, as should the drops.

Tablet dosage for restlessness and agitation

Adults should initially take one 25-milligram tablet in the evening. If necessary, the dose can be increased to up to four tablets. In severe arousal states, the dose can be increased in the short term up to eight coated tablets per day.

Dosage in tablets in cases of nausea and vomiting

Adults should take a 25-milligram tablet. Treatment is generally continued with up to two tablets daily.

Tablet dosage for sleep disorder

Adults should take up to two tablets in the evening. In elderly and debilitated people, as well as in patients with brain disease, circulatory and respiratory weakness or liver and kidney disorders, the dose should be reduced.

Contraindications and warnings in the use of promethazine

Promethazine  and use of machinery

Promethazine may impair the ability to drive or operate machinery that pose a risk to the integrity of the patient. This alteration is especially greater when Promethazine is taken in combination with alcohol or other medications.

Promethazine in children

The drug is contraindicated to be administered in children under 2 years of age.

People with allergies to its components

Any allergies to the active substance, to its excipients, to other medicines, in particular to sulphites and to medicines similar to promiase, such as chlorpromazine, fluphenazine, mesoridazine, perphenazine, prochlorperazine, thioridazine or trifluoperazine, or any food.

Promethazine and other medicines

Medications and herbal supplements that the patient is currently taking, mainly in substances such as atropine, benzatropine, belladonna, dimenhydrinate, scopolamine, blood pressure medications, anticoagulants, bronchodilators, bladder or urination medications, monoamine oxidase inhibitors, medicines for Parkinson’s or gastric ulcers or irritable bowel syndrome

Promethazine and some health history

Consider the use of promethazine if the patient suffers or has suffered from asthma, COPD, sleep apnea or other respiratory problems, seizures, immune depression, glaucoma, prostatic hypertrophy or urination problems, ulcers, gastric obstruction, heart disease or high blood pressure, and hypocalcaemia.

Promethazine in pregnancy

Women who have a confirmed pregnancy or those who are in control to become pregnant, or while breastfeeding, cannot take this medicine.

In conclusion the use of Promethazine is very varied

As we have seen, the use of Promethazine is extremely varied, as it has demonstrated its efficiency both in psychiatric events, as well as in cases of allergy and sleep disorders, among others. But it also has some important contraindications, therefore, its use must be strictly indicated by a doctor.

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Dr. Samantha Robson ( CRN: 0510146-5) is a nutritionist and website content reviewer related to her area of ​​expertise. With a postgraduate degree in Nutrition from The University of Arizona, she is a specialist in Sports Nutrition from Oxford University and is also a member of the International Society of Sports Nutrition.

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