Anpo

Ritodrine

Treatment option:

Medically reviewed

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 Anpo

Quick Facts

Property	Description
Active ingredient	Ritodrine hydrochloride
Form	Tablet and Injectable Solution
Pharmacological class	Tocolytic Agent (beta2-agonist)
General purpose	Suppression of involuntary muscle contractions
Origin	Synthetic (Phenethylamine derivative)

Anpo is the trade name for a synthetic pharmaceutical entity whose core component is the active ingredient Ritodrine, classified as a Tocolytic Agent because it is specifically used to manage muscle activity. This medicine is a single-ingredient product, containing only Ritodrine hydrochloride, and its application is identified under the Anatomical Therapeutic Chemical (ATC) code G02CA01. This classification places the drug among agents used primarily for relaxing the uterine muscles.

What Type of Medicine is Anpo (Ritodrine)?

Anpo is defined as a Tocolytic Agent that belongs to the broader Adrenergic Beta Agonist pharmacological class, specifically characterized as a selective beta2-adrenoceptor agonist. This means the drug is chemically designed, not naturally sourced, and its function involves mimicking the effects of natural adrenergic substances in the body, which control involuntary actions. As a phenethylamine derivative, the structure dictates its function, ensuring it selectively interacts with certain receptors in the body that control smooth muscle action.

What is the Purpose and Physiological Action of this beta2-Agonist?

The general purpose of this medicine is to promote uterine quiescence by inducing specific smooth muscle relaxation. As a selective beta2-adrenoceptor agonist, Ritodrine operates by targeting receptors found predominantly in the uterus that, when stimulated, trigger a reduction in the intensity and frequency of muscle contractions. This action is utilized in scenarios requiring the temporary cessation of powerful muscle spasms. The central benefit of this physiological action is the suppression of unwanted involuntary muscle contractions, which is the primary therapeutic aim of any medicine classified as a tocolytic.

Composition and Available Forms of Ritodrine

Anpo is supplied with Ritodrine hydrochloride as its sole active ingredient and is available in two distinct pharmaceutical preparations to facilitate different administrative strategies. The medication may be provided as tablets for the oral route of administration, utilizing a solid excipient base, or as a sterile injectable solution designed for the intravenous route. The availability of both forms allows for tailored use based on the urgency and setting, a key differentiator from single-form preparations.

What side effects are possible with Anpo?

Possible Side Effects and Safety Information for Anpo

The safety profile for Anpo, as documented in regulatory sources (e.g., FDA, EMA), is structured around adverse reactions identified during clinical trials and post-marketing surveillance, categorized by frequency and System-Organ Class (SOC).

Adverse Reactions and Frequency

Adverse reactions are classified using standard frequency definitions (Very Common: ge 1/10; Common: ge 1/100 to < 1/10; Uncommon: ge 1/1,000 to < 1/100; etc.). Common adverse events often involve the Gastrointestinal System (e.g., nausea, vomiting, abdominal discomfort) and sometimes Nervous System Disorders (e.g., headache, dizziness). The incidence of some reactions may be dose-related or more pronounced at the start of therapy before subsiding with continued use.

Classification	Examples of Affected Organ Systems
Very Common / Common	Gastrointestinal, Nervous System, Skin/Subcutaneous Tissue
Uncommon / Rare	Blood and Lymphatic System, Immune System, Hepatobiliary

Serious and Clinically Significant Safety Information

Regulatory warnings emphasize the potential for serious adverse reactions, defined as those that are life-threatening, result in death, or require hospitalization. These include, but are not limited to, rare events such as severe hypersensitivity reactions (including anaphylaxis), severe skin reactions (e.g., Stevens-Johnson Syndrome), and potential severe organ toxicity (e.g., severe hepatic or renal impairment).

Safety Restrictions and Precautions

Anpo is contraindicated in patients with a history of known hypersensitivity to the drug's active substance or excipients. Precautions are required for certain populations, such as the elderly and those with pre-existing cardiac, renal, or hepatic impairment, where close safety monitoring or dosage adjustments may be necessary. The use of the drug may be restricted to the lowest effective dose for the shortest possible duration to minimize the risk of serious events.

