Aciclovir chemical structure
Find information on thousands of medical conditions and prescription drugs.

Aciclovir

Aciclovir (INN) or acyclovir (USAN), marketed as Zovirax®, is one of the main antiviral drugs. Its discovery has been seen as the start of a new era in antiviral therapy, as it is extremely selective and low in cytotoxicity. However, it has a very narrow spectrum, only effective against certain viruses such as HSV-1, HSV-2, and VZV, with limited effectiveness against active EBV, and has hardly any effect against human cytomegalovirus (CMV). It is about 10 times more potent against HSV than VZV. more...

Home
Diseases
Medicines
A
8-Hour Bayer
Abacavir
Abamectin
Abarelix
Abciximab
Abelcet
Abilify
Abreva
Acamprosate
Acarbose
Accolate
Accoleit
Accupril
Accurbron
Accure
Accuretic
Accutane
Acebutolol
Aceclidine
Acepromazine
Acesulfame
Acetaminophen
Acetazolamide
Acetohexamide
Acetohexamide
Acetylcholine chloride
Acetylcysteine
Acetyldigitoxin
Aciclovir
Acihexal
Acilac
Aciphex
Acitretin
Actifed
Actigall
Actiq
Actisite
Actonel
Actos
Acular
Acyclovir
Adalat
Adapalene
Adderall
Adefovir
Adrafinil
Adriamycin
Adriamycin
Advicor
Advil
Aerobid
Aerolate
Afrinol
Aggrenox
Agomelatine
Agrylin
Airomir
Alanine
Alavert
Albendazole
Alcaine
Alclometasone
Aldomet
Aldosterone
Alesse
Aleve
Alfenta
Alfentanil
Alfuzosin
Alimta
Alkeran
Alkeran
Allegra
Allopurinol
Alora
Alosetron
Alpidem
Alprazolam
Altace
Alteplase
Alvircept sudotox
Amantadine
Amaryl
Ambien
Ambisome
Amfetamine
Amicar
Amifostine
Amikacin
Amiloride
Amineptine
Aminocaproic acid
Aminoglutethimide
Aminophenazone
Aminophylline
Amiodarone
Amisulpride
Amitraz
Amitriptyline
Amlodipine
Amobarbital
Amohexal
Amoxapine
Amoxicillin
Amoxil
Amphetamine
Amphotec
Amphotericin B
Ampicillin
Anafranil
Anagrelide
Anakinra
Anaprox
Anastrozole
Ancef
Android
Anexsia
Aniracetam
Antabuse
Antitussive
Antivert
Apidra
Apresoline
Aquaphyllin
Aquaphyllin
Aranesp
Aranesp
Arava
Arestin
Arestin
Argatroban
Argatroban
Argatroban
Argatroban
Arginine
Arginine
Aricept
Aricept
Arimidex
Arimidex
Aripiprazole
Aripiprazole
Arixtra
Arixtra
Artane
Artane
Artemether
Artemether
Artemisinin
Artemisinin
Artesunate
Artesunate
Arthrotec
Arthrotec
Asacol
Ascorbic acid
Asmalix
Aspartame
Aspartic acid
Aspirin
Astemizole
Atacand
Atarax
Atehexal
Atenolol
Ativan
Atorvastatin
Atosiban
Atovaquone
Atridox
Atropine
Atrovent
Augmentin
Aureomycin
Avandia
Avapro
Avinza
Avizafone
Avobenzone
Avodart
Axid
Axotal
Azacitidine
Azahexal
Azathioprine
Azelaic acid
Azimilide
Azithromycin
Azlocillin
Azmacort
Aztreonam
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z

It does not eradicate latent herpes, and does not work very well against genital herpes in women. Aciclovir is rather different from other nucleoside analogues, for it contains only a partial nucleoside structure as the sugar ring is replaced by an open-chain structure.

Mode of action

Aciclovir is converted into monophosphate form only by viral thymidine kinase, which is far more effective (3000 times) in phosphorylation than cellular thymidine kinase. Subsequently, the monophosphate form is further phosphorylated into the active triphosphate form, aciclo-GTP, by cellular kinases. Aciclo-GTP is a very potent inhibitor of viral DNA polymerase; it has approximately 100 times higher affinity to viral than cellular polymerase. Its monophosphate form also incorporates into the viral DNA, resulting in chain termination. It has also been shown that the viral enzymes cannot remove acyclo-GMP from the chain, which results in inhibition of further activity of DNA polymerase. Acyclo-GTP is fairly rapidly metabolised within the cell, possibly by cellular phosphatases.

