Inosine pranobex

Inosine pranobex acts as an immunostimulant, an analog of thymus hormones.{{cite web| work = American Cancer Society |title=Inosine Pranobex |url= http://www.cancer.org/treatment/treatmentsandsideeffects/complementaryandalternativemedicine/pharmacologicalandbiologicaltreatment/inosine-pranobex |archive-url=https://web.archive.org/web/20100823035720/http://www.cancer.org/Treatment/TreatmentsandSideEffects/ComplementaryandAlternativeMedicine/PharmacologicalandBiologicalTreatment/inosine-pranobex |archive-date=23 August 2010 |access-date=31 July 2013 }} It is indicated for an entire spectrum of patients with clinical manifestations of immune deficiency. It modulates the immune system by immunostimulation or immunooptimisation of defensive inflammation{{cite book | vauthors = Krejsek J, Andrýs C, Krčmová I | title = Imunologie člověka | trans-title = Human immunology | location = Czechia | publisher = Garamon sro, Hradec Králové | date = 2016 | oclc = 982100822 |language=cs }} at the cellular level, e.g. by interfering with energy metabolism, cell signalling and proliferation.

One of the main immunostimulatory effects of inosine pranobex lies in T-cell modulation.{{cite journal | vauthors = Sliva J, Pantzartzi CN, Votava M | title = Inosine Pranobex: A Key Player in the Game Against a Wide Range of Viral Infections and Non-Infectious Diseases | journal = Advances in Therapy | volume = 36 | issue = 8 | pages = 1878–1905 | date = August 2019 | pmid = 31168764 | pmc = 6822865 | doi = 10.1007/s12325-019-00995-6 }} Its administration has been shown both in vivo and in vitro to induce Th1 cell-type response, as evidenced by the increase in pro-inflammatory cytokines (e.g. IL-2, ILN-γ) in mitogen- or antigen-activated cells.{{cite journal | vauthors = Petrova M, Jelev D, Ivanova A, Krastev Z | title = Isoprinosine affects serum cytokine levels in healthy adults | journal = Journal of Interferon & Cytokine Research | volume = 30 | issue = 4 | pages = 223–228 | date = April 2010 | pmid = 20038210 | doi = 10.1089/jir.2009.0057 }} As such, T-cell maturation and differentiation is further fostered.{{cite journal | vauthors = You Y, Wang L, Li Y, Wang Q, Cao S, Tu Y, Li S, Bai L, Lu J, Wei Z, Chen W, Hao F | title = Multicenter randomized study of inosine pranobex versus acyclovir in the treatment of recurrent herpes labialis and recurrent herpes genitalis in Chinese patients | journal = The Journal of Dermatology | volume = 42 | issue = 6 | pages = 596–601 | date = June 2015 | pmid = 25819042 | doi = 10.1111/1346-8138.12845 }} The increase of ILN-γ in serum is proven to inhibit the production of IL-10,{{cite journal | vauthors = Sabat R, Grütz G, Warszawska K, Kirsch S, Witte E, Wolk K, Geginat J | title = Biology of interleukin-10 | journal = Cytokine & Growth Factor Reviews | volume = 21 | issue = 5 | pages = 331–344 | date = October 2010 | pmid = 21115385 | doi = 10.1016/j.cytogfr.2010.09.002 | url = http://www.hzg.de/imperia/md/content/gkss/zentrale_einrichtungen/bibliothek/journals/2010/Sabat-cytgrowthfactrev.pdf }} which could explain the drug's suppressive effect on anti-inflammatory cytokines.

