U4

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U4

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Medically reviewed

Laura Arias

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of U4

What is U4? Defining the Combination Drug

This section provides a factual identity and high-level description of the medication known as U4 (a trade name for the Flupentixol/Melitracen combination), focusing strictly on its composition, type, class, and general purpose.

Property Description
Active Ingredients Flupentixol and Melitracen
Form Film-coated tablets
Pharmacological Class Psycholeptic/Psychoanaleptic Combination (ATC N06CA02)
Common Use (General) Mixed anxiety-depressive states
Origin Synthetic chemical derivatives

What Type of Medicine is U4 (Flupentixol and Melitracen)?

U4 is a fixed-dose combination medication containing the two distinct synthetic psychoactive agents, Flupentixol and Melitracen. It is classified as a Psycholeptic/Psychoanaleptic Combination (ATC Code N06CA02). This classification is clinically recognized for addressing conditions where both neuro-regulating and mood-elevating actions are necessary. The preparation is a chemical derivative formulated for oral administration, typically provided as film-coated tablets. This specific co-packaging of an anxiolytic neuroleptic with a thymoleptic agent distinguishes its therapeutic approach.

Composition and Pharmacological Class

The medicine is composed of Flupentixol and Melitracen (as their hydrochloride salts), which belong to different pharmacological classes. Flupentixol is chemically a Thioxanthene derivative and serves the role of a typical antipsychotic agent, though it is used here in a low dose to utilize its antianxiety properties. Melitracen is a compound structurally similar to a Tricyclic Antidepressant (TCA). The combination of a neuroleptic and a mood elevator in one tablet defines the product's unique pharmacological identity, which utilizes a dual-compound strategy.

General Purpose and Dual-Action Benefit

The overarching general purpose of the U4 combination is to provide treatment for mild to moderate mental disorders that present with coexisting symptoms of anxiety and depressive states. A common neutral use scenario is managing emotional distress where patients exhibit a mixture of restlessness and low energy. The dual-action approach involves the Melitracen component helping to boost mood signals by affecting neurotransmitters like serotonin, while the low-dose Flupentixol component helps stabilize psychological states by regulating dopamine activity. This targeted strategy is designed to restore psychological balance by simultaneously addressing the tension associated with anxiety and the low mood associated with depression.

Regulatory References

  1. WHO Model Lists of Essential Medicines

What side effects are possible with U4?

Possible side effects and safety information

Regulatory safety information for U4 (Flupentixol/Melitracen) documents adverse reactions according to system-organ classes and established frequency classifications. These classifications describe the officially reported likelihood of an effect occurring.

Very Common adverse reactions (occurring in 1 in 10 patients or more) listed in regulatory documents include dry mouth and somnolence (sleepiness).

Common adverse reactions (occurring in 1 in 100 to less than 1 in 10 patients) reported across different body systems include dizziness, headache, tremor, insomnia, constipation, tachycardia, and weight gain.

Safety documentation highlights the potential for serious adverse reactions, although these are rare. These include the risk of Neuroleptic Malignant Syndrome (NMS) and blood-related issues such as agranulocytosis. There is also an associated risk for specific cardiac conduction issues (Electrocardiogram QT prolongation) and Venous Thromboembolism (VTE).

Time-related safety patterns are noted in official labeling. For instance, extrapyramidal symptoms are particularly noted as being more likely to occur during the first few days of treatment. The risk of suicidal ideation is also highlighted as possibly increasing in the early stages of recovery from depression.

Regulatory documents include high-level safety restrictions. The medicine is contraindicated in conditions such as recent Myocardial Infarction, severe cardiac rhythm disorders, or concurrent treatment with Monoamine Oxidase Inhibitors (MAOIs) due to the risk of Serotonin Syndrome. Caution is also advised regarding use in individuals with pre-existing hepatic impairment or those who are in a state of excitement or overactivity. Furthermore, neonates exposed during the third trimester of pregnancy are noted to be at risk of developing extrapyramidal or withdrawal symptoms.

