Periactin 1%

Cyproheptadine

Method of action: Antiallergic, Antiserotonin

Treatment option: Allergic Reactions, Allergic Conjunctivitis, Anaphylaxis, Angioedema, Vasomotor Rhinitis, Dermatographia, Hives, Cold, Rhinitis, Pink Eye

Medically reviewed

Rosario Oropesa

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 Periactin 1%

Property	Description
Active ingredient	Cyproheptadine hydrochloride
Form	Liquid (Solution or Syrup)
Pharmacological class	First-generation Antihistamine and Antiserotonergic agent
General purpose	Antiallergic action and Appetite stimulation
Origin	Synthetic compound

Identity and Core Classification of Cyproheptadine

The active medicinal component in this preparation is the synthetic compound Cyproheptadine, which is formally classified as a first-generation antihistamine and a potent serotonin 5-HT2 receptor antagonist. This classification arises from its unique chemical structure as a piperidine derivative. Unlike newer antihistamines, Cyproheptadine is noted for its ability to non-selectively antagonize both histamine H1 receptors and serotonin receptors. This dual action is characterized by efficacy as both an H1 antagonist and a serotonin antagonist in clinical settings.

Composition and Meaning of the 1% Formulation

The medicine’s specific identity, designated as Periactin 1%, refers to a formulation containing Cyproheptadine hydrochloride at a precise one percent concentration. This percentage and the product name specify a liquid dosage form, such as an oral solution or syrup, utilizing an aqueous or hydroalcoholic vehicle for systemic delivery. This liquid presentation is a key differentiating feature, often preferred for ease of precise measurement, distinguishing it from the standard solid oral tablet form. The product is a single-ingredient product, containing only Cyproheptadine as the principal active therapeutic agent, without the addition of other therapeutic compounds.

High-Level Purpose and General Action

The compound's function is recognized for its ability to serve as an antiallergic agent by blocking histamine activity, which helps reduce symptoms triggered by allergic responses, such as irritation. In addition to this anti-histaminic property, the agent's unique action on serotonin receptors grants it a characteristic orexigenic property, meaning it has a general ability to stimulate appetite, particularly in certain patient groups. Cyproheptadine has an established use as an antihistaminic agent with recognized secondary effects on appetite.

Regulatory References

National Library of Medicine

What side effects are possible with Periactin 1%?

Possible Side Effects and Safety Information

This section describes the officially documented adverse reactions and safety characteristics of cyproheptadine, the active ingredient in Periactin 1%, as defined by governmental regulatory documents.

Adverse Reaction Scope and Classification

The most commonly classified adverse reactions, designated as Common (1% to 10%), involve the Central Nervous System. These primarily include drowsiness, sedation, and somnolence, effects that are often noted as transient and may lessen after the initial period of continuous use. Other documented adverse events affect various System-Organ Classes, including the Gastrointestinal System (e.g., dry mouth, constipation, vomiting), the Cardiovascular System (e.g., palpitation, hypotension), and the Hepato-biliary System.

Serious Adverse Reactions and Safety Constraints

Official labeling documents list serious adverse reactions that have been reported. These include hepatic failure, hepatitis, jaundice, convulsions (seizures), and anaphylactic shock. The medicine's safety profile defines strict limitations on its use. It is contraindicated in individuals experiencing an acute asthmatic attack, those with narrow-angle glaucoma, or gastrointestinal obstruction. Use is also strictly contraindicated when taking Monoamine Oxidase Inhibitors (MAOIs), as this combination intensifies anticholinergic effects.

Population-Specific Safety Considerations

Regulatory documents highlight specific constraints for certain populations. The use of cyproheptadine is contraindicated in Newborn or Premature Infants and in Nursing Mothers. Elderly patients are noted to be more susceptible to adverse effects such as dizziness, sedation, and hypotension. In Children, there is an officially documented risk of paradoxical excitation (increased agitation and restlessness) instead of the expected sedation.

Overdose and Emergency Response

The official regulatory profile for an overdose of Cyproheptadine, the active ingredient in Periactin 1%, documents a wide spectrum of potentially severe manifestations affecting the Central Nervous System (CNS) and cardiovascular function. Documented signs include dual CNS effects, ranging from profound depression, excessive drowsiness, and the potential for coma, to CNS stimulation characterized by excitement, restlessness, and convulsions. These neurological effects are often coupled with significant anticholinergic symptoms, such as dilated pupils (mydriasis), dry mouth, and fever (hyperpyrexia).

