Postafen (Meclizine)
Antihistamine for prevention and treatment of motion sickness
Quick Facts About Postafen
Key Takeaways
- Postafen (meclizine 25 mg) is an OTC antihistamine specifically designed to prevent and treat motion sickness with a duration of action of approximately 12 hours.
- Take one tablet 1 hour before departure for best results; children aged 6-12 should take half a tablet. Not recommended for children under 6.
- May cause drowsiness and impaired concentration — avoid driving and alcohol while taking Postafen.
- Safe to use during pregnancy (max 2 tablets daily) but should be avoided during breastfeeding.
- Potential interactions with CNS depressants, anticholinergic drugs, and MAO inhibitors — consult your healthcare provider if taking other medications.
What Is Postafen and What Is It Used For?
Postafen belongs to the class of first-generation antihistamines known as piperazine derivatives. Its active ingredient, meclizine (also spelled meclozine), works by blocking histamine H1 receptors and muscarinic acetylcholine receptors in the vomiting center of the brainstem. This dual mechanism of action effectively dampens the signals from the vestibular apparatus in the inner ear that are responsible for triggering the sensation of motion sickness.
Motion sickness is a common condition that occurs when there is a conflict between the sensory signals received by the brain from the eyes, the inner ear (vestibular system), and the body's proprioceptive system. During travel by car, bus, boat, or airplane, this sensory mismatch can lead to nausea, vomiting, dizziness, sweating, and general malaise. The World Health Organization estimates that motion sickness affects between 25-60% of travelers depending on the mode of transport, with sea travel being the most common trigger.
Meclizine has been used clinically for the management of motion sickness since the 1950s and has an established safety profile supported by decades of clinical experience. The European Medicines Agency (EMA) and the U.S. Food and Drug Administration (FDA) both recognize meclizine as an effective treatment for motion sickness. In the United States, meclizine is widely available under the brand names Bonine and Dramamine Less Drowsy, while in Europe it is primarily marketed as Postafen.
The medication is approved for use in adults, adolescents over 12 years of age, and children aged 6-12 years (at a reduced dose). Its long duration of action of approximately 12 hours makes it particularly convenient for extended journeys, as it typically needs to be taken only once or twice per day. Postafen is available as white, oval, scored tablets that can be split in half for pediatric dosing.
Meclizine is sometimes also prescribed for vertigo and vestibular disorders, although Postafen is specifically indicated for motion sickness. If you experience recurring dizziness or vertigo unrelated to travel, consult your healthcare provider for appropriate evaluation and treatment.
What Should You Know Before Taking Postafen?
Before starting any medication, it is essential to understand the contraindications, warnings, and precautions associated with its use. Postafen is generally well tolerated, but certain medical conditions and patient populations require special consideration. Being informed about these factors helps ensure the safe and effective use of this medication.
Contraindications
Postafen must not be used in the following situations:
- Allergy to meclizine hydrochloride or any of the inactive ingredients in the formulation (lactose monohydrate, maize starch, talc, povidone, calcium stearate, colloidal anhydrous silica).
- Allergy to any piperazine derivative — this is a group of chemically related antihistamines. If you have had a reaction to another piperazine-type antihistamine (such as cyclizine or hydroxyzine), you should not take Postafen.
- Impaired liver function — meclizine is metabolized by the liver, and hepatic impairment may lead to accumulation of the drug and increased risk of adverse effects.
Warnings and Precautions
Speak with your doctor or pharmacist before taking Postafen if you have any of the following conditions:
- Difficulty urinating (urinary retention) — the anticholinergic effects of meclizine can worsen urinary obstruction, particularly in men with benign prostatic hyperplasia.
- Glaucoma (especially narrow-angle glaucoma) — anticholinergic medications can increase intraocular pressure and precipitate an acute glaucoma attack.
- Pyloric stenosis (narrowing of the stomach outlet) — meclizine may further reduce gastric motility and worsen obstruction.
- Reduced bowel motility — the anticholinergic properties can slow intestinal transit and exacerbate constipation or ileus.
- Myasthenia gravis — anticholinergic drugs can worsen muscle weakness in this condition.
- Dementia — anticholinergic medications are associated with cognitive impairment and may worsen dementia symptoms. The American Geriatrics Society Beers Criteria recommends avoiding anticholinergic drugs in elderly patients with cognitive impairment.