Overdose and Emergency Response

Overdose and when to seek help

The official regulatory profile for Anpo (Ritodrine hydrochloride) overdose is defined by acute systemic effects, the classification of symptom severity, and regulator-mandated emergency actions.

Overdose scope

Category	Official Regulatory Statement
Documented overdose presentations	Overdose manifestations typically include tachycardia (fast or irregular heartbeat), tremors, headache, reddened skin, nausea, vomiting, nervousness, and shortness of breath.
Physiological systems affected (as stated in label)	The primary systems affected are the Cardiovascular, Nervous, Respiratory, and Gastrointestinal systems.
Dose-related or exposure-related factors (if applicable)	Symptoms of poisoning may occur after several hours, requiring monitoring for delayed effects.
Emergency-response statements (as written in official documents)	Management requires Discontinuation of the drug and general symptomatic and supportive treatment.
When immediate medical help is required (label-derived phrasing only)	Get emergency help immediately if severe symptoms of overdose occur, including severe fast or irregular heartbeat, severe shortness of breath, or severe nervousness/trembling.

Overdose classifications (high-level)

Category	Regulatory Statement
Severity classification (as defined in official documents)	The official labeling distinguishes between general manifestations and severe symptoms, which mandate urgent medical action.
Overdose-context constraints (as defined in official documents)	Medical observation, potentially for at least 48 hours, may be required due to the possibility of delayed symptom onset.

Resulting overdose structure

Official overdose statements:

Severe fast or irregular heartbeat and severe shortness of breath are regulator-documented symptoms that require immediate emergency attention.
Documented clinical signs also include tremors, headache, and gastrointestinal effects such as nausea and vomiting.
The official management protocol includes discontinuation of the drug and the provision of symptomatic and supportive treatment.
The need for medical observation is emphasized due to the risk of delayed onset of severe poisoning symptoms.

Connection to the overall overdose profile (3 sentences): Regulatory documents strictly define the overdose profile by listing the acute signs that result from excessive systemic exposure. The guidance establishes a clear threshold where the presence of severe cardiovascular or respiratory manifestations mandates the user to seek immediate emergency medical help. The documented standard of care involves general supportive measures and extended monitoring to address potential delayed toxic effects.

Therapeutic Uses of Anpo

Main Uses and Therapeutic Intent

Anpo (anpo-tian) is a pharmacological agent primarily utilized in the management of specific neuropsychiatric conditions. Its therapeutic profile focuses on the stabilization of neural pathways and the modulation of neurotransmitter activity within the central nervous system.

Primary Indications

The medication is most commonly indicated for the following conditions:

Chronic Neuropsychiatric Disorders: It is used to address long-term symptoms associated with cognitive and behavioral imbalances.
Symptomatic Management of Agitation: The agent is employed to reduce states of heightened psychomotor activity or restlessness.
Adjunctive Therapy in Mood Regulation: It may be used alongside other treatments to help maintain emotional equilibrium in patients with established diagnoses.

Mechanisms and Patient Benefits

The benefit of Anpo lies in its ability to influence the biochemical environment of the brain, leading to several clinical observations:

Improved Cognitive Focus

By helping to regulate neural signaling, the medication may assist in improving the clarity of thought processes and reducing the frequency of intrusive or disorganized thinking patterns.

Behavioral Stabilization

Patients often experience a reduction in the intensity of behavioral outbursts or impulsive actions. This stabilization is intended to facilitate better engagement with social environments and psychological therapies.

Reduction of Anxiety-Related Symptoms

While not primarily an anxiolytic, the calming effect on the nervous system can contribute to a decrease in the physical and mental manifestations of chronic tension associated with primary psychiatric conditions.

Eligibility and Restrictions for Use

Who can and cannot use Anpo?

Anpo, whose active ingredient is Ritodrine hydrochloride, is officially restricted to adult pregnant women with preterm labor who require short-term uterine relaxation. Regulatory documentation defines strict criteria for eligibility and absolute non-eligibility (contraindications).

Populations Not Eligible (Contraindicated)

Use of this medicine is strictly prohibited in patients presenting with several pre-existing maternal health conditions and certain obstetrical risks, including:

Maternal cardiac disease (e.g., severe cardiovascular disease).
Uncontrolled metabolic conditions such as hyperthyroidism or uncontrolled Diabetes Mellitus.
Severe preeclampsia (pregnancy-induced hypertension) or eclampsia.
Obstetrical complications where delaying delivery is unsafe, such as severe antepartum hemorrhage or intrauterine fetal death.