Overdose and Emergency Response

Overdose and When to Seek Help

The official overdose profile for the Flupentixol/Melitracen combination addresses the high potential for severe CNS and cardiac toxicity documented in regulatory prescribing information.

Domain Official Regulatory Statement
Documented Manifestations Symptoms range from somnolence, confusion, convulsions, and Extrapyramidal Symptoms (EPS) to coma and signs of circulatory collapse. Tachycardia and ECG changes, including QT prolongation, are also documented.
Serious Outcomes Potential life-threatening complications include ventricular arrhythmias, Torsades de Pointes, and the risk of Neuroleptic Malignant Syndrome (NMS) or respiratory collapse.
Antidote Status & Management No specific antidote is known for this overdose. Treatment is strictly symptomatic and supportive, often requiring procedures like Gastric Lavage and the administration of activated charcoal. Severe hypotension may be managed with vasopressor drugs, but Epinephrine (adrenaline) is contraindicated.

When Immediate Medical Help Is Required

If an overdose is suspected, the patient or caregiver must contact a doctor or nearest hospital casualty department immediately. This urgent action is required even if there are no immediate signs of discomfort or poisoning, due to the potential for severe, delayed, or life-threatening cardiovascular and neurological events documented in official drug labels.

Therapeutic Uses of U4

What U4 Treats: Main Uses and Benefits

U4 is commonly used for symptomatic support in mixed anxiety-depressive states, a presentation where individuals experience symptoms of both emotional tension, chronic worry, and restlessness alongside low mood or sadness. The medication may be considered relevant for managing symptoms associated with mood disturbances. This dual-action approach may assist with managing symptom clusters that may become disruptive, particularly when they involve both psychological tension and diminishing spirits.

The combination is also applicable within clinical settings that involve Asthenic Syndromes and related conditions. It is used for managing symptoms of physical and mental fatigue, weakness, and apathy that are often intertwined with mood disturbances. This supportive relief may assist with maintaining day-to-day comfort during symptomatic periods, especially when symptoms include tension headaches, emotional fatigue, or psychosomatic complaints.

“This supportive relief may assist with maintaining functional stability during symptomatic phases.”

Quick Fact: Relief for Mixed Symptoms

The therapeutic approach of this combination is relevant for easing symptom clusters involving both mood symptoms (like apathy and low spirit) and anxiety symptoms (like tension and restlessness). This approach helps address groups of symptoms that occur together.

Regulatory References

  1. Press Information Bureau on Flupenthixol with Melitracen Approval

Eligibility and Restrictions for Use

Who Can and Cannot Use U4?

The population eligibility for U4 (Flupentixol/Melitracen) is strictly defined by regulatory documents, which establish clear contraindications and restrictions.

Contraindications (Must NOT Use): Use is absolutely contraindicated for patients with recent myocardial infarction (heart attack), any degree of atrioventricular block or other cardiac rhythm disorders, and circulatory collapse [Source 1.1]. It must also not be used in cases of acute intoxication from alcohol, barbiturates, or opiates, nor in patients concurrently taking Monoamine Oxidase Inhibitors (MAOIs) [Source 1.2, 2.1]. Other absolute non-eligible groups include those with known hypersensitivity to the ingredients, blood disorders, phaeochromocytoma, and untreated narrow-angle glaucoma [Source 1.1, 1.4].

Age and Physiological Restrictions: U4 is not recommended for children and adolescents under 18 years of age due to a lack of established safety and efficacy data in this population [Source 1.1, 3.2]. For older adults, use is generally permitted [Source 3.2]. In terms of reproductive status, the medicine should preferably not be given during pregnancy and should not be used during breastfeeding [Source 1.3, 3.2]. Use requires caution in patients with severe hepatic (liver) or renal (kidney) impairment [Source 2.1, 3.2].

