Acyclovir Side Effects

Acyclovir Side Effects

Acyclovir  (or Aciclovir) is an antiviral drug. Acyclovir  is primarily used for the treatment of herpes simplex virus infections (herpes simplex virus 1 and 2), as well as in the treatment of varicella zoster virus, Epstein-Barr virus and cytomegalovirus.

Viruses are intracellular microorganisms, which have their own DNA, and reproduce by repeatedly copying their DNA and replicating all other structures of the virus. Acyclovir  is embedded in the DNA of the virus and prevents further formation of the virus without damaging the human cells.


Indications for systemic therapy: primary and recurrent infections of the skin and mucous membranes caused by the herpes simplex virus (type 1 and 2), which include genital herpes, herpes zoster, and chickenpox. Acyclovir  is used in a combination therapy in patients with severe immunosuppression (such as patients with HIV infection) and in patients that underwent bone marrow transplantation, as well as for prevention of cytomegalovirus infection after bone marrow transplantation.

Indications for external therapy: herpes simplex of the skin and mucous membranes, genital herpes (primary and recurrent); localized herpes zoster (support therapy).

Indications for topical therapy in ophthalmology: herpetic keratitis.

Side effects

Systemic therapy:

Digestive system disorders: nausea, vomiting, diarrhea, abdominal pain, anorexia (abnormal loss of appetite for food, especially as a result of disease).

Nervous system disorders: dizziness, headache, nausea, drowsiness, confusion, hallucinations, seizures, tremors (shaking), depression or psychosis (neurological disorders usually seen in patients with underlying mental states).

Blood system disorders (observed when the drug is injected intravenously): anemia (a deficiency of red blood cells or of hemoglobin in the blood), neutropenia (presence of abnormally few neutrophils in the blood) or neutrophilia (presence of abnormally high neutrophils in the blood), thrombocytopenia (abnormally low number of platelets in the blood) or thrombocytosis (abnormally high number of platelets in the blood) or leukocytosis (abnormally high white blood cell count), DIC (disseminated intravascular coagulation), hemolysis (destruction of red blood cells).

Cardiovascular system disorders: lower blood pressure.

Genitourinary system disorders: transient (temporary) increase in blood urea nitrogen and serum creatinine levels, acute renal failure (often occurs under fast intravenous injection), hematuria (presence of blood in urine).

Other reactions: myalgia (pain in a muscle or group of muscles), paresthesia (abnormal sensations, such as burning, tingling, or a “pins-and-needles” feeling at various sites), alopecia, skin allergic reactions (pruritus, rash, urticaria), impaired vision, fever, lymphadenopathy (swollen lymph nodes), peripheral edema, reactions at the intravenous injection site: phlebitis or local inflammation (pain, swelling or redness), necrosis (when the drug enters under the skin).

Severe allergic reactions: anaphylaxis, Lyell’s syndrome.

External therapy:

Skin and mucous membranes: pain, burning, itching, rash, vulvitis (inflammation of the vulva).

When applied as an eye ointment: burning at the site of application, conjunctivitis, superficial punctate keratopathy.

Laboratory abnormalities:

  • Elevated ALT
  • Elevated AST
  • Elevated bilirubin
  • Anemia
  • Neutropenia or neutrophilia
  • Thrombocytopenia  or thrombocytosis
  • Leukocytosis
  • Increase in blood urea nitrogen and serum creatinine levels
  • Hematuria

Side effects during pregnancy and breast-feeding

Acyclovir  can be taken during pregnancy if the expected effect of therapy outweighs the potential risk to the fetus (no adequate and strictly controlled studies on the safety of the drug in pregnant women have been conducted). Acyclovir  passes through the placenta. Data on the outcome of pregnancy in women taking systemic Acyclovir  in the first trimester of pregnancy showed no increase in birth defects in children compared with the general population. Since the observation included a small number of women, conclusions that Acyclovir  is safe for pregnant women cannot be regarded as reliable and definitive.

Acyclovir  passes into breast milk and its content in the milk is close to its concentration in the blood. Children who are breastfed can receive Acyclovir  at full doses. Given this, Acyclovir  is used in nursing women only when necessary.

Side effects in the elderly

Nervous system disorders are the common side effects in the elderly.


Symptoms: headache, neurological disorders, shortness of breath, nausea, vomiting, diarrhea, kidney failure, seizures, coma.

Warnings and recommendations

During Acyclovir  therapy, it is recommended to take plenty of fluids (in order to prevent sedimentation of Acyclovir  in the renal tubules).

Acyclovir  is not recommended for use in the treatment of children with chicken pox if the disease is mild.

During treatment of genital herpes, you should avoid sex or use condoms, because Acyclovir  does not prevent transmission of the virus to the partner.

When taking Acyclovir, you should monitor the renal function (checking the level of blood urea nitrogen and serum in the blood plasma).

Acyclovir  and alcohol

Acyclovir is metabolized in the liver by the enzyme alcohol dehydrogenase, which, as its name suggests, plays a role in the splitting of alcohol. In patients with chronic alcoholism, splitting of Acyclovir  will be complicated, and the likelihood of side effects occurring will be higher.