Acyclovir 400mg Tablets
It is used to treat shingles or certain other herpes infections.It is used to treat chickenpox.It may be given to you for other reasons. Talk with the doctor.
Drug Class
Antiviral
Pharmacologic Class
Synthetic nucleoside analog
Pregnancy Category
Category B
FDA Approved
Jan 1984
DEA Schedule
Not Controlled
Overview
What is this medicine?
Acyclovir is an antiviral medicine used to treat infections caused by certain viruses, such as herpes (cold sores, genital herpes) and chickenpox/shingles. It works by stopping the virus from growing and spreading in your body.
How to Use This Medicine
Taking Your Medication
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely. You can take this medication with or without food, but if it causes stomach upset, take it with food to help minimize this side effect.
If you're taking this medication to treat cold sores, chickenpox, shingles, or genital herpes, start taking it as soon as symptoms appear. The sooner you start treatment, the more effective it will be. Don't delay, as taking it too late may reduce its effectiveness.
Continue taking your medication as directed by your doctor or healthcare provider, even if you start feeling better. It's essential to complete the full treatment course to ensure the best possible outcome.
Storing and Disposing of Your Medication
To maintain the quality and safety of your medication, store it at room temperature, away from light and moisture. Keep it in a dry place, avoiding storage in a bathroom. Make sure to keep all medications out of the reach of children and pets to prevent accidental ingestion.
When disposing of unused or expired medication, do not flush it down the toilet or pour it down the drain unless specifically instructed to do so. Instead, check with your pharmacist for guidance on the best disposal method. You may also want to explore local drug take-back programs for a safe and environmentally responsible way to dispose of your medication.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely. You can take this medication with or without food, but if it causes stomach upset, take it with food to help minimize this side effect.
If you're taking this medication to treat cold sores, chickenpox, shingles, or genital herpes, start taking it as soon as symptoms appear. The sooner you start treatment, the more effective it will be. Don't delay, as taking it too late may reduce its effectiveness.
Continue taking your medication as directed by your doctor or healthcare provider, even if you start feeling better. It's essential to complete the full treatment course to ensure the best possible outcome.
Storing and Disposing of Your Medication
To maintain the quality and safety of your medication, store it at room temperature, away from light and moisture. Keep it in a dry place, avoiding storage in a bathroom. Make sure to keep all medications out of the reach of children and pets to prevent accidental ingestion.
When disposing of unused or expired medication, do not flush it down the toilet or pour it down the drain unless specifically instructed to do so. Instead, check with your pharmacist for guidance on the best disposal method. You may also want to explore local drug take-back programs for a safe and environmentally responsible way to dispose of your medication.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Drink plenty of fluids while taking this medication to help prevent kidney problems.
- Acyclovir does not cure herpes infections, but it can help reduce the severity and frequency of outbreaks.
- Even with treatment, you can still spread herpes viruses to others. Avoid sexual contact during outbreaks and use barrier methods (like condoms) to reduce transmission risk.
Available Forms & Alternatives
Available Strengths:
- Acyclovir 200mg/5ml Oral Susp
- Acyclovir 200mg Capsules
- Acyclovir 400mg Tablets
- Acyclovir 800mg Tablets
- Acyclovir Sodium 50mg/ml Inj, 20ml
- Acyclovir 800mg Tablets
- Acyclovir 5% Ointment 15gm
- Acyclovir 5% Ointment 30gm
- Acyclovir Sodium 50mg/ml Inj, 10ml
- Acyclovir 5% Ointment 2x5gm
- Acyclovir 5% Ointment 15gm
- Acyclovir 200mg Capsules
- Acyclovir 5% Ointment 30gm
- Acyclovir 5% Ointment 5gm
- Acyclovir 5% Cream 5gm
- Acyclovir 5% Cream 5gm
Dosing & Administration
Adult Dosing
Standard Dose:
Varies by indication. E.g., Genital Herpes (initial): 200mg 5 times daily for 10 days; Genital Herpes (suppression): 400mg twice daily; Herpes Zoster: 800mg 5 times daily for 7-10 days; Varicella: 800mg 4 times daily for 5 days.
