Common uses of Periactin (cyproheptadine)
Periactin (cyproheptadine) is an older, first-generation H1 antihistamine with additional antiserotonergic activity. Clinically, it is used to relieve symptoms of allergic conditions such as allergic rhinitis, conjunctival itching, hives (urticaria), and generalized pruritus. Because it crosses the blood–brain barrier, it can be more sedating than newer non-drowsy antihistamines; in some cases, that sedation can be helpful for nighttime itching that disrupts sleep.
Beyond allergy relief, Periactin’s serotonin-blocking properties have made it a useful option in select headache disorders. It is commonly used off-label as migraine prophylaxis, especially in children and adolescents who may not tolerate other preventive medicines. Some clinicians also employ it for cluster headaches or for refractory cyclic vomiting syndrome when a serotonergic component is suspected.
Periactin’s tendency to increase appetite and promote weight gain has led to off-label use as an appetite stimulant in carefully selected patients—such as children with poor weight gain, older adults experiencing weight loss, or people with certain chronic conditions. This strategy should be undertaken only with medical oversight, because not everyone benefits, side effects are common, and addressing underlying causes of low appetite or weight loss is essential.
Periactin dosage and direction
Your exact Periactin dosing depends on age, indication, other medications, and how you tolerate side effects. For allergy symptoms in adults, clinicians commonly start with 4 mg taken two to three times daily, adjusting based on response and drowsiness; some patients do best with a larger portion at bedtime. Pediatric dosing is typically lower and based on age and weight; a clinician may start with small divided doses and titrate up cautiously. For headache prevention, doses are often initiated low and increased slowly to balance benefit with sedation.
Periactin may be taken with or without food. Because it can cause drowsiness and impair coordination, many patients prefer a first dose in the evening to gauge sensitivity before adding daytime doses. Do not exceed the maximum daily amount recommended by your prescriber. If daytime sedation interferes with school, work, or driving, speak with your clinician about dose timing, dose reduction, or an alternative therapy.
Never use Periactin for self-directed weight gain, bodybuilding, or cosmetic appetite enhancement. If appetite stimulation is part of a therapeutic plan, your clinician will individualize dosing, monitor weight, and reassess the need and duration regularly. Older adults and people with liver or kidney impairment often require lower starting doses and slower titration.
Precautions before and during Periactin use
Periactin can cause significant drowsiness, slower reaction time, dizziness, and blurred vision. Avoid driving, operating machinery, or engaging in tasks that require alertness until you know how it affects you. Alcohol, cannabis, sleep aids, benzodiazepines, opioids, and other sedatives can amplify impairment and should be avoided or used only under explicit medical guidance. In children, older adults, and people with cognitive impairment, the risk of confusion, falls, or paradoxical agitation warrants extra caution and close monitoring.
Anticholinergic effects—dry mouth, constipation, urinary retention, and increased intraocular pressure—are common. Use with caution if you have narrow-angle glaucoma, urinary retention, benign prostatic hyperplasia, bowel obstruction risk, or severe asthma. If you are pregnant, planning pregnancy, or breastfeeding, discuss risks and alternatives with your clinician; data are limited, and sedating antihistamines can affect infants and milk production. Tell your clinician about all medicines and supplements you take, as well as any history of liver disease, cardiovascular disease, or sleep apnea.
Contraindications to Periactin
Do not use Periactin if you are taking monoamine oxidase inhibitors (MAOIs) or have used an MAOI within the past 14 days. It is also contraindicated in newborn or premature infants, in patients with narrow-angle glaucoma, in those with urinary retention or bladder neck obstruction, in people with stenosing peptic ulcer or pyloroduodenal obstruction, and during an acute asthma attack. Many product labels advise against use while breastfeeding. If any of these apply to you, or if you are unsure, consult a clinician before considering Periactin.
Possible side effects of Periactin
Common side effects include drowsiness, fatigue, dizziness, dry mouth, dry eyes, blurred vision, constipation, and increased appetite with potential weight gain. Some people experience headache, nausea, or mild confusion at initiation that may improve as the body adjusts. If daytime sedation is problematic, a clinician may adjust timing or dose, or recommend a less sedating alternative.
Less common but important effects include difficulty urinating, palpitations, low blood pressure, agitation (especially in some children), tremor, photosensitivity, and, rarely, liver enzyme elevations or jaundice. Seek urgent care for severe confusion, fainting, hallucinations, rapid or irregular heartbeat, severe allergic reaction (rash, swelling, trouble breathing), or signs of an anticholinergic crisis (very hot, flushed skin; dilated pupils; severe agitation). Report persistent or bothersome effects to your clinician; dose adjustments or a different medication may be appropriate.
Periactin drug interactions
Sedation and cognitive impairment can be intensified when Periactin is combined with alcohol, benzodiazepines, opioids, barbiturates, gabapentinoids, muscle relaxants, sleep medications, some anti-seizure drugs, or cannabinoids. Combining with other anticholinergic agents (for example, certain bladder medications, tricyclic antidepressants, some antipsychotics, or motion sickness patches) can increase risks of constipation, urinary retention, dry mouth, confusion, and overheating, especially in older adults.
MAOIs are contraindicated with Periactin. Because Periactin antagonizes serotonin, it may blunt the therapeutic effect of serotonergic antidepressants (such as SSRIs) and is sometimes used medically to treat serotonin syndrome—highlighting the need for careful coordination of care. Always provide a complete medication and supplement list to your clinician and pharmacist, including over-the-counter antihistamines and herbal products that may cause drowsiness or anticholinergic effects.
Missed dose
If you miss a dose, take it when you remember unless it is close to the time of your next dose. If it is nearly time for the next scheduled dose, skip the missed dose and resume your regular schedule. Do not double up to “catch up,” as this can increase side effects such as sedation or anticholinergic symptoms. If you frequently forget doses, ask your clinician about simplified dosing schedules or reminders.
Overdose
Overdose may cause pronounced drowsiness or agitation, confusion, hallucinations, dilated pupils, flushed hot skin, dry mouth, rapid heartbeat, tremor, seizures, and, in severe cases, coma or heart rhythm changes. This is a medical emergency—call 911 and/or contact Poison Control at 1-800-222-1222 in the U.S. Do not induce vomiting unless instructed by medical professionals. Supportive hospital care is often required, particularly for children, who are more vulnerable to serious anticholinergic toxicity.
Storage
Store Periactin tablets at room temperature (generally 20–25°C/68–77°F), protected from excess heat, moisture, and light. Keep the bottle tightly closed and use a child-resistant cap. Do not store in a bathroom. Keep out of reach of children and pets. Safely discard expired or unused medication—your pharmacist or local take-back program can advise on disposal.
U.S. sale and prescription policy
In the United States, Periactin (cyproheptadine) is a prescription-only medication. You cannot legally buy Periactin without prescription from a licensed clinician. Be wary of websites or marketplaces offering it “no Rx” or “overnight” without a doctor’s review; these are often illegal pharmacies that may ship counterfeit or unsafe products. For consumer safety, the FDA’s BeSafeRx initiative and the National Association of Boards of Pharmacy help you identify legitimate pharmacies and telehealth services that require appropriate medical evaluation.
If you are seeking convenient access, consider legitimate pathways: schedule an in-person visit, use an established telehealth platform, or work with integrated health systems that offer coordinated care and in-network pharmacies. For example, large regional systems like Geisinger provide structured virtual and in-person evaluations and can dispense medications through their pharmacies once a clinician determines Periactin is appropriate. These services do not bypass prescriptions; rather, they streamline the legal process of evaluation, prescribing, and dispensing to keep you safe and compliant with U.S. law.