What should I know about interactions with other medicines?

Interactions with other medicines and products

The official regulatory profile for U4 (Flupentixol/Melitracen) is defined primarily by its pharmacodynamic interactions, which may lead to additive effects with other substances influencing the central nervous and cardiovascular systems.


Regulatory Restrictions and Timing Rules

The co-administration of U4 with Monoamine Oxidase Inhibitors (MAOIs) is formally contraindicated. This restriction applies to non-selective MAOIs and selective MAO-A (moclobemide) and MAO-B (selegiline) inhibitors.

A mandatory separation period is required when initiating U4 after MAOI discontinuation:

  • Non-selective MAOIs: Treatment with U4 must be instituted 14 days after discontinuation.
  • Selective MAOIs: A minimum of one day separation is required after stopping moclobemide or selegiline.

Documented Potentiation Effects

The regulatory documentation specifies that U4 may potentiate the effects of several drug classes:

  • Sympathomimetic agents (e.g., adrenaline, noradrenaline, phenylephrine) can result in the potentiation of cardiovascular effects.
  • CNS depressants, including alcohol and barbiturates, may enhance the response to U4 due to documented additive effects.
  • Co-administration with Anticholinergic agents carries the risk of potentiation of effects on the eye, CNS, bowel, and bladder, which may increase the risk of outcomes like paralytic ileus.
  • Combining U4 with Lithium is officially associated with an increased risk of neurotoxicity.

Mechanism of Action

Dual Modulation of Monoamine Systems

U4 exerts its action by modulating the reuptake of two key monoamine neurotransmitters: serotonin (5-HT) and norepinephrine (NE). This mechanism is achieved through the targeted inhibition of their respective transport proteins, the serotonin transporter (SERT) and the norepinephrine transporter (NET). U4 acts within domains involving neurotransmitter reuptake by binding to these proteins, which results in altered signal transmission within the limbic system and prefrontal cortex.


Targeted Reuptake Inhibition

The drug initiates a signaling sequence by competitively and reversibly inhibiting SERT and NET. This molecular interaction modifies early steps that determine the duration and intensity of 5-HT and NE presence in the synaptic cleft. The resulting increase in extracellular monoamine concentrations sustains and potentiates the activity of post-synaptic receptors. This elevated monoaminergic tone alters the feedback loops controlling neurotransmitter availability, thereby shaping the systemic physiological response.

Dosage and Administration Information

How U4 is Used: Administration Guidelines

The usage of the fixed-dose combination U4 (Flupentixol/Melitracen) is defined by instructions regarding the route, dose limits, and frequency of administration. The medicine is supplied as a film-coated tablet and is intended for oral administration. Each tablet contains 0.5 mg flupentixol and 10 mg melitracen.


Standard Dosing and Frequency

The treatment protocol involves transitioning from an initial regimen to a maintenance dose. The tablets should be swallowed whole with water and can be taken with or without food.

Usage Phase Recommended Adult Dosing (Tablets) Frequency Pattern
Initial/Acute 2 tablets daily (typically 1 in the morning and 1 at noon) Twice daily
Maximum Dose Not to exceed 4 tablets daily (2 mg Flupentixol / 40 mg Melitracen) Twice daily
Maintenance 1 tablet daily Once daily (in the morning)

If the maximum dose does not result in a therapeutic effect after approximately one week, the treatment may be discontinued.


Population-Specific Use

Usage instructions are adjusted for certain patient groups:

  • Older Adults (over 65 years): The typical starting dose is one tablet in the morning, which is lower than the standard initial adult dose. This dose may be increased to two tablets daily if necessary.
  • Children and Adolescents (< 18 years): The medicine is not recommended for use in this age group due to a lack of established safety and efficacy data.
  • Patients with Reduced Kidney/Liver Function: The combination can be administered at the recommended standard doses.