Severe outcomes documented in official labeling include cardiac arrhythmias, profound hypotension, and the risk of respiratory arrest or cardiac arrest. Pediatric patients are noted in the regulatory guidance as being particularly susceptible to the severe excitatory effects.

The official regulatory instruction for any suspected overdose is to seek immediate medical attention. This action is mandated due to the risk of life-threatening events, such as a seizure, collapse, or difficulty breathing. Treatment is officially defined as symptomatic and supportive, as no specific antidote is known. Regulatory procedures described for emergency management include the potential for gastric lavage or the administration of activated charcoal, with mandatory ECG monitoring and observation.

Therapeutic Uses of Periactin 1%

The liquid formulation of Cyproheptadine is commonly used across domains where additional symptomatic support is needed, addressing a range of allergic and nutritional concerns. Its therapeutic applications span several acute and chronic conditions.

This medication is generally used to help with symptoms related to inflammatory or irritative states, such as the acute manifestations of allergic rhinitis, allergic skin conditions like urticaria (hives) and angioedema, and is considered relevant for easing symptoms related to recurrent vascular headaches. It helps address symptom clusters that may become intense or disruptive, including persistent itching, sneezing, and runny nose. It provides support that helps ease the overall symptom burden and contributes to easing the overall symptom load during periods of heightened symptoms.

The medicine is also commonly applied in clinical settings where additional symptomatic support is needed to address lack of appetite. It is relevant for pediatric patients and others to help manage insufficient weight gain associated with conditions presenting with episodes of anorexia (lack of appetite). This supportive use provides supportive relief when symptoms interfere with routine activities by supporting caloric intake.

“This medication is commonly used across conditions presenting with acute episodes, providing symptomatic relief that may help patients cope more steadily with symptom fluctuations.”

Quick Fact: Supportive Role in Pruritus and Hives
This therapeutic application is relevant for managing skin discomfort where symptoms are driven by inflammatory or irritative processes.

Regulatory References

NIH MedlinePlus Drug Information

Eligibility and Restrictions for Use

This information is strictly based on governmental regulatory documents regarding official eligibility and non-eligibility for this medicine, which contains cyproheptadine.

Who Should Not Use Periactin 1% (Contraindications)

The medicine is formally contraindicated and should not be used in several patient groups and clinical situations:

Infants: Newborn or premature infants.
Nursing Mothers: Use is prohibited due to the potential for serious adverse reactions in the nursing baby.
Concomitant Medications: Individuals taking Monoamine Oxidase Inhibitors (MAOIs) due to the risk of intensifying anticholinergic effects.
Specific Conditions: Patients diagnosed with narrow-angle glaucoma, a stenosing peptic ulcer, pyloroduodenal obstruction, symptomatic prostatic hypertrophy, or bladder neck obstruction.
Older Adults: The drug is also contraindicated for use in elderly or debilitated patients.

Age-Related and Restricted Use

Population	Eligibility Classification	Restriction Context
Pediatric Patients (under 2 years)	Safety and effectiveness not established	Use is not supported by current data.
Elderly Patients	Contraindicated/Use with caution	Dose selection should be cautious, starting at the low end of the range.
Pregnancy	Use only if clearly needed	The drug is classified as Pregnancy Category B.

Special Consideration

The medicine should be used with caution in patients with a history of bronchial asthma, increased intraocular pressure, hyperthyroidism, cardiovascular disease, or hypertension. Use is not recommended in cases of renal insufficiency, where elimination is reduced.

What should I know about interactions with other medicines?

Official Documented Interactions

The official regulatory labeling for cyproheptadine defines a specific profile of documented interactions, categorized primarily by pharmacodynamic effects and mandated restrictions.

Contraindicated Combinations

Co-administration with Monoamine Oxidase Inhibitors (MAOIs) is formally prohibited. This restriction exists because MAO inhibitors prolong and intensify the anticholinergic effects of cyproheptadine, as explicitly stated in the prescribing information. No specific numerical timing rule for separation is documented, but concurrent use is restricted.

Pharmacodynamic Interaction Categories

Regulatory documents identify several categories of substances that produce additive effects with cyproheptadine:

CNS Depressants: Antihistamines are documented as having additive effects with other Central Nervous System (CNS) depressants, including sedatives, tranquilizers, anti-anxiety agents, and hypnotics.
Alcohol: The official labeling identifies alcohol as having an additive effect, increasing the overall CNS depressant action when co-administered.
Serotonin-enhancing Agents: The anti-serotonin activity of cyproheptadine may interfere with the function of serotonin-enhancing anti-depressants. This interaction is noted in official monographs as potentially resulting in a recurrence of depression.

