Acyclovir is an antiviral medication used to treat infections caused by the herpes family of viruses, such as herpes simplex (cold sores and genital herpes) and varicella-zoster (shingles and chickenpox). It works by interfering with the virus’s ability to replicate, slowing the spread of the infection. Although generally well-tolerated, fatigue or unusual tiredness is a recognized side effect of acyclovir.
Acyclovir and the Experience of Fatigue
Fatigue, defined as a lack of usual energy, is reported as a common side effect of oral acyclovir therapy, affecting up to 10% of users in clinical trials. This tiredness is typically mild to moderate and often lessens as the body adjusts to the medication during the first few days of treatment.
The cause of drowsiness is likely linked to the drug’s effect on the central nervous system (CNS), although the exact mechanism is not fully understood. In rare instances, acyclovir can cross the blood-brain barrier, leading to neurological symptoms like confusion or dizziness, which may cause lethargy.
It is important to note that the underlying viral infection itself, such as a shingles outbreak, often causes profound fatigue. This weakness and lack of energy can be difficult to distinguish from a drug side effect, as the body is fighting the virus.
Other Common Systemic Side Effects
Beyond fatigue, acyclovir can cause other common side effects that affect the body’s systems, especially the gastrointestinal tract. Nausea and vomiting are frequently reported, and some people experience diarrhea or abdominal pain while taking the medication.
These digestive issues are typically mild and temporary, resolving on their own as treatment continues. Other common issues involve the nervous system, such as headaches and dizziness.
Dizziness, in particular, can contribute to a feeling of general malaise or unsteadiness, which might be mistaken for drowsiness. These side effects tend to be most noticeable at the beginning of the treatment course and diminish as the body adjusts to the drug.
Managing Tiredness and When to Seek Medical Advice
For managing mild tiredness or dizziness while taking acyclovir, several practical steps can help improve comfort and safety. Maintaining adequate hydration is important, as dehydration can worsen feelings of fatigue and may also increase the risk of kidney-related side effects.
Avoiding activities that require complete mental alertness, such as operating heavy machinery or driving, is advisable until you know how the medication affects you. It is also strongly recommended to avoid alcohol consumption, as it can intensify side effects, including dizziness and drowsiness.
If the tiredness is mild, continuing with the full course of treatment is important, as stopping the medication prematurely can prevent the infection from being fully treated. You should contact a healthcare provider if the fatigue is so severe that it interferes with daily activities or if it is accompanied by other worrying symptoms.
Signs Requiring Immediate Medical Attention
Immediate medical attention is necessary if you experience signs of a severe reaction or serious adverse effects. These include:
- Difficulty breathing, swelling of the face or throat, or hives.
- Severe neurological symptoms, including confusion, hallucinations, unsteadiness, or seizures.
- Signs of kidney issues, such as a significant decrease in urination or pain in the lower back or side.
Never discontinue the prescribed medication without first speaking to your doctor.