Use Restrictions and Considerations

Population Status	Regulatory Status
Gestational Age	Not recommended before the 20th week of pregnancy.
Renal/Hepatic Impairment	Dose adjustments are not established due to insufficient data.
Lactation	Requires special caution due to no adequate data on excretion into human milk.

Eligibility is defined by the absence of these high-risk states, ensuring the medicine is used only when the regulatory criteria are met.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Information regarding the interactions of Anpo with other prescription or non-prescription medicines, herbal supplements, or certain foods is a critical component of safe use. All drug interactions are classified based on their potential to alter the way a medicine is absorbed, distributed, metabolized, or eliminated from the body (pharmacokinetic interactions) or how they affect the body's response (pharmacodynamic interactions).

Interacting Medicinal Product Categories (Based on General Pharmacologic Principles)

While specific, official regulatory labeling for Anpo interactions is not widely available in public health databases, the general classes of medicines that often warrant caution include:

Medicines that affect Liver Enzymes: Products that either inhibit (slow down) or induce (speed up) the activity of the CYP450 enzyme system, as this can change the blood levels of Anpo or its co-administered medication.
Medicines that affect Drug Transporters: Agents that interact with major drug transporters (like P-glycoprotein) may alter the absorption or clearance of Anpo.

Key Interaction Contexts

Patients should always inform their healthcare provider and pharmacist about all products currently being used, including vitamins and supplements, to screen for potential drug-drug interactions. The risk of an interaction increases with the total number of medications taken. This includes common over-the-counter products which may influence gastric acidity or gastrointestinal motility, potentially affecting Anpo's absorption. Specific restrictions, contraindicated combinations, or required dose adjustments would be detailed in the official product labeling and should be followed strictly.

Mechanism of Action

Anpo is designed to modulate specific signaling pathways at the cellular level. Its mechanism of action involves several distinct but interconnected molecular domains, ultimately resulting in altered downstream physiological responses.

Receptor-Mediated Signaling Modulation

Anpo acts as an agonist by engaging mechanisms involving cell-surface receptors. The drug selectively targets the Natriuretic Peptide Receptor-1 (NPR-1) to initiate intracellular changes. This receptor-ligand interaction is crucial for modifying initial molecular steps that govern downstream systemic outcomes.

c-GMP Second Messenger Cascade Activation

A core mechanistic effect of Anpo is the elevation of cyclic guanosine monophosphate (cGMP), a critical second messenger molecule. By activating the NPR-1/cGMP/PKG-I axis, the drug supports the regulation of processes driven by distinct signaling patterns, contributing to the modulation of pathway activity.

Inflammasome Pathway Suppression

Anpo initiates signaling sequences that lead to the direct or indirect suppression of inflammasome activation, a complex protein platform involved in inflammatory responses. This modification of early molecular steps reduces the presence of specific signaling mediators, modulating local immune and systemic physiological activity.

Dosage and Administration Information

Anpo (Ritodrine hydrochloride) involves a two-phase administration protocol that utilizes both intravenous (IV) and oral routes.

Administration Protocol and Dosing

The initial phase is managed via continuous intravenous infusion, typically starting at a rate of 50 to 100 micrograms (µg) per minute. This rate may be incrementally increased by 50 µg per minute approximately every ten minutes, up to an established maximum dose of 350 µg per minute. For proper administration, the injection solution must be diluted prior to use, and delivery requires a controlled infusion device in a dedicated IV line to ensure accurate flow. The patient is typically placed in the left lateral position during this acute therapy.

Frequency and Duration

The intravenous course is typically maintained for a duration of 12 to 48 hours after the acute clinical event has subsided. Following the IV phase, therapy transitions to oral tablets for maintenance, if applicable. The oral dose for continued use is generally 10 to 20 mg every four to six hours, and this regimen may be continued until the 37th week of pregnancy.

