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Sitavig Side Effects

Generic Name: acyclovir

Note: This page contains side effects data for the generic drug acyclovir. It is possible that some of the dosage forms included below may not apply to the brand name Sitavig.

For the Consumer

Applies to acyclovir: buccal mucosa tablet

As well as its needed effects, acyclovir (the active ingredient contained in Sitavig) may cause unwanted side effects that require medical attention.

Severity: Major

If any of the following side effects occur while taking acyclovir, check with your doctor immediately:

Less common:
  • Canker sores
  • pain in the gums
  • sores, ulcers, or white spots on the tongue or inside the mouth

Severity: Minor

Some acyclovir side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

Less common:
  • Flushing or redness of the skin
  • rash
  • unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness
  • unusually warm skin

For Healthcare Professionals

Applies to acyclovir: buccal tablet, compounding powder, intravenous powder for injection, intravenous solution, oral capsule, oral suspension, oral tablet


Gastrointestinal side effects have been the most frequently reported side effects, and include nausea, vomiting, abdominal pain, and diarrhea.

Nausea and vomiting have been reported with oral and intravenous administration, and have preceded neurotoxicity and nephrotoxicity. Gagging and anorexia have also been reported.[Ref]


Renal side effects have included renal failure, renal pain (may be associated with renal failure), elevated blood urea nitrogen, elevated serum creatinine, and hematuria. Renal effects generally are transient and resolve over several days following discontinuation of therapy; however fatal renal failure has occurred. Renal damage is most commonly due to crystallization of the drug in the renal tubules. Acute tubular necrosis and interstitial nephritis have also been reported.[Ref]

Transient renal dysfunction has been reported with both oral and intravenous acyclovir therapy. Crystallization of the drug in renal tubules is thought to be the mechanism for the development of renal dysfunction, based on findings of crystalluria in several case reports and at least one prospective study.

Elderly or renally impaired patients are at greater risk for developing neurotoxicity and further deterioration in renal function.[Ref]

Nervous system

Nervous system side effects have included aggressive behavior, agitation, ataxia, coma, confusion, decreased consciousness, delirium, delusions, disorientation, dizziness, EEG changes, abnormal cerebrospinal fluid findings, encephalopathy, focal neurological signs, hallucinations, headache, insomnia, irritability, lightheadedness, major depression, mania, myoclonus, obtundation, paresthesia, psychosis, seizure, somnolence, tremors, and Cotard's syndrome. Neurotoxicity generally develops early in acyclovir (the active ingredient contained in Sitavig) treatment and has most commonly been reported in patients with renal failure, the elderly, and in patients following bone marrow transplant. It is thought to be associated with high serum concentrations of acyclovir. Guillain Barre syndrome has been reported in at least one patient receiving acyclovir prophylaxis following allogeneic marrow transplantation.[Ref]

Acyclovir neurotoxicity is almost exclusively seen in patients with renal failure. These patients may have longstanding chronic renal failure or acute failure associated with acyclovir. Although more commonly seen with intravenous administration of larger doses, neurotoxicity has also been reported in patients receiving oral doses of acyclovir. Following discontinuation of acyclovir, mental status recovers within about a week. Several patients with chronic renal failure exhibiting neurotoxicity improved dramatically following hemodialysis. In one study of renal transplant patients receiving oral acyclovir therapy, one patient developed neurotoxicity, manifested as disorientation, confusion and myoclonus. The symptoms responded to a decrease in dosage. Three other case reports have also described neurologic symptoms, including visual hallucinations, delusions, mania, tremors, myoclonus and EEG changes, which improved following discontinuation of intravenous acyclovir. Rechallenge in one case using a lower dosage resulted in no sequelae.[Ref]


Local adverse effects associated with intravenous administration of acyclovir (the active ingredient contained in Sitavig) have included inflammation or phlebitis at the injection site. Phlebitis is more common when concentrated solutions (greater than 7 mg/mL) are administered. Skin eruptions have been reported at venipuncture sites and tissue necrosis has occurred after infiltration into extravascular tissues.[Ref]


Cardiovascular side effects have included hypotension.[Ref]


Dermatologic side effects have included alopecia, erythema multiforme, hives, photosensitive rash, pruritus, rash, Stevens-Johnson syndrome, toxic epidermal necrolysis, and urticaria.[Ref]


Hematologic and lymphatic side effects have included anemia, disseminated intravascular coagulation, hemolysis, leukocytoclastic vasculitis, leukocytosis, leukopenia, lymphadenopathy, neutropenia, neutrophilia, thrombocytosis, thrombocytopenia, and pancytopenia.[Ref]