Pharmacokinetics

Aciclovir suffers from low water solubility, and also from poor oral absorption, which is only 20%. Orally administered the peak plasma concentration will be reached in 1-2 hours. If large doses are required, aciclovir must be administered intravenously. Aciclovir has a high distribution rate, only 30 % is protein-bound in plasma. The half-life of aciclovir is approximately 3 hours. Aciclovir can also be given topically for treatment of herpes infections of mucous membrane and skin, such as genital herpes or recurrent herpes labialis (cold sore). Prophylactic administration is possible, and is often used for patients who are under immunosuppressant drugs or radiotherapy or for those who are suffering from recurrent genital infection herpes simplex.

Metabolism

The excretion of aciclovir takes place via the renal system, partly by glomerular filtration and partly by tubular secretion. Renal problems have been reported when given in large, fast doses intravenously, due to the crystallisation of aciclovir in the kidneys.

Side effects

Since aciclovir can be incorporated also into the cellular DNA, it is a chromosome mutagen, therefore, its use should be avoided during pregnancy. However it has not been shown to cause any teratogenic nor carcinogenic effects. The acute toxicity (LD50) of aciclovir when given orally is greater than 1mg/kg, due to the low absorption rate from the gastrointestinal tract. Single cases have been reported, where extremely high (up to 80mg/kg) doses have been accidentally given intravenously without causing any side effects. The most common adverse effects are local irritation at the site of injection, headache when given orally, and a stinging and burning sensation when administered topically. The resistance towards aciclovir evolves rather rapidly, although this has not much hindered its clinical use. Resistant forms are most likely viruses that have a mutation in their thymidine kinase or DNA polymerase.

Read more at Wikipedia.org


[List your site here Free!]


Are drug therapies effective in treating Bell's palsy? - Clinical Inquiries
From Journal of Family Practice, 2/1/03 by Scott Shannon

* Photocopy for your patients "Bell's palsy" on page 160.

* EVIDENCE-BASED ANSWER

Early use of corticosteroid therapy results in less autonomic synkinesis and possibly improved rates of recovery in adults (strength of recommendation: C); there is no proven benefit in children (SOR: B).

Adding acyclovir (Zovirax) to prednisone therapy may improve recovery rates compared with prednisone alone (SOR: C).

The results of 1 nonblinded study indicate that intramuscular methylcobalamin (vitamin [B.sub.12]) used alone or in combination with prednisone may shorten time to recovery (SOR: C).

* EVIDENCE SUMMARY

Bell's palsy is a lower motor neuron disease of the facial nerve characterized by a transient paralysis. Healing is occasionally incomplete, resulting in residual nerve dysfunction, including partial palsy and motor synkinesis (involuntary movement accompanying a voluntary one) and autonomic synkinesis (involuntary lacrimation after a voluntary muscle movement). Bell's palsy is associated with significant edema and ischemia of the facial nerve as it passes through its bony canal.

Herpes simplex reactivation has been shown to be associated with a large proportion of cases.

Corticosteroids are the most studied form of therapy for Bell's palsy (Table). Early work in England culminated in 1971 with a well-performed study demonstrating lower rates of incomplete recovery with prednisolone compared with corticotropkin. (1) A potentially definitive randomized controlled trial in 1970 was stopped prematurely because of investigators' subjective impression that prednisone markedly reduced postauricular pain. (2) Subsequently, the highest-quality study had few patients (n=51) and reported no difference in outcomes between patients receiving 10 days of oral prednisone plus vitamins and those receiving vitamins alone. (3)

One open randomized controlled trial demonstrated shorter mean recovery times with intramuscular methylcobalamin (1.95 weeks) and methylcobalamin plus prednisone (2.0 weeks) compared with prednisone alone (9.6 weeks). (4) Another trial of 239 patients showed improved rates of autonomic synkinesis after treatment with 16 days of prednisone compared with placebo. (5)

A randomized, controlled trial of children 2 to 6 years of age found no significant differences in short-term recovery after treatment with methylprednisolone compared with untreated controls. (6) Eventually, all these children recovered normal facial nerve function within 12 months.