The interaction structure is defined by the necessity of avoiding combinations that intensify anticholinergic risk or increase CNS depression, reflecting the official regulatory cautions for this medication.

Mechanism of Action

Periactin (cyproheptadine) exerts its effects through the antagonism of multiple key receptors, primarily modulating the activity of neurotransmitters and specific chemical mediators active in both peripheral and central nervous systems.

Histamine H1 Receptor Antagonism

This constitutes the primary mechanistic domain, where the compound acts as a competitive H1-receptor antagonist. It blocks the binding of histamine to its receptor sites on effector cells in various tissues, including the gastrointestinal tract, blood vessels, and respiratory structures. This inhibition affects downstream signaling sequences initiated by H1 receptor activation.

Serotonin Receptor Modulation

Cyproheptadine engages mechanisms involving serotonin (5-HT) signaling, functioning as an antagonist at 5-HT receptors, notably the 5-HT2A and 5-HT2C subtypes. This action modifies signaling sequences downstream of 5-HT receptor activation in targeted neural and peripheral pathways.

Muscarinic Acetylcholine Receptor Blockade

The compound also acts as an antagonist at certain muscarinic acetylcholine receptors (e.g., M1). This anticholinergic activity modulates signaling within pathways associated with the parasympathetic nervous system, influencing downstream physiological parameters.

Dosage and Administration Information

Administration Instructions

This medicine is administered exclusively by the oral route as either a tablet or an oral solution (syrup). The medicine is typically taken two or three times a day in divided doses. It should be taken at approximately the same time(s) every day to maintain a consistent schedule.

Dosing and Regimen Rules

Dosing is individualized and based on the patient's size and response.

Age Group	Recommended Initial Daily Dose	Maximum Daily Dose
Adults	4 mg, three times a day	32 mg/day or 0.5 mg/kg/day
Children (7-14 years)	4 mg, two or three times a day	16 mg/day
Children (2-6 years)	2 mg, two or three times a day	12 mg/day

For elderly patients (65 years and older), it is generally recommended to use the lower end of the dosage range or to administer the dose less frequently. The safety and effectiveness of this medicine in children under the age of two years have not been established, and it should not be given to newborn or premature infants.

Administration Procedures

Tablets: Swallow the tablet whole with a full glass of water.
Oral Solution (Syrup): The liquid form must be measured using a specialized measuring device (e.g., a dosing cup, spoon, or syringe). Do not use a household spoon, as it may not provide an accurate dose.

If a dose is missed, take it as soon as it is remembered. However, if it is almost time for the next scheduled dose, skip the missed dose and continue the regular dosing schedule. Do not take a double or extra dose to make up for a missed one.

Recent Clinical Evidence

Research Evidence / Overview of Studies for Periactin 1%

Evidence for Use in Appetite Stimulation and Weight Gain

The active component, Cyproheptadine, has been studied in research settings exploring outcomes related to insufficient weight gain and appetite loss. These investigations include Randomized Controlled Trials (RCTs) and systematic reviews, primarily examining pediatric patients with chronic conditions. Researchers examined changes in Body Mass Index (BMI), weight, and patient-reported appetite scores. Findings describe patterns observed in the studies where weight measurements changed over the typically limited study periods, which often spanned only a few weeks to months.

Evidence for Use in Allergic Conditions

The research base for Cyproheptadine was studied in the context of allergic conditions, supported by historical clinical trial data. Studies explored the medication's use in conditions like urticaria (hives) and allergic rhinitis, with researchers monitoring validated symptom severity scores and outcomes related to physical discomfort. The historical context of this use means initial clinical data is available for review. However, contemporary research often focuses on patients whose symptoms remained despite use of other allergy medications, highlighting a current comparative evidence gap against modern standard-of-care treatments for patients starting therapy.

Study Duration, Patient Groups, and Uncertainty

The majority of pivotal studies for both applications focused on short- or intermediate-term effects, with follow-up durations that were limited. Long-term effects are not fully established regarding sustained patterns of appetite or weight stability. The available evidence specifically includes pediatric patients across various age groups, reflecting a significant area of research. In contrast, data for certain groups remain insufficient, notably the systematic evidence exploring the use of this medicine in the older adult population experiencing appetite loss.