It also modulates components of innate immunity. In respect to natural killer cells, both population{{cite journal | vauthors = Rumel Ahmed S, Newman AS, O'Daly J, Duffy S, Grafton G, Brady CA, John Curnow S, Barnes NM, Gordon J | title = Inosine Acedoben Dimepranol promotes an early and sustained increase in the natural killer cell component of circulating lymphocytes: A clinical trial supporting anti-viral indications | journal = International Immunopharmacology | volume = 42 | pages = 108–114 | date = January 2017 | pmid = 27912146 | doi = 10.1016/j.intimp.2016.11.023 }} and activity{{cite journal | vauthors = Hersey P, Edwards A | title = Effect of isoprinosine on natural killer cell activity of blood mononuclear cells in vitro and in vivo | journal = International Journal of Immunopharmacology | volume = 6 | issue = 4 | pages = 315–320 | date = January 1984 | pmid = 6207121 | doi = 10.1016/0192-0561(84)90048-1 }} increased as a result of inosine pranobex therapy.{{cite journal | vauthors = Rumel Ahmed S, Newman AS, O'Daly J, Duffy S, Grafton G, Brady CA, John Curnow S, Barnes NM, Gordon J | title = Inosine Acedoben Dimepranol promotes an early and sustained increase in the natural killer cell component of circulating lymphocytes: A clinical trial supporting anti-viral indications | journal = International Immunopharmacology | volume = 42 | pages = 108–114 | date = January 2017 | pmid = 27912146 | doi = 10.1016/j.intimp.2016.11.023 }} It has also been proven that other cells of the innate immunity are affected,{{cite journal | vauthors = Tsang KY, Pan JF, Swanger DL, Fudenberg HH | title = In vitro restoration of immune responses in aging humans by isoprinosine | journal = International Journal of Immunopharmacology | volume = 7 | issue = 2 | pages = 199–206 | date = January 1985 | pmid = 2409037 | doi = 10.1016/0192-0561(85)90027-X }} as neutrophil, monocyte and macrophage chemotaxis and phagocytosis were enhanced in cancer patients.{{cite journal | vauthors = Tsang KY, Fudenberg HH, Pan JF, Gnagy MJ, Bristow CB | title = An in vitro study on the effects of isoprinosine on immune responses in cancer patients | journal = International Journal of Immunopharmacology | volume = 5 | issue = 6 | pages = 481–490 | date = January 1983 | pmid = 6198297 | doi = 10.1016/0192-0561(83)90041-3 }}

Inosine pranobex also has direct antiviral properties. Several hypotheses have been formed over time, but all of them agree that the drug has direct effect on viral RNA synthesis via inhibiting transcription and translation of the genetic code at cellular level.{{cite journal | vauthors = You Y, Wang L, Li Y, Wang Q, Cao S, Tu Y, Li S, Bai L, Lu J, Wei Z, Chen W, Hao F | title = Multicenter randomized study of inosine pranobex versus acyclovir in the treatment of recurrent herpes labialis and recurrent herpes genitalis in Chinese patients | journal = The Journal of Dermatology | volume = 42 | issue = 6 | pages = 596–601 | date = June 2015 | pmid = 25819042 | doi = 10.1111/1346-8138.12845 }}

In fact, cellular RNA and protein synthesis are markedly depressed shortly after viral infection, as the cell is instructed to focus resources on producing viral RNA instead. Inosine pranobex is believed to override this mechanism and incentivize cellular RNA synthesis over viral.{{cite journal | vauthors = Ohnishi H, Kosuzume H, Inaba H, Okura M, Morita Y, Mochizuki H, Suzuki Y | title = Mechanism of host defense suppression induced by viral infection: mode of action of inosiplex as an antiviral agent | journal = Infection and Immunity | volume = 38 | issue = 1 | pages = 243–250 | date = October 1982 | pmid = 6183209 | pmc = 347725 | doi = 10.1128/iai.38.1.243-250.1982 }}{{cite journal | vauthors = Gordon P, Brown ER | title = The antiviral activity of isoprinosine | journal = Canadian Journal of Microbiology | volume = 18 | issue = 9 | pages = 1463–1470 | date = September 1972 | pmid = 4341918 | doi = 10.1139/m72-224 }} It has been suggested that the drug itself, or any one of its components, directly acts on the ribosomes of infected cells providing an advantage to cellular RNA in competition for synthesis. This could also result in errors in the viral RNA transcription, which would hinder viral proliferation as well.{{cite book | vauthors = DeSimone C, Hadden JW | chapter = Prohost Modulation of Immunity by Isoprinosine and NPT 15392 |date=1987 | title = Antibiosis and Host Immunity |pages=279–290 |place=Boston, MA |publisher=Springer US |isbn=978-1-4612-9058-2 |doi=10.1007/978-1-4613-1901-6_32 }}