Two randomized controlled trials have assessed the efficacy of acyclovir for treatment of Bell's palsy. One trial compared prednisone with acyclovir and found patients treated with prednisone had better complete recovery rates, 93.6% versus 77.7% (absolute risk reduction [ARR]=15.9%, 95% confidence interval [CI]=2.8%-29%], number needed to treat [NNT]=7). (7)

Another study demonstrated that the combination of prednisone and acyclovir had greater complete recovery rates compared with prednisone alone (92% vs. 76%, ARR=16%, 95% CI=1.7%-30.3%, NNT=7). (8)

Overall, the data suggest corticosteroid therapy may provide a small clinical benefit in adult patients with Bell's palsy. In many of these studies, patients who had contraindications to steroid therapy (peptic ulcer disease, uncontrolled diabetes, hypertension, or immunosuppression) were excluded.

If no contraindications to steroids exist, it is resonable to initiate treatment with corticosteroids for an adult patient with new-onset Bell's palsy. Most studies have started patients on steroids within 10 days of onset of symptoms.

* RECOMMENDATIONS FROM OTHERS

A practice parameter from the American Academy of Neurology states that steroids are safe and probably effective (SOR: B), whereas acyclovir is safe and possibly effective (SOR: C). (9) Systematic reviews from the Cochrane Database report that available evidence from randomized controlled trials does not show significant benefit from treating Bell's palsy with corticosteroids and that clinical trials on acyclovir are inconclusive and therefore cannot be used to make recommendations regarding its use. (10,11)

* CLINICAL COMMENTARY

My practice of neurology began before the era of corticosteroid treatment for Bell's palsy. Despite the lack of convincing evidenced-based data, it is my clinical impression that there are far fewer patients today with incompletely resolved Bell's palsy than before the widespread use of steroids. Permanent facial deformities seemed more common back then. Therefore, in the absence of harmful effects, I will continue treating with steroids.

Steven H. Horowitz, MD, University of Vermont College of Medicine, Burlington.

REFERENCES

(1.) Taverner D, Cohen SB, Hutchinson BC. Comparison of corticotrophin and prednisolone in treatment of idiopathic facial paralysis (Bell's palsy). Br Med J 1971; 4:20-2.

(2.) Adour KK, Wingerd J, Bell DN, Manning JJ, Hurley JP. Prednisone treatment for idiopathic facial paralysis (Bell's palsy). N Engl J Med 1972; 287:1268-72.

(3.) May M, Wette R, Hardin WB, Jr., Sullivan J. The use of steroids in Bell's palsy: a prospective controlled study. Laryngoscope 1976; 86:1111-22.

(4.) Jalaludin MA. Methylcobalamin treatment of Bell's palsy. Methods Find Exp Clin Pharmacol 1995; 17:539-44.

(5.) Wolf SM, Wagner JH, Davidson S, Forsythe A. Treatment of Bell palsy with prednisone: a prospective, randomized study. Neurology 1978; 28:158-61.

(6.) Unuvar E, Oguz F, Sidal M, Kilic A. Corticosteroid treatment of childhood Bell's palsy. Pediatr Neurol 1999; 21:814-6.

(7.) De Diego JI, Prim MP, De Sarria MJ, Madero R, Gavilan J. Idiopathic facial paralysis: a randomized, prospective, and controlled study using single-dose prednisone versus acyclovir three times daily. Laryngoscope 1998; 108:573-5.

(8.) Adour KK, Rubayaines JM; Von Doersten PG, Byl FM, Trent CS, Quesenberry CP Jr. et al. Bell's palsy treatment with acyclovir and prednisone compared with prednisone alone: a double-blind, randomized, controlled trial. Ann Otol Rhinol Laryngol 1996; 105:371-8.

(9.) Grogan PM. Gronseth GS. Practice parameter: Steroids, acyclovir, and surgery for Bell's palsy (an evidence-based review). Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology 2001; 56:830 6.

(10.) Salinas RA, Alvarez G, Alvarez MI, Ferreira J. Corticosteroids for Bell's palsy (idiopathic facial paralysis) (Cochrane Review). In: The Cochrane Library, Issue 2, 2002. Oxford: Update Software. Updated quarterly.

(11.) Sipe J, Dunn L. Aciclovir for Bell's palsy (idiopathic facial paralysis) (Cochrane Review). In: The Cochrane Library, Issue 2, 2002. Oxford: Update Software. Updated quarterly.

Scott Shannon, MD, Dept of Family and Community Medicine University of Missouri, Columbia. E-mail: shannons@health.missouri.edu. Susan Meadows, MLS, Dept of Family and Community Medicine, University of Missouri, Columbia. E-mail: meadowss@health.missouri.edu.

COPYRIGHT 2003 Dowden Health Media, Inc.
COPYRIGHT 2003 Gale Group

Return to Aciclovir
Home Contact Resources Exchange Links ebay