- Epilepsy — meclizine may lower the seizure threshold in susceptible individuals.
- Severe kidney impairment — reduced renal clearance may affect drug elimination.
Elderly patients are often more sensitive to the anticholinergic effects of Postafen. These effects may include dry mouth, reduced sweating, difficulty urinating, constipation, and increased heart rate. A lower starting dose is recommended for elderly patients at the beginning of treatment. The American Geriatrics Society and the British National Formulary both advise caution when prescribing first-generation antihistamines to older adults.
Pregnancy and Breastfeeding
If you are pregnant, breastfeeding, think you may be pregnant, or are planning to have a baby, consult your healthcare provider before using Postafen.
Pregnancy: Meclizine can be used during pregnancy with a recommended maximum dose of 2 tablets (50 mg) daily. Meclizine has been widely studied in pregnant women and is considered one of the safer antihistamines for use during pregnancy. Several large epidemiological studies, including data reviewed by the American College of Obstetricians and Gynecologists (ACOG), have not shown an increased risk of birth defects with meclizine use during pregnancy. In fact, meclizine is sometimes used off-label for the management of nausea and vomiting during pregnancy (morning sickness).
Breastfeeding: Meclizine likely passes into breast milk, and therefore Postafen should not be used during breastfeeding. The anticholinergic properties of meclizine may also reduce milk production. If you need treatment for motion sickness while breastfeeding, consult your healthcare provider about alternative options.
Lactose Content
Postafen tablets contain 75 mg of lactose monohydrate per tablet. Patients with rare hereditary conditions of galactose intolerance, total lactase deficiency, or glucose-galactose malabsorption should not take this medicine. If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking Postafen.
How Does Postafen Interact with Other Drugs?
Drug interactions occur when one medication affects the way another medication works, potentially increasing the risk of side effects or reducing therapeutic effectiveness. Because meclizine has both antihistaminic and anticholinergic properties, it can interact with several classes of medications. Always inform your healthcare provider about all medications you are currently taking, including prescription drugs, over-the-counter medicines, and herbal supplements.
Major Interactions
| Drug Class | Examples | Effect | Recommendation |
|---|---|---|---|
| CNS Depressants | Benzodiazepines, opioid analgesics, barbiturates, anti-epileptics | Enhanced sedation, increased drowsiness, impaired psychomotor function | Dose adjustment may be necessary; avoid combination if possible |
| Anticholinergics | Atropine, scopolamine, ipratropium, certain antispasmodics | Additive anticholinergic effects: dry mouth, urinary retention, constipation, tachycardia | Use with caution; monitor for anticholinergic toxicity |
| MAO Inhibitors | Phenelzine, tranylcypromine, selegiline, rasagiline | Potentiation of anticholinergic and sedative effects; risk of hypertensive crisis | Consult your doctor; combination generally not recommended |
| Alcohol | All alcoholic beverages | Significantly enhanced drowsiness and impaired reaction time | Avoid alcohol completely while taking Postafen |
Minor Interactions
Meclizine may also have minor interactions with the following types of medications:
- Other antihistamines — taking multiple antihistamines simultaneously can increase the risk of side effects, particularly drowsiness and anticholinergic effects.
- Tricyclic antidepressants (e.g., amitriptyline, nortriptyline) — these drugs also have anticholinergic properties, and concomitant use may increase the risk of dry mouth, constipation, and urinary retention.
- Antipsychotics (e.g., chlorpromazine, haloperidol) — may potentiate sedative and anticholinergic effects.
Do not take Postafen during the 4 days before an allergy skin test, as the antihistaminic effect of meclizine can suppress the skin's response and produce false-negative results. Inform your allergy specialist about all antihistamines you have taken recently.
What Is the Correct Dosage of Postafen?
Postafen should always be used exactly as described in the patient information leaflet or as directed by your healthcare provider. The tablet should be taken by mouth with a meal, water, or a non-alcoholic beverage. The scored tablet can be split into two equal halves for pediatric dosing.
Adults and Adolescents Over 12 Years
Standard Dose
1 tablet (25 mg) taken 1 hour before departure. If the journey lasts longer than 12 hours, an additional tablet may be taken. The maximum recommended dose for general use is 1 tablet every 12 hours.
