Zovirax 200mg Capsules
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 herpes viruses, such as cold sores, genital herpes, and shingles (herpes zoster), and chickenpox. It works by stopping the virus from growing and spreading in the body.
How to Use This Medicine
Taking Your Medication Correctly
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 discomfort.
If you are taking this medication to treat cold sores, chickenpox, shingles, or genital herpes, it's essential to 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. This will help ensure that the infection is fully treated and reduce the risk of complications.
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, such as a closet or drawer, and avoid storing it in the 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 instructed to do so by your pharmacist or healthcare provider. Instead, check with your pharmacist for guidance on the best way to dispose of your medication. You may also want to explore local drug take-back programs in your area.
What to Do If You Miss 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 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 discomfort.
If you are taking this medication to treat cold sores, chickenpox, shingles, or genital herpes, it's essential to 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. This will help ensure that the infection is fully treated and reduce the risk of complications.
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, such as a closet or drawer, and avoid storing it in the 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 instructed to do so by your pharmacist or healthcare provider. Instead, check with your pharmacist for guidance on the best way to dispose of your medication. You may also want to explore local drug take-back programs in your area.
What to Do If You Miss 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 the missed one.
Lifestyle & Tips
- Drink plenty of fluids while taking this medication to help prevent kidney problems.
- Acyclovir does not cure herpes infections and does not prevent the spread of herpes to others. Avoid sexual contact during outbreaks.
- Take the medication exactly as prescribed, even if symptoms improve. Do not skip doses.
Available Forms & Alternatives
Available Strengths:
Generic Alternatives:
Dosing & Administration
Adult Dosing
Standard Dose:
Varies by indication. For genital herpes initial episode: 200 mg orally 5 times a day for 10 days. For chronic suppressive therapy: 400 mg orally twice daily.
Dose Range:
200 - 800 mg
Condition-Specific Dosing:
herpesSimplexInitial:
200 mg orally 5 times a day for 10 days
herpesSimplexRecurrent:
200 mg orally 5 times a day for 5 days OR 400 mg orally 3 times a day for 5 days
herpesSimplexSuppression:
400 mg orally twice daily (or 200 mg 3-5 times daily) for up to 12 months
herpesZosterShingles:
800 mg orally 5 times a day for 7 to 10 days
varicellaChickenpox:
800 mg orally 5 times a day for 5 days
Pediatric Dosing
Neonatal:
Not established for oral capsules; IV dosing used for severe infections.
Infant:
Not established for oral capsules; IV dosing used for severe infections.
Child:
Varicella (2 years and older): 20 mg/kg orally 4 times a day for 5 days (max 800 mg/dose).
Adolescent:
Dosing generally follows adult recommendations for specific indications (e.g., genital herpes, zoster) if weight-based dosing is not specified.
Dose Adjustments
Renal Impairment:
Mild:
CrCl 25-50 mL/min: Adjust dose frequency (e.g., for 200 mg 5x/day, give 200 mg 3x/day).
Moderate:
CrCl 10-25 mL/min: Adjust dose frequency (e.g., for 200 mg 5x/day, give 200 mg 2x/day).
Severe:
CrCl <10 mL/min: Adjust dose frequency (e.g., for 200 mg 5x/day, give 200 mg once daily).
Dialysis:
Hemodialysis: Administer dose after dialysis. Peritoneal dialysis: No supplemental dose needed.
Hepatic Impairment:
Mild:
No adjustment
Moderate:
No adjustment
Severe:
No adjustment
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 selectively phosphorylated to the active triphosphate form by viral thymidine kinase. Acyclovir triphosphate then inhibits viral DNA polymerase, competitively with deoxyguanosine triphosphate, and is incorporated into viral DNA, resulting in chain termination.
Pharmacokinetics
Absorption:
Bioavailability:
15-30% (dose-dependent, 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
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 clearance (glomerular filtration and tubular secretion).
ExcretionRoute:
Renal
Unchanged:
62-91%
Pharmacodynamics
OnsetOfAction:
Not directly applicable for antiviral effect; clinical improvement seen within days of therapy initiation.
PeakEffect:
Peak plasma concentrations reached in 1.5-2.5 hours.
DurationOfAction:
Related to half-life and intracellular phosphorylation; requires frequent dosing due to short plasma 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 sensations, such as burning, numbness, or tingling
Changes in speech
Kidney Problems
Severe and potentially life-threatening kidney problems have been reported with this medication. Contact your doctor right away if you experience:
Inability to pass urine
Blood in the urine
Changes in the amount of urine passed
Unexpected weight gain
Blood Problems
Rare but serious blood problems, including thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS), have been reported with this medication. Seek medical attention immediately if you experience:
Feeling very 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 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. Contact your doctor or seek medical attention if you experience:
Upset stomach or vomiting
Feeling tired or weak
Reporting 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 sensations, such as burning, numbness, or tingling
Changes in speech
Kidney Problems
Severe and potentially life-threatening kidney problems have been reported with this medication. Contact your doctor right away if you experience:
Inability to pass urine
Blood in the urine
Changes in the amount of urine passed
Unexpected weight gain
Blood Problems
Rare but serious blood problems, including thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS), have been reported with this medication. Seek medical attention immediately if you experience:
Feeling very 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 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. Contact your doctor or seek medical attention if you experience:
Upset stomach or vomiting
Feeling tired or weak
Reporting 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., little or no urination, painful urination, swelling in your feet or ankles, feeling tired or short of breath)
- Signs of nervous system problems (e.g., confusion, agitation, hallucinations, unusual thoughts or behavior, tremors, 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 safely with all your other medications and health conditions. Never start, stop, or adjust the dosage 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 safely with all your other medications and health conditions. Never start, stop, or adjust the dosage of any medication without first consulting your doctor.