Another hypothesis suggests that inosine itself has direct antiviral properties, as evidenced by the rather fast metabolism of the compound.It is assumed that the drug breaks down metabolically into its constituents, therefore permitting direct inosine action. Inosine is proven to act on ribosome directly,{{cite journal | vauthors = Licht K, Hartl M, Amman F, Anrather D, Janisiw MP, Jantsch MF | title = Inosine induces context-dependent recoding and translational stalling | journal = Nucleic Acids Research | volume = 47 | issue = 1 | pages = 3–14 | date = January 2019 | pmid = 30462291 | doi = 10.1093/nar/gky1163 }} as such one theory suggests that it inhibits the synthesis of phosphoribosyl pyrophosphate from ribose phosphate, the former being an intermediate in the biosynthesis of purine nucleotides such as adenylate and guanylate. A 2014 study{{cite journal | vauthors = Alseth I, Dalhus B, Bjørås M | title = Inosine in DNA and RNA | journal = Current Opinion in Genetics & Development | volume = 26 | pages = 116–123 | date = June 2014 | pmid = 25173738 | doi = 10.1016/j.gde.2014.07.008 | doi-access = free }} has also shown that inosine affects DNA and RNA directly, as such the wobble mechanism, in which inosine replaces adenine, might result in errors in viral RNA furthermore.

It is apparent that inosine pranobex acts on the viral replication through many mechanisms, and is as such pleiotropic in nature. Most of these mechanisms are not specific to certain viruses and as such the drug is potent in treating a wide spectrum of viral infections, something that is rather uncommon for antivirals, as they tend to be very specific in their target. These mechanisms are also so general that no virus has been ever shown to develop resistance to them.

Macroscopically, antiviral activity has been documented in vivo on several animal models, and experimentally tested on the cytomegalovirus and influenza disease strains. In vitro, there is antiviral activity documented for many RNA and DNA viruses including, but not limited to: herpes simplex virus, cytomegalovirus, adenovirus, poliovirus, and influenza A and B viruses.{{cite journal | vauthors = Muldoon RL, Mezny L, Jackson GG | title = Effect of isoprinosine against influenza and some other viruses causing respiratory diseases | journal = Antimicrobial Agents and Chemotherapy | volume = 2 | issue = 3 | pages = 224–228 | date = September 1972 | pmid = 4790561 | pmc = 444295 | doi = 10.1128/AAC.2.3.224 }}

For patients with sub-optimally functioning immune systems, inosine pranobex can also be helpful in managing and decreasing the incidence{{cite journal | vauthors = Osidak LV, Obraztsova EV | title = Efficacy of the Inosine pranobex molecule in therapeutic and pediatric practice. | journal = Èpidemiologiâ i Infekcionnye Bolezni. Aktual'nye voprosy. | trans-journal = Epidemiology and Infectious Diseases. Current Items |language=ru | date = April 2012 | volume = 15 | issue = 4 | pages = 26-32 https://journals.eco-vector.com/2226-6976/article/view/275885 }} of common viral infections, such as the common cold or influenza.{{cite journal | vauthors = Waldman RH, Ganguly R | title = Therapeutic efficacy of inosiplex (Isoprinosine) in rhinovirus infection | journal = Annals of the New York Academy of Sciences | volume = 284 | issue = 1 | pages = 153–160 | date = March 1977 | pmid = 81636 | doi = 10.1111/j.1749-6632.1977.tb21946.x | bibcode = 1977NYASA.284..153W }} As such, it is commonly prescribed preventatively, albeit at a lower dose. Several studies have investigated the benefits of inosine pranobex therapy in frequently ill children{{Cite journal | vauthors = Gołębiowska-Wawrzyniak M, Markiewicz K, Kozar A, Derentowicz P, Siwińska-Gołębiowska H |date=2004-06-30 |title=The Study on Therapeutic Efficacy of Inosine Pranobex in Children. |url=http://journal.pan.olsztyn.pl/THE-STUDY-ON-THERAPEUTIC-EFFICACY-OF-INOSINE-PRANOBEX-IN-CHILDREN-,98630,0,2.html |journal=Polish Journal of Food and Nutrition Sciences |language=english |volume=54 |issue=2s |pages=33–36 |issn=1230-0322}}{{Cite journal | vauthors = Melekhina E, Muzyka A, Lysenkova M, Gorelov A |date=2018 |title=A comparative analysis of therapeutic regimens in children with monthly respiratory infections and reactivation of infection caused by human herpesvirus type 6 |journal=Voprosy praktičeskoj pediatrii |volume=13 |issue=5 |pages=74–82 |doi=10.20953/1817-7646-2018-5-74-82 |issn=1817-7646}} and returned positive results in both clinical and immunological outcomes.

