|Systematic (IUPAC) name|
|Licence data||US FDA:|
|Pregnancy cat.||B3 (AU) B (US)|
|Legal status||unscheduled (CREAM FORM under 10g ) (AU) ℞-only (CA) GSL (CREAM FORM under 2g ) (UK) ℞-only (US)|
|Routes||Intravenous, oral, topical (including eye ointment)|
|Excretion||Renal (62-90% as unchanged drug)|
|ATC code||J05 D06 S01|
|PDB ligand ID||AC2 (, )|
|Mol. mass||225.21 g/mol|
|Melt. point||256.5 °C (494 °F)|
|(what is this?)|
Aciclovir (INN, BAN. Brand names: Cyclovir, Herpex, Acivir, Acivirax, Zovirax, Zoral, Xovir and Imavir) // or acyclovir (USAN, former BAN), chemical name acycloguanosine, abbreviated as ACV, is a guanosine analogue antiviral drug. It is one of the most commonly used antiviral drugs, that is primarily used for the treatment of herpes simplex virus infections, as well as in the treatment of varicella zoster (chickenpox) and herpes zoster (shingles).
- Genital herpes simplex (treatment and prevention)
- Herpes simplex labialis (cold sores)
- Acute chickenpox in immunocompromised patients
- Herpes simplex encephalitis
- Acute mucocutaneous HSV infections in immunocompromised patients
- Herpes of the eye
- Herpes simplex blepharitis (a chronic (long-term) form of herpes eye infection)
- Prophylaxis against herpesviruses in immunocompromised patients (such as patients undergoing cancer chemotherapy)
It has been claimed that the evidence for the effectiveness of topically applied cream for recurrent labial outbreaks is weak. An earlier review of scientific literature showed there is some effect in reducing the number and duration of lesions if aciclovir is applied at an early stage of an outbreak. Aciclovir trials show that this agent has no role in preventing HIV transmission, but it can help slow HIV disease progression in people not taking anti-retroviral therapy (ART). This finding emphasizes the importance of testing simple, inexpensive non-ART strategies, such as aciclovir and cotrimoxazole, in people with HIV.
Its use in pregnancy is advised against unless the benefits to the mother outweigh the danger to the fetus. Studies in mice, rabbits and rats (with doses more than 10 times the equivalent of that used in humans) given during organogenesis have failed to demonstrate birth defects. Studies in rats in which they were given the equivalent to 63 times the standard steady-state humans concentrations of the drug[Note 1] on day 10 of gestation showed head and tail anomalies.
Common adverse drug reactions (≥1% of patients) associated with systemic aciclovir therapy (oral or IV) include: nausea, vomiting, diarrhoea, encephalopathy (with IV use only), injection site reactions (with IV use only) and headache. In high doses, hallucinations have been reported. Infrequent adverse effects (0.1–1% of patients) include: agitation, vertigo, confusion, dizziness, oedema, arthralgia, sore throat, constipation, abdominal pain, hair loss, rash and weakness. Rare adverse effects (<0.1% of patients) include: coma, seizures, neutropenia, leukopenia, crystalluria, anorexia, fatigue, hepatitis, Stevens–Johnson syndrome, toxic epidermal necrolysis, thrombotic thrombocytopenic purpura and anaphylaxis.
Intravenous aciclovir may cause reversible nephrotoxicity in up to 5% to 10% of patients because of precipitation of aciclovir crystals in kidney. Aciclovir crystalline nephropathy is more common when aciclovir is given as a rapid infusion and in patients with dehydration and preexisting renal impairment. Adequate hydration, a slower rate of infusion, and dosing based on renal function may reduce this risk.
Aciclovir topical cream is commonly associated (≥1% of patients) with: dry or flaking skin or transient stinging/burning sensations. Infrequent adverse effects include erythema or itch. When applied to the eye, aciclovir is commonly associated (≥1% of patients) with transient mild stinging. Infrequently (0.1–1% of patients), ophthalmic aciclovir is associated with superficial punctate keratitis or allergic reactions.
Detection in biological fluids
Aciclovir may be quantitated in plasma or serum to monitor for drug accumulation in patients with renal dysfunction or to confirm a diagnosis of poisoning in acute overdose victims.
Mechanism of action
Aciclovir is converted by viral thymidine kinase to aciclovir monophosphate, which is then converted by host cell kinases to aciclovir triphosphate (ACV-TP). ACV-TP, in turn, competitively inhibits and inactivates DNA polymerases and incorporates itself into viral DNA chain.
- Herpes simplex virus type I (HSV-1)
- Herpes simplex virus type II (HSV-2)
- Varicella zoster virus (VZV)
- Epstein-Barr virus (EBV)
- Cytomegalovirus (CMV) – least activity
Resistance to aciclovir is rare, but is more common in patients on chronic antiviral prophylaxis (transplant recipients, people with acquired immunodeficiency syndrome due to HIV infection). Mechanisms of resistance in HSV include deficient viral thymidine kinase; and mutations to viral thymidine kinase or DNA polymerase, altering substrate sensitivity.
Aciclovir is poorly water soluble and has poor oral bioavailability (15–30%), hence intravenous administration is necessary if high concentrations are required. When orally administered, peak plasma concentration occurs after 1–2 hours. Aciclovir has a high distribution rate; protein binding is reported to range from 9 to 33%. The elimination half-life (t1/2) of aciclovir depends according to age group; neonates have a t1/2 of 4 hours, children 1-12 years have a t1/2 of 2-3 hours whereas adults have a t1/2 of 3 hours.
Aciclovir was seen as the start of a new era in antiviral therapy, as it is extremely selective and low in cytotoxicity. Nucleosides isolated from a Caribbean sponge, Cryptotethya crypta, were the basis for the synthesis of aciclovir. It was codiscovered by Howard Schaffer following his work with Robert Vince, S. Bittner and S. Gurwara on the adenosine analog acycloadenosine which showed promising antiviral activity. Later, Schaffer joined Burroughs Wellcome and continued the development of aciclovir with pharmacologist Gertrude B. Elion. A U.S. patent on aciclovir listing Schaffer as inventor was issued in 1979.
Vince later went on to invent abacavir, an nRTI drug for HIV patients. Elion was awarded the 1988 Nobel Prize in Medicine, partly for the development of aciclovir. Richard Whitley, a University of Alabama at Birmingham researcher and pioneer in antiviral therapy, was the first to successfully use the drug in humans.
- Subject to the same conditions as before
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