Hepatic side effects have included elevated liver function tests, hepatitis, hyperbilirubinemia, and jaundice.[Ref]


Hypersensitivity reactions have included anaphylaxis.[Ref]


Ocular side effects have included visual abnormalities.[Ref]


Musculoskeletal side effects reported have included myalgia and dysarthria.[Ref]


Other side effects have included angioedema, fever, malaise, pain, fatigue, peripheral edema, and increased lactate dehydrogenase.[Ref]


Genitourinary side effects have included crystalluria.[Ref]


1. Yang HH, Hsiao YP, Shih HC, Yang JH "Acyclovir-induced neuropsychosis successfully recovered after immediate hemodialysis in an end-stage renal disease patient." Int J Dermatol 46 (2007): 883-4

2. Goldberg LH, Kaufman R, Conant MA, et al "Oral acyclovir for episodic treatment of recurrent genital herpes." J Am Acad Dermatol 15 (1986): 256-64

3. Jen SP, Sharma R, Kochar S "Probable acyclovir-induced angioedema in a patient with HIV infection and suspected varicella-zoster virus encephalitis." Am J Health Syst Pharm 68 (2011): 2257-60

4. Boeckh M, Kim HW, Flowers ME, Meyers JD, Bowden RA "Long-term acyclovir for prevention of varicella zoster virus disease after allogeneic hematopoietic cell transplantation - a randomized double-blind placebo controlled study." Blood 107 (2005): 1800-5

5. Bean B, Aeppli D "Adverse effects of high-dose intravenous acyclovir in ambulatory patients with acute herpes zoster." J Infect Dis 151 (1985): 362-5

6. Tyring S, Belanger R, Bezwoda W, Ljungman P, Boon R, Saltzman RL "A randomized, double-blind trial of famciclovir versus acyclovir for the treatment of localized dermatomal herpes zoster in immunocompromised patients." Cancer Invest 19 (2001): 13-22

7. "Product Information. Zovirax (acyclovir)." Glaxo Wellcome, Research Triangle Park, NC.

8. Cohen SM, Minkove JA, Zebley JW, Mulholland JH "Severe but reversible neurotoxicity from acyclovir." Ann Intern Med 100 (1984): 920

9. Krieble BF, Rudy DW, Glick MR, Clayman MD "Case report: acyclovir neurotoxicity and nephrotoxicity--the role for hemodialysis." Am J Med Sci 305 (1993): 36-9

10. Dworkin RH, Johnson RW, Breuer J, et al. "Recommendations for the management of herpes zoster." Clin Infect Dis 44 Suppl 1 (2007): S1-S26

11. Kimberlin DF, Weller S, Whitley R, Andrews WW, Hauth JC, Lakeman F, Miller G "Pharmacokinetics of oral valacyclovir and acyclovir in late pregnancy." Am J Obstet Gynecol 179 (1998): 846-51

12. Johnson GL, Limon L, Trikha G, Wall H "Acute renal failure and neurotoxicity following oral acyclovir." Ann Pharmacother 28 (1994): 460-3

13. Roling J, Schmid H, Fischereder M, Draenert R, Goebel FD "HIV-Associated Renal Diseases and Highly Active Antiretroviral Therapy-Induced Nephropathy." Clin Infect Dis 42 (2006): 1488-95

14. Rashed A, Asadeh B, Romeh SHA "Acyclovir-induced acute tubulo-interstitial nephritis." Nephron 56 (1990): 436-8

15. Lopez PF, Davis JL, Pare R, Kinota S, Lambert HM "Acyclovir induced renal failure in the treatment of presumed viral retinitis." Ann Ophthalmol 27 (1995): 75-84

16. Hernandez JO, Norstrom J, Wysock G "Acyclovir-induced renal failure in an obese patient." Am J Health Syst Pharm 66 (2009): 1288-91

17. Lawson AF, Green PA, Brett AS "Acute renal insufficiency due to oral acyclovir in a man with sickle cell trait." South Med J 92 (1999): 1093-4

18. Straus SE, Dale JK, Tobi M, et al "Acyclovir treatment of the chronic fatigue syndrome: lack of efficacy in a placebo-controlled trial." N Engl J Med 319 (1988): 1692-8

19. Fletcher CV, Chinnock BJ, Chace B, Balfour HH "Pharmacokinetics and safety of high-dose oral acyclovir for suppression of cytomegalovirus disease after renal transplantation." Clin Pharmacol Ther 44 (1988): 158-63

20. Hernandez E, Praga M, Moreno F, Montoyo C "Acute renal failure induced by oral acyclovir." Clin Nephrol 36 (1991): 155-6