Precautions & Cautions
Important Warnings and Cautions
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, exercise caution when using this medication, 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 does not cure herpes infections. Consult your doctor to understand the treatment goals and expectations.
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 other symptoms of genital herpes. Additionally, genital herpes can still be transmitted even when you do not have visible symptoms. To reduce 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 liquids every day, unless your doctor advises you to limit your fluid intake.
If you are 65 years or older, exercise caution when using this medication, 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 does not cure herpes infections. Consult your doctor to understand the treatment goals and expectations.
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 other symptoms of genital herpes. Additionally, genital herpes can still be transmitted even when you do not have visible symptoms. To reduce the risk of transmission, use a latex or polyurethane condom during sexual activity and consult your doctor for further guidance.
Overdose Information
Overdose Symptoms:
- Nausea
- Vomiting
- Diarrhea
- Headache
- Confusion
- Hallucinations
- Seizures
- Kidney failure (elevated serum creatinine, renal pain)
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 impairment)
- Mycophenolate mofetil (increased concentrations of mycophenolic acid)
Moderate Interactions
- Probenecid (increases acyclovir AUC and decreases renal clearance)
- Cimetidine (increases acyclovir AUC and decreases renal clearance)
- Nephrotoxic agents (e.g., aminoglycosides, NSAIDs, cyclosporine, tacrolimus - increased risk of renal dysfunction)
Monitoring
Baseline Monitoring
Renal function (serum creatinine, BUN)
Rationale: Acyclovir is primarily renally eliminated; dose adjustment is necessary in renal impairment.
Timing: Prior to initiation of therapy, especially in elderly or patients with pre-existing renal conditions.
Hydration status
Rationale: Adequate hydration is important to prevent renal tubular crystallization.
Timing: Prior to and during therapy, especially with IV acyclovir or high oral doses.
Routine Monitoring
Renal function (serum creatinine, BUN)
Frequency: Periodically, especially in patients with renal impairment, elderly, or those receiving concomitant nephrotoxic drugs.
Target: Within patient's baseline or normal limits.
Action Threshold: Significant increase above baseline or normal range; consider dose adjustment or discontinuation.
Signs/symptoms of CNS adverse effects (e.g., lethargy, confusion, tremors, seizures)
Frequency: Daily, especially in patients with renal impairment or high doses.
Target: Absence of new or worsening neurological symptoms.
Action Threshold: Development of new or worsening CNS symptoms; consider dose reduction or discontinuation.
Symptom Monitoring
- Nausea
- Vomiting
- Diarrhea
- Headache
- Dizziness
- Fatigue
- Rash
- Confusion
- Hallucinations
- Seizures
- Renal pain (flank pain)
- Decreased urine output
Special Patient Groups
Pregnancy
Acyclovir is Pregnancy Category B. Extensive post-marketing experience and data from the Acyclovir Pregnancy Registry (closed in 1999) have not shown an increased risk of birth defects or other adverse outcomes. Use during pregnancy should be considered when the benefits outweigh the potential risks.
Trimester-Specific Risks:
First Trimester:
No increased risk of birth defects observed in human studies.
Second Trimester:
Generally considered safe; no specific risks identified.
Third Trimester:
Generally considered safe; no specific risks identified.
Lactation
Acyclovir is excreted into breast milk. The amount ingested by a breastfed infant is generally low and below therapeutic doses for infants. The American Academy of Pediatrics considers acyclovir compatible with breastfeeding. Monitor infant for diarrhea or rash.
Infant Risk:
Low risk (L2)
Pediatric Use
Dosing is weight-based for some indications (e.g., varicella). Neonates and infants with severe infections typically receive IV acyclovir. Close monitoring for adverse effects, especially CNS effects, is important.
Geriatric Use
Elderly patients are more likely to have decreased renal function, which requires dose adjustment. They are also at increased risk for CNS adverse effects (e.g., confusion, lethargy, hallucinations). Monitor renal function and hydration status closely.
Clinical Information
Clinical Pearls
- Acyclovir is most effective when initiated at the earliest sign or symptom of a herpes infection.
- Adequate hydration is crucial, especially with higher doses or in patients with impaired renal function, to prevent renal tubular crystallization.
- Oral acyclovir has low and variable bioavailability, which is why higher doses are often required compared to IV formulations.
- For chronic suppressive therapy of genital herpes, adherence is key to reducing the frequency of outbreaks.
- Acyclovir does not eradicate the latent virus and is not a cure for herpes infections.
Alternative Therapies
- Valacyclovir (prodrug of acyclovir with better bioavailability, allowing less frequent dosing)
- Famciclovir (prodrug of penciclovir, another antiviral with similar spectrum)
Cost & Coverage
Average Cost:
Varies widely, typically $10-$50 per 30 capsules (200mg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (for 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 this 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 emergency medical attention. When seeking help, be prepared to provide details about the overdose, including the medication taken, the amount, and the time it occurred.