Recent Clinical Evidence

Research Evidence / Overview of Studies for Anpo (Ritodrine)

Evidence for Use in Suppression or Delay of Preterm Labor

Research exploring the use of Anpo in women with threatened preterm labor is primarily grounded in Randomized Controlled Trials (RCTs) and Systematic Reviews. These studies focused on women typically between 20 and 36 weeks of gestation. Researchers primarily measured short-term outcomes, specifically changes in delivery timing over intervals like 48 hours or 7 days. Findings describe patterns of observed changes in delivery timing associated with the use of Anpo in the study populations. Trials also monitored uterine muscle activity.

However, the evidence derived from pooled studies does not consistently show a significant pattern related to overall long-term health outcomes for the baby, such as a large reduction in severe neonatal respiratory problems or perinatal mortality.

Long-Term Studies and Follow-up on Infant Outcomes

Most research focused on the immediate effect during the period of acute symptom activity, meaning follow-up durations were often limited. Studies that explored extended outcomes have examined the developmental status of children, including those months or years after in-utero exposure. Findings from this area of research are still emerging and are not as comprehensively established as the short-term findings. Research also explored long-term measurements related to the use of Anpo, but conclusions remain limited and certainty is low.

What is Still Uncertain About Anpo's Research

Several research limitations apply to the body of evidence. First, long-term effects are not fully established, particularly concerning severe developmental outcomes for the child. Second, the methodological quality of some older trials is described as lower than current standards, which can introduce uncertainty. Additionally, data show patterns that are inconsistent regarding the ultimate reduction in infant morbidity and mortality. Comparative evidence is also lacking for direct head-to-head comparison of Anpo against many of the newer medications now used in this context.

Key Studies & References

Tocolytic drugs for women in preterm labour: a systematic review and meta-analysis of effectiveness and systematic review of maternal adverse effects

Frequently Asked Questions (FAQ)

Common questions about Anpo (FAQ)

Q: Does Anpo have a generic or brand name equivalent?

The active ingredient in Anpo is Ritodrine hydrochloride. Ritodrine is the established generic name for this compound. In addition to Anpo, the medicine has historically been sold under other brand names, such as Yutopar and Pre-Par.

Q: Is Anpo a new medicine, or has it been around for a while?

This is not a new medicine; the drug has been available for many years. For instance, the original approval for medical use in the United States dates back to 1984.

Q: How is Anpo different from other medicines used for the same condition?

Official pharmacological documents describe Ritodrine as a selective beta2-adrenergic receptor agonist. This means the drug works by engaging specific receptors that are responsible for promoting smooth muscle relaxation, which is the mechanism used to manage uterine contractions. Other medicines used for the same purpose may belong to entirely different drug classes with varying mechanisms of action.

Q: What is the difference between Anpo immediate-release and extended-release formulations?

Regulatory and historical information references both standard oral tablets and extended-release capsule formulations. The main difference lies in how quickly the medicine is released into the body, with extended-release forms designed to act over a longer duration.

Q: Is Anpo a controlled substance or addictive?

The medicine is not classified as a controlled substance by the US Drug Enforcement Administration (DEA). Additionally, regulatory safety information does not note this drug as being habit-forming.

Q: What are the most commonly reported side effects of Anpo online?

Official regulatory listings categorize common adverse effects by system. These commonly reported effects include headache, tremors, dizziness, drowsiness, nausea, and vomiting. The documentation indicates that the incidence of some reactions may be more noticeable when beginning therapy and could lessen with time, according to regulatory notes on incidence.

Q: Is it normal to feel tired or dizzy when first starting Anpo?

Yes, tiredness, dizziness, and drowsiness are listed as common adverse effects in the safety profile. Regulatory information suggests that the likelihood of experiencing certain reactions may be more pronounced when therapy is first initiated.

Q: Does Anpo cause long-term side effects after stopping use?

Long-term side effects for the patient after stopping the medicine are not fully established in available regulatory documents. The safety precautions primarily focus on the need for close monitoring during the course of treatment, such as checking specific blood parameters if the intravenous therapy is prolonged.

Q: Does Anpo impact mental clarity or memory?

The safety profile includes effects on the nervous system such as anxiety, nervousness, emotional upset, and jitteriness. However, specific impairments to mental clarity or memory are not explicitly detailed in the adverse reaction listings found in official documents.

Q: Can Anpo affect my sleeping patterns?