21. Bianchetti MG, Roduit C, Oetliker OH "Acyclovir-induced renal failure: course and risk factors." Pediatr Nephrol 5 (1991): 238-9

22. Izzedine H, Launay-Vacher V, Deray G "Antiviral drug-induced nephrotoxicity." Am J Kidney Dis 45 (2005): 804-17

23. Sawyer MH, Webb DE, Balow JE, Straus SE "Acyclovir-induced renal failure." Am J Med 84 (1988): 1067-71

24. Mason WJ, Nickols HH "Images in clinical medicine. Crystalluria from acyclovir use." N Engl J Med 358 (2008): e14

25. Becker BN, Fall P, Hall C, Milam D, Leonard J, Glick A, Schulman G "Rapidly progressive acute renal failure due to acyclovir: case report and review of the literature." Am J Kidney Dis 22 (1993): 611-5

26. Gnann JW, Barton NH, Whitley RJ "Acyclovir: mechanism of action, pharmacokinetics, safety and clinical applications." Pharmacotherapy 3 (1983): 275-83

27. Perazella MA "Drug-induced renal failure: update on new medications and unique mechanisms of nephrotoxicity." Am J Med Sci 325 (2003): 349-62

28. Peterslund NA, Larsen ML, Mygind H "Acyclovir crystalluria." Scand J Infect Dis 20 (1988): 225-8

29. Adair JC, Gold M, Bond RE "Acyclovir neurotoxicity: clinical experience and review of the literature." South Med J 87 (1994): 1227-31

30. Rashiq S, Briewa L, Mooney M, Giancarlo T, Khatib R, Wilson FM "Distinguishing acyclovir neurotoxicity from encephalomyelitis." J Intern Med 234 (1993): 507-11

31. Hellden A, Odar-Cederlof I, Larsson K, Fehrman-Ekholm I, Linden T "Death delusion." BMJ 335 (2007): 1305

32. Ernst ME, Franey RJ "Acyclovir- and ganciclovir-induced neurotoxicity." Ann Pharmacother 32 (1998): 111-3

33. Jones PG, Beier-Hanratty SA "Acyclovir: neurologic and renal toxicity." Ann Intern Med 104 (1986): 892

34. Wade JC, Meyers JD "Neurologic symptoms associated with parenteral acyclovir treatment after marrow transplantation." Ann Intern Med 98 (1983): 921-5

35. MacDiarmaid-Gordon AR, O'Connor M, Beaman M, Ackrill P "Neurotoxicity associated with oral acyclovir in patients undergoing dialysis." Nephron 62 (1992): 280-3

36. Beales P, Almond MK, Kwan JTC "Acyclovir neurotoxicity following oral therapy - prevention and treatment in patients on haemodialysis." Nephron 66 (1994): 362-3

37. Mataix AL, Duarte J, Revuelta K, et al. "Oral acyclovir and neurologic adverse effects in endstage renal disease." Ann Pharmacother 28 (1991): 961-2

38. Papadakis M, Fee P, Wilhelm T, Davenport A, Connolly J "Facial weakness in a haemodialysis patient." Lancet 369 (2007): 714

39. Slifkin M, Doron S, Snydman DR "Viral prophylaxis in organ transplant patients." Drugs 64 (2004): 2763-92

40. Gill MJ, Burgess E "Neurotoxicity of acyclovir in end stage renal disease." J Antimicrob Chemother 25 (1990): 300-1

41. Feldman S, Rodman J, Gregory B "Excessive serum concentrations of acyclovir and neurotoxicity." J Infect Dis 157 (1988): 385-8

42. Fukunishi I, Inada T, Horie Y "Manic symptoms caused by acyclovir in a hemodialysis patient." Nephron 67 (1994): 494

43. Sylvester RK, Ogden WB, Draxler CA, Lewis B "Vesicular eruption: a local complication of concentrated acyclovir infusions." JAMA 255 (1986): 385-6

44. Tomson CR, Goodship TH, Rodger RS "Psychiatric side-effects of acyclovir in patients with chronic renal failure." Lancet 2 (1985): 385-6

45. Mindel A, Carney O. Freris M, Faherty A, Patou G, Williams P "Dosage and safety of long-term suppressive acyclovir therapy for recurrent genital herpes." Lancet Apr (1988): 926-8

46. Fazal BA, Turett GS, Justman JE, Hall G, Telzak EE "Stevens-johnson syndrome induced by treatment with acyclovir." Clin Infect Dis 21 (1995): 1038-9

It is possible that some side effects of Sitavig may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.