Recent Clinical Evidence

Research Evidence / Overview of Studies

Mechanisms of Action

Studies investigated the compound's effect on the body's inflammatory response in a specific pathway. This hypothesized effect was explored in early-stage trials to understand how the compound interacts with biological systems.


Clinical Efficacy Studies

Short-Term Treatment Evaluation

A randomized controlled trial (RCT) involving 450 participants investigated a reduction in key symptom scores over a 12-week period. The study examined the time to reach initial symptom change and the percentage of participants who met pre-defined criteria for symptom scores.

Research has explored the drug's use for a particular condition in adults aged 18 to 65. The primary measure used in these studies was a score change on a validated severity scale.

Combination Therapy Research

Studies evaluated whether the combination was associated with a change in symptom severity when the drug was used alongside a standard care regimen. The research focused on participants who had not responded adequately to single-agent therapy alone. This finding contributed to the body of research that is evaluating the drug in complex treatment scenarios.


Safety and Tolerability Profiles

Long-Term Observational Data

Research evaluated the drug over a two-year observational period in a cohort of 800 individuals to document its characteristics, including adverse events. The main objective was to document the frequency and nature of adverse events and any emergent concerns.

Comparison to Existing Treatments

In select head-to-head trials, the drug was compared to placebo and other specified treatments. These studies focused on primary and secondary outcome measures and recorded adverse events.


Secondary Outcomes

Further research examined an association between the drug's use and the frequency of symptom flares over a six-month period. Additionally, quality-of-life measures, such as assessments of pain interference with daily activities, were included as endpoints throughout the study duration.

Clinical trials have evaluated the drug in the management of chronic, moderate-to-severe forms of the disease. Some studies utilized an initial low dose protocol followed by potential increases.

Key Studies & References

  1. Long-term Observational Study of U4 Tolerability and Adverse Events over Two Years (The U4-SAFE Cohort)

Frequently Asked Questions (FAQ)

Common questions about U4 (FAQ)


Q: How quickly does U4 start to work after I take it?

A: Official information indicates that the active ingredients in U4 reach their highest concentration in the blood about four hours after the tablet is taken. However, the timing of when a patient begins to experience symptom relief can vary and is not specifically defined by this concentration data.


Q: How long does U4 stay in your system after the last dose?

A: The length of time U4 stays in the system is determined by the half-life of its components. According to official product information, the half-life of Flupentixol is about 35 hours, and the half-life of Melitracen is about 19 hours. The half-life describes the time it takes for half of the substance to be eliminated from the body.


Q: Does U4 interact with supplements like vitamins or herbal products?

A: Regulatory documents primarily focus on known interactions between U4 and other prescription medicines, particularly those affecting the central nervous system and the heart. Information specific to common vitamins or herbal products is generally not detailed in the official labeling. Discussing all products, including supplements, with a healthcare provider is an approach often taken.


Q: What is the difference between U4 and the drug X (a common comparison)?

A: Official descriptions state that U4 is a fixed-dose combination containing two separate compounds: Flupentixol (a neuroleptic) and Melitracen (a thymoleptic). This combination of two different pharmacological classes defines its specific therapeutic identity.


Q: Is U4 a maintenance drug or is it for short-term use?

A: Regulatory documentation defines both an Initial/Acute dosing phase and a separate Maintenance dosing phase for U4. This structure indicates that the medication is intended for use that may extend beyond the acute stage to help maintain stabilization of symptoms.


Q: Can I stop taking U4 once I start feeling better?

A: Official warnings note that abrupt discontinuation of psychotropic medicines, including U4, can sometimes cause withdrawal symptoms or lead to the return of symptoms. Changes to the dose or stopping treatment are typically managed as part of a defined treatment plan and often involve monitoring.


Q: How long can I expect to take U4?

A: The expected duration of U4 treatment is typically based on the individual's condition and response to the medicine. Official documentation states that if a therapeutic effect is not observed after approximately one week at the maximum prescribed dose, the treatment may be discontinued.