Inosine pranobex has been suggested as an antiviral for herpesviruses, such as herpes simplex virus types 1 and 2, cytomegalovirus (CMV), and Epstein-Barr virus (EBV),{{cite journal | vauthors = Hashimoto K, Hosoya M | title = Advances in Antiviral Therapy for Subacute Sclerosing Panencephalitis | journal = Molecules | volume = 26 | issue = 2 | page = 427 | date = January 2021 | pmid = 33467470 | pmc = 7830519 | doi = 10.3390/molecules26020427 | doi-access = free }} The drug also proved helpful in managing complicated cases of lengthy reactivations of herpesviruses such as EBV, and subsequent post-viral fatigue.{{citation needed|date=April 2025}}

Inosine pranobex may be prescribed for the treatment of HPV infections both benign and oncogenic,{{Cite web | vauthors = Šimůnková M |title=Inosin pranobex u akutních i chronických virových onemocnění {{!}} MT |url=https://www.tribune.cz/medicina/inosin-pranobex-u-akutnich-i-chronickych-virovych-onemocneni/ |access-date=2024-05-02 |website=www.tribune.cz |language=cs}} as a very safe and effective alternative therapy. Usually it is administered in combination with other treatment methods, such as CO₂ laser and podophyllotoxin.

It was proven to be effective at treating genital warts{{cite journal | vauthors = Davidson-Parker J, Dinsmore W, Khan MH, Hicks DA, Morris CA, Morris DF | title = Immunotherapy of genital warts with inosine pranobex and conventional treatment: double blind placebo controlled study | journal = Genitourinary Medicine | volume = 64 | issue = 6 | pages = 383–386 | date = December 1988 | pmid = 2465265 | pmc = 1194272 | doi = 10.1136/sti.64.6.383 }} in combination with conventional non-surgical treatments. It can also be used to treat vulvar HPV infection, and cervical dysplasia.{{Cite journal | vauthors = Gudz OV, Kamilova IK, Miklin OP |date=2016 |title=HPV infection of the cervix uteri: Prospects for combination treatment |journal=Rossiiskii Vestnik Akushera-ginekologa |volume=16 |issue=2 |page=99 |doi=10.17116/rosakush201616299-103 |issn=1726-6122}} It was also suggested as a possible alternative treatment for young women with chronic vulvodynia.{{cite journal | vauthors = Sand Petersen C, Weismann K | title = Isoprenosine improves symptoms in young females with chronic vulvodynia | journal = Acta Dermato-Venereologica | volume = 76 | issue = 5 | page = 404 | date = September 1996 | pmid = 8891022 | doi = 10.2340/0001555576404404 | doi-access = free }} Several long-term studies have shown efficacy even compared to surgical method at treating oral HPV-positive proliferative verrucous leucoplakia (PVL).{{cite journal | vauthors = Femiano F, Gombos F, Scully C | title = Oral proliferative verrucous leukoplakia (PVL); open trial of surgery compared with combined therapy using surgery and methisoprinol in papillomavirus-related PVL | journal = International Journal of Oral and Maxillofacial Surgery | volume = 30 | issue = 4 | pages = 318–322 | date = August 2001 | pmid = 11518355 | doi = 10.1054/ijom.2001.0066 }}