Dose Range:
200 - 800 mg
Condition-Specific Dosing:
Genital Herpes (initial episode):
200 mg orally 5 times daily for 10 days, or 400 mg orally 3 times daily for 7-10 days.
Genital Herpes (chronic suppression):
400 mg orally twice daily, or 200 mg orally 3-5 times daily.
Herpes Labialis (cold sores):
200 mg orally 5 times daily for 5 days, or 400 mg orally 3 times daily for 5 days.
Herpes Zoster (shingles):
800 mg orally 5 times daily for 7 to 10 days.
Varicella (chickenpox):
800 mg orally 4 times daily for 5 days.
Pediatric Dosing
Neonatal:
Not established for oral formulation; IV acyclovir is used for neonatal herpes.
Infant:
Not established for oral formulation; IV acyclovir is used for infants.
Child:
Varicella (2 years and older): 20 mg/kg orally (max 800 mg) 4 times daily for 5 days. Herpes Simplex (immunocompromised): 20 mg/kg orally (max 800 mg) 3-4 times daily.
Adolescent:
Dosing generally follows adult recommendations for specific indications.
Dose Adjustments
Renal Impairment:
Mild:
CrCl 25-50 mL/min: Dose every 8 hours (e.g., for 800mg 5x/day, reduce to 800mg 3x/day).
Moderate:
CrCl 10-25 mL/min: Dose every 12 hours (e.g., for 800mg 5x/day, reduce to 800mg 2x/day).
Severe:
CrCl <10 mL/min: Dose every 24 hours (e.g., for 800mg 5x/day, reduce to 800mg 1x/day).
Dialysis:
Administer dose after hemodialysis. For CrCl <10 mL/min, dose every 24 hours. For hemodialysis, an additional dose should be administered after each dialysis session.
Hepatic Impairment:
Mild:
No adjustment needed.
Moderate:
No adjustment needed.
Severe:
No adjustment needed.
Pharmacology
Mechanism of Action
Acyclovir is a synthetic purine nucleoside analog with in vitro and in vivo inhibitory activity against herpes simplex virus types 1 (HSV-1), 2 (HSV-2), and varicella-zoster virus (VZV). It is converted to acyclovir triphosphate, an active form, by viral thymidine kinase. Acyclovir triphosphate inhibits viral DNA replication by competing with deoxyguanosine triphosphate for incorporation into viral DNA, leading to chain termination and irreversible inactivation of viral DNA polymerase.
Pharmacokinetics
Absorption:
Bioavailability:
10-20% (oral), decreases with increasing dose.
Tmax:
1.5-2.5 hours.
FoodEffect:
Food does not significantly affect the extent of absorption.
Distribution:
Vd:
0.8 L/kg (adults).
ProteinBinding:
9-33%.
CnssPenetration:
Limited (CSF concentrations are approximately 50% of plasma concentrations).
Elimination:
HalfLife:
2.5-3.3 hours (normal renal function); significantly prolonged in renal impairment.
Clearance:
Primarily renal via glomerular filtration and tubular secretion.
ExcretionRoute:
Renal (urine).
Unchanged:
62-91%.
Pharmacodynamics
OnsetOfAction:
Varies by indication and viral replication rate; clinical improvement typically seen within 2-3 days for acute infections.
PeakEffect:
Peak plasma concentrations reached within 1.5-2.5 hours.
DurationOfAction:
Related to dosing frequency and half-life; requires frequent dosing due to short half-life.
