Acyclovir 800mg 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 1982
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 or shingles. It works by stopping the virus from growing and spreading in your body. It does not cure these infections but helps to reduce symptoms and shorten their duration.
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. If it causes stomach upset, taking it with food may help.
If you're using this medication to treat cold sores, chickenpox, shingles, or genital herpes, start taking it as soon as your symptoms appear. The sooner you start, the more effective it will be. Don't delay taking your medication, as it may not work as well if you start too late.
Continue taking your medication exactly as directed by your doctor or healthcare provider, even if you start to feel better.
Storing and Disposing of Your Medication
To keep your medication effective and safe, store it at room temperature, away from light and moisture. Avoid storing it in a bathroom. Keep all medications in a secure location, out of the reach of children and pets.
When your medication is no longer needed or has expired, dispose of it properly. Do not flush it down the toilet or pour it down the drain unless instructed to do so. If you're unsure about the best way to dispose of your medication, consult your pharmacist. You may also have access to a drug take-back program in your area.
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 continue with your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for a 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. If it causes stomach upset, taking it with food may help.
If you're using this medication to treat cold sores, chickenpox, shingles, or genital herpes, start taking it as soon as your symptoms appear. The sooner you start, the more effective it will be. Don't delay taking your medication, as it may not work as well if you start too late.
Continue taking your medication exactly as directed by your doctor or healthcare provider, even if you start to feel better.
Storing and Disposing of Your Medication
To keep your medication effective and safe, store it at room temperature, away from light and moisture. Avoid storing it in a bathroom. Keep all medications in a secure location, out of the reach of children and pets.
When your medication is no longer needed or has expired, dispose of it properly. Do not flush it down the toilet or pour it down the drain unless instructed to do so. If you're unsure about the best way to dispose of your medication, consult your pharmacist. You may also have access to a drug take-back program in your area.
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 continue with your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for a missed one.
Lifestyle & Tips
- Drink plenty of fluids while taking this medication to help prevent kidney problems.
- Complete the full course of medication as prescribed, even if symptoms improve.
- Acyclovir does not prevent the spread of herpes viruses to others. Avoid sexual contact or other close contact with others when lesions are present.
- For genital herpes, use barrier methods (condoms) even when asymptomatic 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. For Herpes Zoster: 800 mg orally 5 times a day for 7 to 10 days. For Recurrent Genital Herpes (episodic treatment): 800 mg orally twice daily for 5 days OR 800 mg orally three times daily for 2 days.
Dose Range:
200 - 800 mg
Condition-Specific Dosing:
Herpes Zoster (Shingles):
800 mg orally 5 times a day for 7 to 10 days
Varicella (Chickenpox):
800 mg orally 4 times a day for 5 days
Genital Herpes (initial episode):
200 mg orally 5 times a day for 10 days OR 400 mg orally 3 times a day for 7-10 days
Genital Herpes (recurrent, episodic):
800 mg orally twice daily for 5 days OR 800 mg orally three times daily for 2 days
Genital Herpes (suppression):
400 mg orally twice daily
Pediatric Dosing
Neonatal:
Not established for oral formulation; IV dosing used for HSV.
Infant:
Not established for oral formulation; IV dosing used for HSV.
Child:
Varicella (2 years and older): 20 mg/kg (up to 800 mg) orally 4 times a day for 5 days. HSV (immunocompromised): Dosing varies, often 20 mg/kg (up to 800 mg) 3-4 times a day.
Adolescent:
Dosing generally follows adult guidelines for specific indications (e.g., herpes zoster, genital herpes).
Dose Adjustments
Renal Impairment:
Mild:
CrCl 25-50 mL/min: Dose q8h or q12h depending on indication.
Moderate:
CrCl 10-25 mL/min: Dose q12h or q24h depending on indication.
Severe:
CrCl <10 mL/min: Dose q24h. For Herpes Zoster: 800 mg once daily. For Recurrent Genital Herpes (episodic): 400 mg once daily.
Dialysis:
Hemodialysis: Administer dose after dialysis session. Peritoneal Dialysis: No supplemental dose needed after dialysis.
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 monophosphate by viral thymidine kinase, then to acyclovir triphosphate by cellular enzymes. Acyclovir triphosphate inhibits viral DNA synthesis and replication by competing with deoxyguanosine triphosphate for incorporation into viral DNA, leading to chain termination.
Pharmacokinetics
Absorption:
Bioavailability:
10-20% (oral)
Tmax:
1.5-2 hours
FoodEffect:
Food does not significantly affect absorption.
Distribution:
Vd:
0.8 L/kg
ProteinBinding:
9-33%
CnssPenetration:
Yes (approximately 50% of plasma concentrations)
Elimination:
HalfLife:
2.5-3.3 hours (normal renal function)
Clearance:
Not available (primarily renal excretion)
ExcretionRoute:
Renal (glomerular filtration and tubular secretion)
Unchanged:
62-91%
Pharmacodynamics
OnsetOfAction:
Varies by indication and viral load; antiviral effect begins with first dose.
PeakEffect:
Not directly quantifiable for antiviral effect; peak plasma concentrations reached in 1.5-2 hours.
DurationOfAction:
Plasma half-life is 2.5-3.3 hours, but intracellular triphosphate has a longer half-life (up to 12 hours), allowing for less frequent dosing.
