Rimantadine (

INN Inns are generally establishments or buildings where travelers can seek lodging, and usually, food and drink. Inns are typically located in the country or along a highway; before the advent of motorized transportation they also provided accommo ...

, sold under the trade name '
Flumadine
'') is an orally administered

antiviral drug Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Unlike most antibiotics, antiviral drugs do n ...

used to treat, and in rare cases prevent,

influenzavirus A '' A virus'' (''IAV'') causes influenza in birds and some mammals, and is the only species of the genus ''Alphainfluenzavirus'' of the virus family '' Orthomyxoviridae''. Strains of all subtypes of influenza A virus have been isolated from wi ...

infection. When taken within one to two days of developing symptoms, rimantadine can shorten the duration and moderate the severity of influenza. Rimantadine can mitigate symptoms, including fever. Both rimantadine and the similar drug

amantadine Amantadine, sold under the brand name Gocovri among others, is a medication used to treat dyskinesia associated with parkinsonism and influenza caused by type A influenzavirus, though its use for the latter is no longer recommended due to wid ...

are derivates of

adamantane Adamantane is an organic compound with a formula C10H16 or, more descriptively, (CH)4(CH2)6. Adamantane molecules can be described as the fusion of three cyclohexane rings. The molecule is both rigid and virtually stress-free. Adamantane is the m ...

. Rimantadine is found to be more effective than amantadine because when used the patient displays fewer symptoms. Rimantadine was approved by the

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...

(FDA) in 1994. Rimantadine was approved for medical use in 1993. Seasonal H3N2 and 2009 pandemic flu samples tested have shown resistance to rimantadine, and it is no longer recommended to prescribe for treatment of the flu.

Medical use

Influenza A

Rimantadine inhibits influenza activity by binding to

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

s in the M2 transmembrane channel and blocking proton transport across the M2 channel. Rimantadine is believed to inhibit influenza's

viral replication Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome an ...

, possibly by preventing the uncoating of the virus's protective shells, which are the envelope and capsid. The M2 channel is known to be responsible for viral replication in the influenza virus. Genetic studies suggest that the virus

M2 protein The Matrix-2 (M2) protein is a proton-selective viroporin, integral in the viral envelope of the influenza A virus. The channel itself is a homotetramer (consists of four identical M2 units), where the units are helices stabilized by two disulfi ...

, an

ion channel Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of io ...

specified by virion M2

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

, plays an important role in the susceptibility of influenza A virus to inhibition by rimantadine. Rimantadine is bound inside the pore to amantadine specific amino acid binding sites with hydrogen binding and van der Waals interactions. The ammonium group (with neighboring water molecules) is positioned towards the C terminus with the amantadane group is positioned towards the N-terminus when bound inside the M2 pore. Rimantadine S31N Mutation Binding

Influenza resistance

Resistance to rimantadine can occur as a result of amino acid substitutions at certain locations in the transmembrane region of M2. This prevents binding of the antiviral to the channel. The mutation S31N binding site with rimantadine is shown in the image to the left. It shows rimantadine binding into lumenal (top) or peripheral (bottom) binding sites with influenza M2 channel Serine 31 (gold) or Asparagine 31 (blue).

Rimantadine enantiomers interactions with M2

Rimantadine, when sold as flumadine, is present as a

racemic In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. ...

mixture; the R and S states are both present in the drug. Solid state

NMR Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with ...

studies have shown that the R

enantiomer In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical ant ...

has a stronger binding affinity to the M2 channel pore than the S-enantiomer of rimantadine. Antiviral assay and

electrophysiology Electrophysiology (from Greek , ''ēlektron'', "amber" etymology of "electron"">Electron#Etymology">etymology of "electron" , ''physis'', "nature, origin"; and , '' -logia'') is the branch of physiology that studies the electrical properties of b ...

studies show that there is no significant difference between the R and S enantiomers in binding affinity to amino acids in the M2 channel. Since the enantiomers have similar binding affinity, they also have similar ability to block the channel pore and work as an effective antiviral. Rimantadine enantiomers R and S are pictured interacting with the M2 pore below to the right. This image shows that there is not a significant modeled difference between the R and S enantiomers.