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention immediately:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Behavioral problems
Mood changes
Feeling confused
Hallucinations (seeing or hearing things that are not there)
Seizures
Shakiness
Feeling dizzy or sleepy
Abnormal burning, numbness, or tingling sensations
Changes in speech
Severe kidney problems, which may be indicated by:
+ Inability to pass urine
+ Blood in the urine
+ Changes in the amount of urine passed
+ Unexpected weight gain
Potentially life-threatening blood disorders, such as thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS), which may be indicated by:
+ Feeling extremely tired or weak
+ Bruising or bleeding
+ Dark urine or yellow skin and eyes
+ Pale skin
+ Changes in the amount of urine passed
+ Changes in eyesight
+ Weakness or numbness on one side of the body
+ Trouble speaking or thinking
+ Changes in balance
+ Fever
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other unusual symptoms, contact your doctor or seek medical attention:
Upset stomach or vomiting
Feeling tired or weak
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention immediately:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Behavioral problems
Mood changes
Feeling confused
Hallucinations (seeing or hearing things that are not there)
Seizures
Shakiness
Feeling dizzy or sleepy
Abnormal burning, numbness, or tingling sensations
Changes in speech
Severe kidney problems, which may be indicated by:
+ Inability to pass urine
+ Blood in the urine
+ Changes in the amount of urine passed
+ Unexpected weight gain
Potentially life-threatening blood disorders, such as thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS), which may be indicated by:
+ Feeling extremely tired or weak
+ Bruising or bleeding
+ Dark urine or yellow skin and eyes
+ Pale skin
+ Changes in the amount of urine passed
+ Changes in eyesight
+ Weakness or numbness on one side of the body
+ Trouble speaking or thinking
+ Changes in balance
+ Fever
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other unusual symptoms, contact your doctor or seek medical attention:
Upset stomach or vomiting
Feeling tired or weak
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Signs of kidney problems (e.g., changes in urination, swelling in feet or ankles)
- Severe dizziness or drowsiness
- Confusion, hallucinations, or unusual behavior
- Seizures
- Severe skin rash or blistering
- Easy bruising or bleeding
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced as a result of the allergy.
All medications you are currently taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins. This information will help your doctor and pharmacist assess potential interactions between this medication and other substances you are taking.
* Any existing health problems, as this medication may interact with certain conditions.
To ensure your safety, it is crucial to verify that this medication can be taken with all your current medications and health conditions. Never start, stop, or adjust the dose of any medication without first consulting your doctor.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced as a result of the allergy.
All medications you are currently taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins. This information will help your doctor and pharmacist assess potential interactions between this medication and other substances you are taking.
* Any existing health problems, as this medication may interact with certain conditions.
To ensure your safety, it is crucial to verify that this medication can be taken with all your current medications and health conditions. Never start, stop, or adjust the dose of any medication without first consulting your doctor.
Precautions & Cautions
Important Warnings and Precautions
When taking this medication, it is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are using this drug.
To stay hydrated, drink plenty of non-caffeinated fluids every day, unless your doctor advises you to limit your fluid intake.
If you are 65 years or older, use this medication with caution, as you may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or breastfeeding, consult your doctor to discuss the potential benefits and risks to you and your baby.
Herpes Infection Considerations
This medication is not a cure for herpes infections. Consult your doctor to understand the treatment and management of herpes.
If you have genital herpes, be aware that this medication will not prevent the spread of the infection. Avoid any sexual activity when you have active sores or symptoms of genital herpes. Additionally, genital herpes can still be transmitted even when you do not have visible symptoms. To minimize the risk of transmission, use a latex or polyurethane condom during sexual activity and consult your doctor for further guidance.
When taking this medication, it is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are using this drug.
To stay hydrated, drink plenty of non-caffeinated fluids every day, unless your doctor advises you to limit your fluid intake.
If you are 65 years or older, use this medication with caution, as you may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or breastfeeding, consult your doctor to discuss the potential benefits and risks to you and your baby.
Herpes Infection Considerations
This medication is not a cure for herpes infections. Consult your doctor to understand the treatment and management of herpes.
If you have genital herpes, be aware that this medication will not prevent the spread of the infection. Avoid any sexual activity when you have active sores or symptoms of genital herpes. Additionally, genital herpes can still be transmitted even when you do not have visible symptoms. To minimize the risk of transmission, use a latex or polyurethane condom during sexual activity and consult your doctor for further guidance.
Overdose Information
Overdose Symptoms:
- Increased BUN and serum creatinine (indicating renal dysfunction)
- Neurological symptoms (e.g., confusion, hallucinations, seizures, coma)
- Nausea
- Vomiting
What to Do:
Supportive care. Hemodialysis can significantly remove acyclovir from the blood. Call 1-800-222-1222 (Poison Control).