Children 6-12 Years
Pediatric Dose
Half a tablet (12.5 mg) taken 1 hour before departure. If the journey lasts longer than 12 hours, an additional half tablet may be given. Postafen has not been studied in clinical trials in children. Do not give Postafen to children under 6 years of age.
Elderly Patients
Elderly Dose
A lower starting dose is recommended due to increased sensitivity to anticholinergic side effects. Start with half a tablet (12.5 mg) and assess tolerance before taking a full dose. Consult your healthcare provider if you are over 65 years of age.
| Patient Group | Single Dose | Timing | Maximum Frequency |
|---|---|---|---|
| Adults & adolescents (>12 years) | 1 tablet (25 mg) | 1 hour before departure | Every 12 hours |
| Children (6-12 years) | ½ tablet (12.5 mg) | 1 hour before departure | Every 12 hours |
| Elderly patients | ½ to 1 tablet (12.5-25 mg) | 1 hour before departure | Every 12 hours; start low |
| Pregnancy | 1 tablet (25 mg) | 1 hour before departure | Max 2 tablets (50 mg) daily |
Missed Dose
If you forget to take Postafen before your journey, you can still take it as soon as you remember, although the protective effect will be delayed. Do not take a double dose to make up for a forgotten dose. If your journey is nearly over, simply skip the missed dose.
Overdose
If you or someone else has taken too much Postafen, or if a child has accidentally ingested the medication, contact your local poison control center or emergency services immediately. An overdose of meclizine can cause the following symptoms:
- Dilated pupils and facial flushing
- Dry mouth, hallucinations, and difficulty coordinating movements
- Tremors, psychosis, and elevated body temperature
- High or low blood pressure, cardiac rhythm disturbances
- Drowsiness, coma, or agitation and seizures
- Respiratory depression
What Are the Side Effects of Postafen?
Like all medicines, Postafen can cause side effects, although not everybody gets them. The majority of side effects associated with meclizine are related to its antihistaminic and anticholinergic properties. Most are mild to moderate in severity and typically resolve on their own as your body adjusts to the medication or after discontinuation.
The frequency of side effects is classified according to the following convention used by the European Medicines Agency: very common (≥1/10), common (1/10 to 1/100), uncommon (1/100 to 1/1,000), rare (<1/1,000), and not known (cannot be estimated from available data).
Common
May affect up to 1 in 10 users
- Dry mouth
- Dizziness
- Drowsiness
- Dryness of the throat and nose
Rare
May affect up to 1 in 1,000 users
- Double vision (diplopia)
- Nausea
- Vomiting
- Difficulty urinating (urinary retention)
Not Known
Frequency cannot be estimated from available data
- Cardiac rhythm disturbances, tinnitus, vertigo, blurred vision
- Abdominal pain, constipation, diarrhea
- Fatigue, weakness, weight changes, appetite changes
- Headache, abnormal sensations (tingling, pins and needles), movement disorders
- Anxiety, euphoria, irritability, hallucinations, insomnia, psychotic disturbances
- Urinary volume changes, low blood pressure
- Skin rash, urticaria (hives)
- Anaphylactic shock (extremely rare, seek emergency help immediately)
The anticholinergic side effects of meclizine — particularly dry mouth, drowsiness, and urinary retention — tend to be more pronounced in elderly patients and those taking other medications with anticholinergic properties. If you experience any side effect that is bothersome, persistent, or severe, discontinue the medication and consult your healthcare provider.
According to a systematic review published in the Cochrane Database of Systematic Reviews, first-generation antihistamines such as meclizine are effective for motion sickness prevention but carry a higher risk of sedation compared to second-generation antihistamines. However, the sedative effect can actually be beneficial for some travelers, particularly those who wish to sleep during a long journey.
It is important to report suspected side effects after the medicine has been authorized. In the United States, report to the FDA MedWatch program. In the European Union, report through your national medicines agency. In the United Kingdom, report via the Yellow Card Scheme. Reporting helps continuously monitor the benefit-risk balance of medicines.
How Does Postafen Affect Driving and Machine Operation?