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Attention Immediately
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 help right away:
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
Life-threatening blood problems, 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 help:
Upset stomach or vomiting
Feeling tired or weak
Reporting Side Effects
This is not an exhaustive list of possible 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 help right away:
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
Life-threatening blood problems, 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 help:
Upset stomach or vomiting
Feeling tired or weak
Reporting Side Effects
This is not an exhaustive list of possible 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., urinating less than usual, swelling in your feet or ankles)
- Signs of neurological problems (e.g., confusion, hallucinations, unusual behavior, seizures, difficulty speaking, tremors)
- Severe dizziness or drowsiness
- Easy bruising or bleeding
- Severe skin rash or blistering
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 it is safe to take this medication 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 it is safe to take this medication 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 liquids 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 options and implications.
If you have genital herpes, note 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 exhibit any symptoms. To minimize the risk of transmission, use a latex or polyurethane condom during sexual activity and consult your doctor for 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 liquids 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 options and implications.
If you have genital herpes, note 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 exhibit any symptoms. To minimize the risk of transmission, use a latex or polyurethane condom during sexual activity and consult your doctor for guidance.
Overdose Information
Overdose Symptoms:
- Nausea
- Vomiting
- Diarrhea
- Headache
- Confusion
- Hallucinations
- Seizures
- Kidney failure (elevated BUN and serum creatinine)
What to Do:
Seek immediate medical attention or call a poison control center (1-800-222-1222). Hemodialysis can remove acyclovir from the blood.
Drug Interactions
Major Interactions
- Foscarnet (increased risk of renal toxicity)
- Mycophenolate Mofetil (increased concentrations of both drugs)
Moderate Interactions
- Probenecid (decreases renal clearance of acyclovir, increasing plasma levels)
- Tenofovir (increased risk of renal toxicity)
- Zidovudine (may cause drowsiness/lethargy)
Monitoring
Baseline Monitoring
Renal function (BUN, serum creatinine)
Rationale: Acyclovir is primarily renally eliminated; dose adjustments are necessary in renal impairment to prevent accumulation and toxicity.
Timing: Prior to initiation of therapy, especially in elderly patients or those with known renal dysfunction.
Routine Monitoring
Hydration status
Frequency: Daily during therapy, especially with high doses or in patients at risk for dehydration.
Target: Adequate fluid intake to prevent renal crystallization.
Action Threshold: Signs of dehydration or decreased urine output warrant immediate intervention.
Renal function (BUN, serum creatinine)
Frequency: Periodically during prolonged therapy or in patients with pre-existing renal impairment, or if signs of renal dysfunction develop.
Target: Within patient's baseline or normal limits.
Action Threshold: Significant increase in BUN/creatinine warrants dose adjustment or discontinuation.
Symptom Monitoring
- Signs of renal dysfunction (e.g., decreased urine output, swelling)
- Neurological symptoms (e.g., confusion, hallucinations, seizures, tremors, lethargy) - especially in elderly or renally impaired patients
- Gastrointestinal upset (nausea, vomiting, diarrhea)
- Skin rash or itching
Special Patient Groups
Pregnancy
Category B. Studies in animals have shown no evidence of harm to the fetus. Human data from the Acyclovir Pregnancy Registry did not show an increased risk of birth defects. Use only if clearly needed and potential benefits outweigh potential risks.
Trimester-Specific Risks:
First Trimester:
No increased risk of birth defects observed in human data.
Second Trimester:
No specific increased risk identified.
Third Trimester:
No specific increased risk identified.
Lactation
L2 (Likely Compatible). Acyclovir is excreted into breast milk. Infant exposure is low, and adverse effects in breastfed infants are not expected. Monitor infant for diarrhea or rash.
Infant Risk:
Low risk
Pediatric Use
Dosing is weight-based for varicella in children 2 years and older. Safety and efficacy for other indications in younger children are less established for oral formulations. Close monitoring for adverse effects is important.
Geriatric Use
Elderly patients are at increased risk for acyclovir-induced neurotoxicity and renal dysfunction due to age-related decline in renal function. Dose adjustments based on creatinine clearance are crucial. Maintain adequate hydration.
Clinical Information
Clinical Pearls
- Acyclovir is most effective when initiated at the earliest sign or symptom of a viral infection (e.g., within 24-72 hours of rash onset for shingles/chickenpox, or at first prodromal symptoms for herpes simplex).
- Adequate hydration is critical during acyclovir therapy, especially with high doses or in patients with pre-existing renal impairment, to prevent renal tubular crystallization.
- Acyclovir does not eradicate latent herpes virus from the body and does not prevent recurrence or transmission.
- Resistance to acyclovir can develop, particularly in immunocompromised patients with prolonged or repeated exposure.
- Neurological adverse effects (e.g., confusion, hallucinations, seizures) are rare but more common in elderly patients or those with renal impairment; prompt recognition and dose adjustment are necessary.
Alternative Therapies
- Valacyclovir (prodrug of acyclovir, better bioavailability, less frequent dosing)
- Famciclovir (prodrug of penciclovir, similar spectrum, less frequent dosing)
Cost & Coverage
Average Cost:
$30 - $100 per 30 tablets
Generic Available:
Yes
Insurance Coverage:
Tier 1 or 2 (Generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about your medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.