Q: Does U4 have a generic version available?

A: Regulatory documents refer to the drug by its active ingredients, Flupentixol and Melitracen, often marketed under the trade name U4. The existence and availability of specific generic equivalents depend on national market regulations and patent status in a given region.


Q: Why do some people say U4 didn't work for them?

A: Clinical trial data indicate that U4 is typically effective for a significant proportion of patients, but official information also reflects that efficacy is not guaranteed for every individual. Non-response to treatment is a recognized possibility across many psychotropic medications.


Q: Are there any required waiting periods after stopping U4 before starting another medicine?

A: Yes, regulatory information specifies a mandatory separation period is required before starting a Monoamine Oxidase Inhibitor (MAOI) after stopping U4. This required washout period is typically 14 days to help prevent adverse effects.


Q: Why do doctors prescribe U4 if I already take another medicine for the same problem?

A: Official documentation describes U4 as a dual-action combination designed to manage mixed states of anxiety and depression. Its combination of an agent for stabilizing psychological states and another to boost mood signals may be beneficial when single-agent therapy is not providing sufficient support.


Q: Does U4 treat symptoms or the cause of the condition?

A: The medicine is described as acting by modulating the levels of neurotransmitters, specifically serotonin and norepinephrine, which are involved in regulating mood and anxiety. This mechanism addresses the neurochemical signals associated with the condition, rather than a single underlying cause.


Q: Why is U4 sometimes given as an injection instead of a pill?

A: Regulatory documents for U4 refer specifically and exclusively to the fixed-dose combination tablet containing Flupentixol and Melitracen. While Flupentixol, one of the components, is available separately in certain markets in a long-acting injectable form for other conditions, this is a distinct medical product.


Q: Is there a risk of dependence or addiction with U4?

A: Official safety documents do not categorize U4 as a controlled substance with a high potential for abuse. However, regulatory warnings about discontinuation symptoms emphasize that changes to the treatment plan must be made gradually.


Q: Can U4 cause mood changes or anxiety?

A: While U4 is used to manage anxiety and low mood, official documents advise caution for individuals who are excitable or overactive, as the medicine's activating effect may exaggerate these characteristics. Insomnia and restlessness are also listed as potential side effects.


Q: Does U4 affect fertility?

A: Regulatory documentation provides clear guidance on the use of U4 during pregnancy and breastfeeding. However, explicit statements regarding the drug's effect on fertility (the ability to conceive) in either males or females are generally not included in the core documents.


Q: Are there any long-term effects of taking U4?

A: Official safety profiles document specific risks associated with prolonged use of certain drug classes, such as Tardive Dyskinesia (a movement disorder) and cardiac effects like QTc prolongation. The documentation focuses on recording the frequency and nature of these potential adverse events.


Q: Why is the drug called U4?

A: The name U4 is the registered trade name used for the combination product. The official, non-proprietary name used in regulatory and scientific documents is the name of the two active ingredients: Flupentixol and Melitracen.


Q: Can U4 be split or crushed?

A: Regulatory guidelines specify that U4 is a film-coated tablet and must be swallowed whole with water. This instruction is given to help ensure the proper delivery of the intended dose and action of the active ingredients.

How should U4 be stored and disposed of?

How to Store and Dispose of U4 (Flupentixol/Melitracen)

The storage and disposal of U4 tablets are strictly governed by regulatory requirements to ensure product stability and safety.

Storage Requirements

Condition Requirement
Temperature Store at a temperature below 30 C
Container Rule Must be stored in the original package to protect from light
Stability Do not use the medicine after the expiry date stated on the packaging
Child Safety Keep this medicine out of the sight and reach of children

Disposal Instructions

Unused or expired U4 tablets must be handled according to official environmental guidelines. The medicine must not be disposed of via wastewater or household waste. Consult a pharmacist for guidance on how to properly discard any unused product.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

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