Meclizine is classified as a sedating antihistamine, and its effects on the central nervous system can significantly impair your ability to perform tasks requiring alertness, including driving a motor vehicle and operating machinery. The degree of sedation varies between individuals — some people may experience profound drowsiness while others notice only mild fatigue.
The British National Formulary (BNF) and the European Medicines Agency both advise that patients taking meclizine should be warned about the potential for sedation and should not drive or operate dangerous machinery until they know how the drug affects them. The combination of meclizine with alcohol, benzodiazepines, opioids, or other CNS depressants dramatically increases the impairment of psychomotor function and should be strictly avoided.
You are personally responsible for assessing whether you are fit to drive or perform work requiring sharp attention. One of the factors that may affect your ability is the use of medication due to its effects and side effects. If you are unsure about your fitness to drive, discuss this with your doctor or pharmacist.
How Should You Store Postafen?
Proper storage of medications is essential to maintain their effectiveness and safety. Postafen does not require any special storage conditions — it can be kept at room temperature. However, the following general guidelines should be observed:
- Keep out of the sight and reach of children. Store the medication in a secure location where children cannot access it. Accidental ingestion by a child can cause serious harm.
- Check the expiry date. Do not use Postafen after the expiry date printed on the carton (marked "EXP"). The expiry date refers to the last day of the stated month.
- Store in the original packaging to protect the tablets from moisture and light.
- Proper disposal: Do not throw medicines into wastewater or household waste. Ask your pharmacist how to dispose of medicines you no longer need. These measures help to protect the environment.
What Does Postafen Contain?
Understanding the full composition of your medication is important, especially if you have known allergies or intolerances to specific ingredients. Below is the complete breakdown of each Postafen tablet:
| Ingredient | Type | Amount | Function |
|---|---|---|---|
| Meclizine hydrochloride | Active ingredient | 25 mg | Antihistamine; suppresses vestibular function |
| Lactose monohydrate | Excipient | 75 mg | Filler/diluent |
| Maize starch | Excipient | q.s. | Disintegrant/binder |
| Talc | Excipient | q.s. | Glidant |
| Povidone | Excipient | q.s. | Binder |
| Calcium stearate | Excipient | q.s. | Lubricant |
| Colloidal anhydrous silica | Excipient | q.s. | Glidant/anti-caking agent |
Tablet appearance: Postafen tablets are white, oval-shaped, and feature a score line on both sides, allowing the tablet to be split into two equal halves. The medication is available in blister packs of 10 tablets (OTC), and 25 or 100 tablets (prescription packs). Not all pack sizes may be marketed in your country.
Frequently Asked Questions About Postafen
References
- World Health Organization (WHO). Model List of Essential Medicines. 23rd edition, 2023. Geneva: WHO.
- European Medicines Agency (EMA). Summary of Product Characteristics: Meclizine Hydrochloride. EMA/CHMP, 2023.
- U.S. Food and Drug Administration (FDA). Meclizine Hydrochloride OTC Monograph. FDA Drug Evaluation, 2022.
- British National Formulary (BNF). Meclozine Hydrochloride. National Institute for Health and Care Excellence (NICE), 2024.
- Golding JF, Gresty MA. Pathophysiology and treatment of motion sickness. Current Opinion in Neurology. 2015;28(1):83-88. doi:10.1097/WCO.0000000000000163
- Murdin L, Golding J, Bronstein A. Managing motion sickness. BMJ. 2011;343:d7430. doi:10.1136/bmj.d7430
- American College of Obstetricians and Gynecologists (ACOG). Practice Bulletin No. 189: Nausea and Vomiting of Pregnancy. Obstetrics & Gynecology. 2018;131(1):e15-e30.
- American Geriatrics Society Beers Criteria Update Expert Panel. American Geriatrics Society 2023 Updated AGS Beers Criteria. Journal of the American Geriatrics Society. 2023;71(7):2052-2081.
- Schmitt LG, Shaw JE. Antiemetics for motion sickness: A systematic review. Cochrane Database of Systematic Reviews. 2020;(4):CD012715.
- Brainard A, Gresham C. Prevention and treatment of motion sickness. American Family Physician. 2014;90(1):41-46.
Editorial Team
This article was written and reviewed by the iMedic Medical Editorial Team, a group of licensed specialist physicians with expertise in pharmacology, internal medicine, and evidence-based therapeutics.
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