Parkinson's disease

Rimantadine, like its antiviral cousin

, possesses some NMDA antagonistic properties and is used as an antiparkinsonic drug (i.e., in the treatment of

Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...

). However, in general, neither rimantadine nor amantadine is a preferred agent for this therapy and would be reserved for cases of the disease that are less responsive to front-line treatments.

Other

Rimantadine is shown to be effective against other RNA-containing viruses. It can treat

arbovirus Arbovirus is an informal name for any virus that is transmitted by arthropod vectors. The term ''arbovirus'' is a portmanteau word (''ar''thropod-''bo''rne ''virus''). ''Tibovirus'' (''ti''ck-''bo''rne ''virus'') is sometimes used to more spe ...

es like

Saint Louis encephalitis Saint Louis encephalitis is a disease caused by the mosquito-borne Saint Louis encephalitis virus. Saint Louis encephalitis virus is related to Japanese encephalitis virus and is a member of the family ''Flaviviridae''. This disease mainly affe ...

and Sindbis. Other viruses that can be treated with Rimantadine include respiratory synctial and parainfluenza viruses. Rimantadine has also been shown to treat chronic

hepatitis C Hepatitis C is an infectious disease caused by the hepatitis C virus (HCV) that primarily affects the liver; it is a type of viral hepatitis. During the initial infection people often have mild or no symptoms. Occasionally a fever, dark urine, a ...

Drug interactions

* Taking

paracetamol Paracetamol, also known as acetaminophen, is a medication used to treat fever and mild to moderate pain. Common brand names include Tylenol and Panadol. At a standard dose, paracetamol only slightly decreases body temperature; it is inferior ...

(acetaminophen, Tylenol) or

acetylsalicylic acid Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat inc ...

(aspirin) while taking rimantadine is known to reduce the body's uptake of rimantadine by approximately 12%. *

Cimetidine Cimetidine, sold under the brand name Tagamet among others, is a histamine H2 receptor antagonist that inhibits stomach acid production. It is mainly used in the treatment of heartburn and peptic ulcers. The development of longer-acting H2 rec ...

also affects the body's uptake of rimantadine. * Taking anticholigenic drugs with amantadine may increase underlying seizure disorders and aggravate congestive heart failure.

Side effects

Rimantadine can produce

gastrointestinal The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...

and

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...

adverse effects An adverse effect is an undesired harmful effect resulting from a medication or other intervention, such as surgery. An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. The term complica ...

. Approximately 6% of patients (compared to 4% of patients taking a placebo) reported side-effects at a dosage of 200 mg/d. Common side effects include: *

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...

* upset stomach *

nervousness Nervous may refer to: * nervousness * Nervous system, a network of cells in an animal's body that coordinates movement and the senses ** Nervous tissue, the cells of the nervous system that work in aggregate to transmit signals Music * "Nervous" ...

* tiredness *

lightheadedness Lightheadedness is a common and typically unpleasant sensation of dizziness or a feeling that one may faint. The sensation of lightheadedness can be short-lived, prolonged, or, rarely, recurring. In addition to dizziness, the individual may feel ...

* trouble sleeping (

insomnia Insomnia, also known as sleeplessness, is a sleep disorder in which people have trouble sleeping. They may have difficulty falling asleep, or staying asleep as long as desired. Insomnia is typically followed by daytime sleepiness, low energy, ...

) * difficulty concentrating * confusion *

anxiety Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different than fear in that the former is defined as the anticipation of a future threat wh ...

Rimantadine shows fewer CNS symptoms than its sister drug Amantadine. Rimantadine synthesis 1

Synthesis

1-carboxyadamatanones are reduced with sodium borohydride to create racemic hydroxy acid. Excess methyllithium is then added to create methyl ketones which when reduced with lithium aluminum hydride gives the amine group. The synthesis pictured to the left is a synthesis of rimantadine as synthesized in Europe

History

Rimantadine was discovered in 1963 and patented in 1965 in the US by William W. Prichard in Du Pont & Co.,

Wilmington, Delaware Wilmington ( Lenape: ''Paxahakink /'' ''Pakehakink)'' is the largest city in the U.S. state of Delaware. The city was built on the site of Fort Christina, the first Swedish settlement in North America. It lies at the confluence of the Christina ...