Overall, the research landscape highlights several areas where certainty remains low. Evidence quality varies across studies due to heterogeneity in findings, and comparative evidence is lacking in dedicated recent trials.

Key Studies & References

Frequently Asked Questions (FAQ)

Common questions about Periactin 1% (FAQ)

Q: Does Periactin 1% require a prescription from a doctor?

Yes, Periactin 1%, which contains the active ingredient cyproheptadine, is classified as a prescription-only (Rx) medication. Regulatory status indicates that it can only be obtained with a valid prescription from a licensed healthcare provider.

Q: Can Periactin 1% be taken by people with kidney problems?

Official guidance notes that the elimination of this medicine is reduced in cases of renal insufficiency, which is the term for reduced kidney function. Regulatory caution notes that elimination may be impaired in this condition, and that cautious dose selection is advised in the official documentation.

Q: What do studies show about Periactin 1% causing a feeling of increased hunger?

Official summaries of adverse events list increased appetite as a reported side effect of this medicine. Additionally, the drug is officially recognized for its orexigenic property, which means it has a general tendency to stimulate appetite.

Q: Does Periactin 1% cause weight changes, according to regulatory data?

Weight gain is listed among the documented side effects of the medicine in official regulatory data. This is described as a potential effect in authoritative drug information.

Q: Can Periactin 1% be safely used during pregnancy, according to official sources?

According to official sources, the medicine is classified as Pregnancy Category B. Official guidance indicates that its use during pregnancy is warranted only when a healthcare provider determines the need clearly outweighs the potential risks.

Q: Is Periactin 1% known by any other brand names?

Periactin is a brand name for the active ingredient, Cyproheptadine. This active ingredient is also widely available in generic forms, which are sold under the chemical name Cyproheptadine.

Q: Is Periactin 1% the same as other antihistamines available over the counter?

This medicine is classified as a first-generation antihistamine that requires a prescription. This makes it distinct from many common, newer over-the-counter (OTC) antihistamines, which are often second-generation and do not require a prescription.

Q: Are there any specific foods or drinks that should be avoided with Periactin 1%?

Official product information indicates that the medicine may be administered without regard to meals. Interactions with alcohol, however, are specifically addressed and cautioned against in the main Interactions section.

Q: What if I experience unusual or severe side effects while using Periactin 1%?

In the event of severe or concerning symptoms, contacting emergency medical services or a national poison help center is the recommended course of action for immediate, expert instructions.

Q: Can Periactin 1% be used by people who have asthma or lung conditions?

Regulatory documents advise caution when the medicine is used in individuals with a history of bronchial asthma or other lung conditions. This caution is related to the anticholinergic effect, which may cause a reduction in bronchial secretions.

Q: Does the time of day matter when taking Periactin 1%?

The required dosing schedule involves taking multiple, divided doses throughout the day. Because the medicine commonly causes drowsiness and sedation, individuals often schedule their doses to account for this potential effect.

Q: Is it acceptable to use Periactin 1% if I have a history of heart issues?

Regulatory documents advise caution when the medicine is used in individuals with a pre-existing history of cardiovascular disease or hypertension (high blood pressure). Regulatory caution is specifically advised in these populations.

Q: Do studies suggest any impact of Periactin 1% on attention or focus?

Official warnings describe common Central Nervous System (CNS) effects that include drowsiness and dizziness. Less common reported effects also include potential confusion or impaired cognition, which may affect attention and focus.

Q: What happens if I accidentally take more Periactin 1% than intended?

In the event of accidentally taking more than the intended amount, contacting emergency services or a poison help center is the recommended action to receive immediate, expert instructions.

How should Periactin 1% be stored and disposed of?

Official Storage and Disposal Guidelines

Cyproheptadine Hydrochloride Oral Solution must be stored at Controlled Room Temperature, which is 20 C to 25 C (68 F to 77 F), with permitted excursions up to 30 C. The liquid formulation must be protected from freezing, excess heat, and moisture. The product must be kept in its original, tightly closed, light-resistant container and stored strictly out of the reach of children.

Disposal Requirements

Official disposal instructions recommend using a drug take-back program as the preferred method for discarding unused or expired medication. If a take-back program is unavailable, the medication may be disposed of in household trash after mixing with an undesirable substance, such as coffee grounds, and sealing it in a plastic bag. Regulatory bodies explicitly state that this medication must not be flushed down the toilet or poured down a drain.

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

Available in countries:

Japan

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