The evidence in treating rhinovirus infections is mixed. While no statistically significant effect was observed in rhinovirus 44 or 32 infection,{{cite journal | vauthors = Pachuta DM, Togo Y, Hornick RB, Schwartz AR, Tominaga S | title = Evaluation of isoprinosine in experimental human rhinovirus infection | journal = Antimicrobial Agents and Chemotherapy | volume = 5 | issue = 4 | pages = 403–408 | date = April 1974 | pmid = 15825396 | pmc = 428983 | doi = 10.1128/aac.5.4.403 }} its administration in rhinovirus 21 infection led to statistically improved health outcomes in patients, shortened infectivity and decreased viral shedding. In Influenza and Influenza-like (RSV, adenovirus and parainfluenza virus) infections, inosine pranobex did lower the symptom severity and duration.{{cite journal | vauthors = Beran J, Šalapová E, Špajdel M | title = Inosine pranobex is safe and effective for the treatment of subjects with confirmed acute respiratory viral infections: analysis and subgroup analysis from a Phase 4, randomised, placebo-controlled, double-blind study | journal = BMC Infectious Diseases | volume = 16 | issue = 1 | page = 648 | date = November 2016 | pmid = 27821093 | pmc = 5100179 | doi = 10.1186/s12879-016-1965-5 | doi-access = free }}

When the global coronavirus pandemic hit in 2020, inosine pranobex was one of the first medication used experimentally to treat the SARS-CoV-2 induced virosis, mainly due to its remarkably wide area of use and general antiviral properties. Several clinical trials were conducted returning largely positive results.

Its use was pioneered in the Czech Republic, where it was first noted that use greatly decreases mortality among elderly.{{cite journal | vauthors = Beran J, Špajdel M, Slíva J | title = Inosine Pranobex Deserves Attention as a Potential Immunomodulator to Achieve Early Alteration of the COVID-19 Disease Course | journal = Viruses | volume = 13 | issue = 11 | page = 2246 | date = November 2021 | pmid = 34835052 | pmc = 8619495 | doi = 10.3390/v13112246 | doi-access = free }}{{cite journal | vauthors = Beran J, Špajdel M, Katzerová V, Holoušová A, Malyš J, Finger Rousková J, Slíva J | title = Inosine Pranobex Significantly Decreased the Case-Fatality Rate among PCR Positive Elderly with SARS-CoV-2 at Three Nursing Homes in the Czech Republic | journal = Pathogens | volume = 9 | issue = 12 | page = 1055 | date = December 2020 | pmid = 33339426 | pmc = 7766462 | doi = 10.3390/pathogens9121055 | doi-access = free }} In 2022, a large Phase 3 trial concluded that administration of inosine pranobex should start as early as possible with greatly improved outcomes in mild to moderate COVID-19 patients.{{cite journal | vauthors = Jayanthi CR, Swain AK, Ganga RT, Halnor D, Avhad A, Khan MS, Ghosh A, Choudhary SS, Yannawar AN, Despande S, Patel M, Anne KP, Bangar Y | title = Efficacy and Safety of Inosine Pranobex in COVID-19 Patients: A Multicenter Phase 3 Randomized Double-Blind, Placebo-Controlled Trial | journal = Advanced Therapeutics | volume = 5 | issue = 12 | page = 2200159 | date = September 2022 | pmid = 36246300 | pmc = 9539257 | doi = 10.1002/adtp.202200159 }}

In type B viral hepatitis, inosine pranobex was found ineffective during the acute phase of the infection, though in 28 days lower bilirubin and transaminase levels were detected. Greater number of patients became antigen-negative within a 90 day time-frame indicating a faster recovery rate.{{Cite journal | vauthors = Indries M |date=December 2013 |title=Clinical and histological corelations in chronic viral hepatitis C |journal=BMC Infectious Diseases |volume=13 |issue=S1 |pages=52 |doi=10.1186/1471-2334-13-s1-p52 |doi-access=free |issn=1471-2334|pmc=3882649 }}

Type C viral hepatitis was not studied as extensively, hence not so much data is available. It has been shown that inosine pranobex therapy in combination with ribavirin normalizes alanine aminotransferase levels in patients unresponsive to interferon treatment.{{cite journal | vauthors = Pardo M, Carreño V | title = Lack of efficacy of inosine pranobex in the treatment of chronic hepatitis C | journal = Journal of Hepatology | volume = 21 | issue = 2 | page = 278 | date = August 1994 | pmid = 7527438 | doi = 10.1016/s0168-8278(05)80410-6 }}