(patent on new chemical compound , 1965 and on the first method of synthesis , 1967). Prichard's methods of synthesis of rimantadine from the corresponding ketone oxime were based on its reduction with lithium aluminum hydride.

Synonyms

1-(1-Adamantyl)ethanamine, 1-(Adamantan-1-yl)ethanamine, 1-(adamantan-1-yl)ethan-1-aminem, alpha-Methyl-1-adamantanemethylamine, alpha-Methyladamantanemethylamine, Rimantadine NN:BAN Rimantadinum NN-Latin 1-(1-Adamantyl)ethylamin, Remantadine, Rimantadina NN-Spanish 1-Adamantan-1-yl-ethylamine, RIMANTADIN, HSDB 7438, CHEMBL959, BRN 2715740, 1-Adamantanemethylamine, .alpha.-methyl-, .alpha.-Methyladamantanemethylamine, 1-(1-adamantyl)-ethylamine, 1-(tricyclo .3.1.1~3,7~ec-1-yl)ethanamine, Riamantadine, Rimantadina, Rimantadinum, Tricyclo(3.3.1.13,7)decane-1-methanamine, alpha-methyl-, -(1-adamantyl)ethylmine hydrochloride, Tricyclo(3.3.1.1(sup 3,7))decane-1-methanamine, alpha-methyl-, 1-ADAMANTANEMETHYLAMINE, alpha-METHYL-, 1-Rimantadine, 887336-05-2, Tricyclo .3.1.13,7ecane-1-methanamine, a-methyl-, Rimant, 1-(1-adamantyl)ethylamine, Rimantadine (INN), Enamine_005755, NCGC00159491-02, Rimant & .alpha. IFN, Rimantadine (Flumadine), Rimantidine & .alpha.IFN, 1-Adamantan-1-ylethylamine, rimantidin, Rimantadin A, (R)-1-(Adamantan-1-yl)ethan-1-amine, 1-adamantanylethylamine, Maybridge1_002066, SCHEMBL2981, 1-tricyclo .3.1.1~3,7~ec-1-ylethanamine, Oprea1_602732, SCHEMBL2619249, CHEMBL1201272, DTXSID2023561, SCHEMBL20409367, CHEBI:94440, CTK6A4437, HMS1410F13, HMS2090L19, HMS3604N13, HMS3655J05, 1-Adamantanemethylamine, ?-methyl-, ALBB-013870, BCP12269, HY-B0338, ZX-AN012619, ANW-72018, BBL013215, BDBM50216627, MFCD00869344, s1964, STK177253, (alpha-methyl-1-adamantyl)methylamine, AKOS000264537, AKOS006238592, AKOS016038537, .alpha.-Methyl-1-adamantanemethylamine, AM84461, API0024288, BBV-156986, CCG-236078, CS-2380, DB00478, FCH3207896, MCULE-9027470290, IDI1_007990, NCGC00159491-03, NCGC00159491-05, AK-58175, AS-68744, CC-34261, LS-15019, OR315791, SBI-0206810.P001, AB0012750, AX8049536, DB-042207, FT-0630403, H6325, ST45025920, SW220023-1, EN300-33990, C07236, D08483, Q421711- 3R,5S,7s)-adamantan-1-ylthan-1-amine, AB00638368-09, AB00959689-03, AB01506092_02, AB01506092_03, 392R284, C-06592, BRD-A84282119-003-01-2, Z56757137, 1-(Tricyclo .3.1.1>3,7>ec-1-yl)ethanamine (HCl), Tricyclo(3.3.1.1^3,7)decane-1-methanamine, .alpha.-methyl-, 1-(1-Adamantyl)ethylamine Hydrochloride;Rimantadine hydrochloride, Tricyclo(3.3.1.1(sup 3,7))decane-1-methanamine, .alpha.-methyl-, Tricyclo ,3,1,1(3,7)ecane-1-methanamine, .alpha.-methyl-, Tricyclo(3.3.1.1^3,7)decane-1-methanamine, .alpha.-methyl- & IFN.alpha

References

External links

U.S. FDA press release announcing rimantadine's approval

* ttps://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a698029.html U.S. NIH rimantadine description
U.S. CDC flu anti-viral treatment information
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