Drug Interactions
Major Interactions
- Foscarnet (increased risk of renal toxicity)
- Mycophenolate mofetil (increased acyclovir and mycophenolate levels)
Moderate Interactions
- Probenecid (increases acyclovir AUC and decreases renal clearance)
- Tenofovir (increased risk of renal toxicity)
- Zidovudine (may cause severe drowsiness and lethargy)
- Other nephrotoxic drugs (e.g., NSAIDs, aminoglycosides, cyclosporine, tacrolimus - increased risk of renal dysfunction)
Monitoring
Baseline Monitoring
Renal function (BUN, serum creatinine, eGFR)
Rationale: Acyclovir is primarily renally eliminated, and dose adjustments are necessary in renal impairment.
Timing: Prior to initiation of therapy, especially in elderly patients or those with pre-existing renal conditions.
Hydration status
Rationale: Adequate hydration is important to prevent renal tubular crystallization, especially with IV acyclovir, but also relevant for high oral doses.
Timing: Prior to initiation.
Routine Monitoring
Renal function (BUN, serum creatinine, eGFR)
Frequency: Periodically during prolonged therapy, or more frequently in patients with renal impairment or those receiving concomitant nephrotoxic drugs.
Target: Within patient's baseline or normal limits.
Action Threshold: Significant increase in creatinine or BUN warrants dose adjustment or discontinuation.
Signs and symptoms of adverse effects (e.g., CNS, GI, renal)
Frequency: Daily, especially during initial therapy.
Target: Absence of severe or persistent symptoms.
Action Threshold: Development of severe headache, confusion, hallucinations, nausea, vomiting, or signs of renal dysfunction.
Symptom Monitoring
- Nausea
- Vomiting
- Diarrhea
- Headache
- Dizziness
- Fatigue
- Rash
- Confusion
- Hallucinations
- Seizures (rare)
- Signs of kidney problems (e.g., decreased urination, swelling in ankles/feet)
Special Patient Groups
Pregnancy
Category B. Studies in pregnant women have not shown an increased risk of birth defects. Acyclovir is generally considered safe for use during pregnancy when clinically indicated, especially for severe or recurrent herpes infections.
Trimester-Specific Risks:
First Trimester:
No increased risk of birth defects observed in human studies.
Second Trimester:
No increased risk of birth defects observed in human studies.
Third Trimester:
No increased risk of birth defects observed in human studies. May be used to prevent maternal outbreaks near term to reduce risk of neonatal herpes.
Lactation
Acyclovir is excreted into breast milk. However, the amount transferred to the infant is generally low, and adverse effects in breastfed infants are not expected. Considered compatible with breastfeeding (Lactation Risk Category L2).
Infant Risk:
Low risk of adverse effects.
Pediatric Use
Dosing is weight-based for children, especially for varicella. Safety and efficacy in children under 2 years for most indications are not well-established for oral formulations. IV acyclovir is used for severe infections in neonates and infants.
Geriatric Use
Elderly patients are more likely to have decreased renal function, which can lead to higher acyclovir concentrations and increased risk of adverse effects (especially CNS effects). Renal function should be monitored, and dose adjustments made accordingly. Adequate hydration is crucial.
Clinical Information
Clinical Pearls
- Acyclovir's oral bioavailability is low and variable, which is why higher doses are often needed for systemic infections compared to topical or IV forms.
- Adequate hydration is critical, especially with high doses or in patients with impaired renal function, to prevent renal tubular crystallization.
- Acyclovir does not eradicate the latent virus; it only suppresses viral replication during active infection.
- Early initiation of therapy (within 24-72 hours of symptom onset) is crucial for optimal efficacy in herpes zoster and varicella.
- Resistance to acyclovir can occur, particularly in immunocompromised patients with prolonged or repeated exposure.
Alternative Therapies
- Valacyclovir (prodrug of acyclovir with better bioavailability, allowing less frequent dosing)
- Famciclovir (prodrug of penciclovir, another antiviral with similar indications)
- Ganciclovir (for CMV, not typically HSV/VZV)
- Foscarnet (for resistant HSV/VZV, or in immunocompromised patients)
Cost & Coverage
Average Cost:
$10 - $50 per 30 tablets (400mg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 or 2 (Generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe and effective treatment, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it is a good idea to consult with your pharmacist. If you have any questions or concerns about this medication, do not hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When reporting the incident, be prepared to provide detailed information, including the name of the medication taken, the quantity, and the time it occurred.