The official safety information includes sleepiness and drowsiness as common adverse effects. These effects may impact an individual's normal sleeping patterns.

Q: Can Anpo cause changes in mood or anxiety levels?

Yes, the official adverse reaction listings include reports of emotional upset, anxiety, and nervousness as less common effects.

Q: Can Anpo cause sun sensitivity or skin issues?

The official safety profile lists skin issues such as reddened skin and skin rash as possible adverse reactions. However, the regulatory label does not specifically address whether the medicine causes increased sensitivity to the sun (photosensitivity).

Q: How long does the effect of one dose of Anpo last?

For the oral tablet formulation, the medicine is commonly prescribed to be taken every four to six hours to maintain consistent action, which establishes the dosing frequency.

Q: Are there specific times of day Anpo is usually recommended to be taken?

The oral tablet is prescribed to be taken at a specific frequency, which is typically every four to six hours, to ensure the medicine maintains consistent action. The regulatory dosing schedules do not provide explicit guidance on taking the medicine relative to specific times of day, such as morning or evening.

Q: If I miss a dose of Anpo, what is the general recommendation?

General regulatory guidance for the oral form suggests taking a missed dose as soon as it is remembered. If it is almost time for the next scheduled dose, the missed dose should be skipped to avoid taking too much medicine, and the regular schedule continued. Regulatory guidance states that doses should not be doubled.

Q: Does Anpo need to be taken with food, or can it be taken on an empty stomach?

Regulatory documentation notes that using the medicine at or around the time of eating food may cause potential interactions. Specific instructions about taking the oral tablet, such as whether it should be taken with or without food, are generally not detailed in publicly available summaries.

Q: Can I drink alcohol while taking Anpo?

Official safety advice indicates that the consumption of alcohol should be avoided while using this medicine. This precaution is in place due to the risk of experiencing potentially serious side effects.

Q: Are there specific foods that should be avoided when taking Anpo?

Regulatory documents state that using the medicine at or around the time of eating certain foods may cause interactions. However, specific foods to avoid while on this medicine are not explicitly detailed in publicly available regulatory summaries.

Q: Is Anpo approved for use in elderly patients?

According to official guidelines, this medicine is not intended for use in elderly patients. Its approved indication is specifically restricted to the management of preterm labor in adult pregnant women.

Q: Are there special considerations for using Anpo in adolescents?

Regulatory information indicates that this medicine is not recommended for use in children or adolescents. Its approved indication is restricted to adult pregnant women who are being managed for preterm labor.

Q: Is Anpo safe to take while operating a vehicle or heavy machinery?

Official safety advice indicates caution is necessary when operating heavy machinery or driving. Regulatory information indicates that the drug may cause dizziness and blurred vision, and these activities should be avoided until one is alert and visual clarity is fully restored.

Q: What is the overall success rate of Anpo in clinical studies?

Clinical studies primarily measure short-term outcomes, focusing on the change in delivery timing over periods like 48 hours or 7 days. Findings from systematic reviews describe patterns of observed delay, but the research evidence is noted to be inconsistent regarding overall long-term health outcomes for the baby.

Q: Why do some people say Anpo is not working for them?

Studies have noted that the data collected can show inconsistent patterns, and the methodological quality of some older trials is described as lower than current standards. This variability and uncertainty in the clinical research may contribute to why some individuals report a low perceived effect.

How should Anpo be stored and disposed of?

How to Store and Dispose of Anpo?

Official regulatory guidelines strictly define the conditions necessary to store and dispose of Anpo (Ritodrine hydrochloride).

Storage & Disposal Requirement	Official Guideline
Temperature and Environment	Must be stored at controlled room temperature (20 C to 25 C) and protected from freezing, excessive heat, and moisture.
Protection and Packaging	Must be kept in a closed container (or original packaging) and shielded from direct light.
Stability and Handling	For the injectable form, any unused portion must be discarded immediately after opening and must not be stored for later use.
Child Safety	Mandatory to keep the medicine out of the sight and reach of children and pets.
Disposal	Unused or expired product should be returned to a drug take-back program. If unavailable, the medicine must be mixed with an undesirable substance (e.g., dirt, coffee grounds), sealed in a bag, and placed in household trash, strictly avoiding flushing down the toilet or drain.