There is also some evidence of the drug being helpful in treating chronic post-viral fatigue.{{Cite web |title=Největší informační zdroj pro lékaře | trans-title = The largest information source for doctors |url=https://www.prolekare.cz/specialist-agreement |access-date=2024-05-01 |website=www.prolekare.cz |language=cs}} This might be indicative of the drug being effective even for other post-acute infection syndromes (PAIS), such as Long COVID (PASC).{{Cite journal |author=Бабаченко, И. В. |journal=Journal Infectology |date=2024-01-10 |script-title=ru:Эффективность Инозина Пранобекса в лечении и профилактике инфекционных заболеваний (систематический обзор) |url=https://journal.niidi.ru/jofin/article/view/1566 |script-journal=ru:Журнал инфектологии |language=ru |volume=15 |issue=4 |pages=42–53 |doi=10.22625/2072-6732-2023-15-4-42-53 |issn=2072-6732|doi-access=free }} In 2003, the possibility of using inosine pranobex for treating myalgic encephalomyelitis/chronic fatigue syndrome was investigated experimentally and returned promising results,{{Cite journal | vauthors = Diaz-Mitoma F, Turgonyi E, Kumar A, Lim W, Larocque L, Hyde BM |date=January 2003 |title=Clinical Improvement in Chronic Fatigue Syndrome Is Associated with Enhanced Natural Killer Cell-Mediated Cytotoxicity: The Results of a Pilot Study with Isoprinosine |journal=Journal of Chronic Fatigue Syndrome |language=en |volume=11 |issue=2 |pages=71–95 |doi=10.1300/J092v11n02_06 |issn=1057-3321}} when 6 out of 10 subjects reported noticeable improvement. Promised large scale Phase II/III clinical trials confirming initially observed effects have not been conducted yet as of 2024.

In 2021, the US ME/CFS Clinician Coalition recommended the use of inosine pranobex for "immune dysfunction" symptoms, specifically "frequent viral infections, herpes simplex outbreaks, low natural killer cell activity, sore throat, tender nodes, low grade fevers".{{cite book | vauthors = Campling F, Sharpe M | chapter = Some myths about CFS/ME |date=2008-07-03 | title = Chronic fatigue syndrome (CFS/ME) |pages=57–60 |publisher=Oxford University PressOxford |isbn=978-0-19-923316-8 |doi=10.1093/oso/9780199233168.003.0009 }}

Although the effect is unclear, several case reports have suggested that inosine pranobex may provide beneficial therapeutic effects in managing subacute sclerosing panencephalitis. Several long-term studies suggested that the drug both increased survival and decreased neurological deficiencies.{{cite journal | vauthors = Huttenlocher PR, Mattson RH | title = Isoprinosine in subacute sclerosing panencephalitis | journal = Neurology | volume = 29 | issue = 6 | pages = 763–771 | date = June 1979 | pmid = 88024 | doi = 10.1212/WNL.29.6.763 }}{{additional citations needed|date=April 2025}} It is not a cure for the illness though, as currently no cure exists.

Inosine pranobex has been suggested to delay AIDS progression in HIV-positive patients.{{cite journal | vauthors = Glasky AJ, Gordon JF | title = Isoprinosine (inosine pranobex BAN, INPX) in the treatment of AIDS and other acquired immunodeficiencies of clinical importance | journal = Cancer Detection and Prevention. Supplement | volume = 1 | pages = 597–609 | date = 1987-01-01 | pmid = 2446760 }}{{cite journal | vauthors = De Simone C, Famularo G, Tzantzoglou S, Moretti S, Jirillo E | title = Inosine pranobex in the treatment of HIV infection: a review | journal = International Journal of Immunopharmacology | volume = 13 | issue = Suppl 1 | pages = 19–27 | date = January 1991 | pmid = 1726683 | doi = 10.1016/0192-0561(91)90120-v }} In a phase I study of 831 HIV-positive patients conducted during the early phase of the HIV pandemic, prior to entry into clinical use of disease-specific and effective antiretroviral medications,{{cite web|url=https://www.acs.org/education/whatischemistry/landmarks/highly-active-antiretroviral-therapy-hiv.html|title=Discovery of Highly Active Antiretroviral Therapy for HIV|website=American Chemical Society|access-date=22 April 2025|last=Levy|first=Max}} inosine pranobex administration was found to be safe with no serious side effects reported.

For acute infection, the typical dose is 50 mg/day/kg of body weight. For prevention of chronic issues lower doses are typically recommended, usually under 2 g/day. The maximum dose permitted is around 4 g/day. The toxicity of the drug in humans is unknown, but doses upward of 1 g/kg of body weight were toxic in rodents.

The most commonly found effects are nausea and vomiting. Hypotension, drowsiness and skin irritation may also occur. Metabolism of the inosine component of the drug can lead to an increase in uric acid levels in both blood and urine. The occurrence of transient reversible hyperuricaemia occurs in about 10% of patients taking inosine pranobex.{{cite journal | vauthors = You Y, Wang L, Li Y, Wang Q, Cao S, Tu Y, Li S, Bai L, Lu J, Wei Z, Chen W, Hao F | title = Multicenter randomized study of inosine pranobex versus acyclovir in the treatment of recurrent herpes labialis and recurrent herpes genitalis in Chinese patients | journal = The Journal of Dermatology | volume = 42 | issue = 6 | pages = 596–601 | date = June 2015 | pmid = 25819042 | doi = 10.1111/1346-8138.12845 }} Due to the potential risk of hyperuricosuria and the development of urate nephrolithiasis, increased fluid intake and exclusion of acidic foods is recommended during isoprinosine therapy. Its administration is not recommended in combination with immunosuppressing medicine.

Tolerance studies in healthy individuals and patients have consistently shown that inosine pranobex has no serious side effects and is remarkably well tolerated by the organism. Continuous administration of the drug for up to 7 years, at doses ranging from 1 to 8 g per day, has only occasionally caused transient nausea. This nausea was associated with a large number of tablets ingested. In addition, transient increases in serum and urinary uric acid levels have been reported. This increase in serum uric acid concentration is more common in male patients than in females.{{cite journal | vauthors = Campoli-Richards DM, Sorkin EM, Heel RC | title = Inosine pranobex. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy | journal = Drugs | volume = 32 | issue = 5 | pages = 383–424 | date = November 1986 | pmid = 2431857 | doi = 10.2165/00003495-198632050-00001 }}

Neither long-term damage not death from overdose have been reported in relation to inosine pranobex, doses upward of 1 g/kg of body weight were found to be toxic in rodents.{{Cite web |title=Inosine pranobex |url=https://go.drugbank.com/drugs/DB13156 |access-date=2024-05-02 |website=go.drugbank.com |language=en}} The drug is metabolized very quickly, therefore any side effects should subside quickly with no long-term effects.

The first studies conducted with the drug happened as early as the 1970s. It was licensed in 1971{{cite journal | vauthors = Beran J, Špajdel M, Slíva J | title = Inosine Pranobex Deserves Attention as a Potential Immunomodulator to Achieve Early Alteration of the COVID-19 Disease Course | journal = Viruses | volume = 13 | issue = 11 | page = 2246 | date = November 2021 | pmid = 34835052 | pmc = 8619495 | doi = 10.3390/v13112246 | doi-access = free }} with the first robust preliminary review of its efficacy having been published in 1986.{{cite journal | vauthors = Campoli-Richards DM, Sorkin EM, Heel RC | title = Inosine pranobex. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy | journal = Drugs | volume = 32 | issue = 5 | pages = 383–424 | date = November 1986 | pmid = 2431857 | doi = 10.2165/00003495-198632050-00001 }} Since the beginning, the drug was praised for its wide array of use cases, it was noted early on that it has a clinically noticeable effect on the immune function. In the 1990s, the possibility of the drug being used for HIV infection was also been investigated, with the results suggesting improved immune function. Nonetheless, following the development of more effective HIV drugs, this use case has been largely discontinued.

Throughout the 21st century, inosine pranobex has been used mainly in Central and Eastern Europe, in contrast to the United States, where the medication is not as widely available. In Eastern Europe, namely Poland, the medication is available over-the-counter under the brand name of Groprinosin® thanks to its safety and low risk of overdose.

In 2020, inosine pranobex was found to be a cheap and effective treatment for SARS-CoV-2 in cases not requiring hospitalization with fatality rate effectively halved as a result of its use.

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Category:Antiviral drugs