Tizanidine, sold under the brand name Zanaflex among others, is a medication that is used to treat

muscle spasticity Spasticity () is a feature of altered skeletal muscle performance with a combination of paralysis, increased tendon reflex activity, and hypertonia. It is also colloquially referred to as an unusual "tightness", stiffness, or "pull" of muscles ...

due to

spinal cord injury A spinal cord injury (SCI) is damage to the spinal cord that causes temporary or permanent changes in its function. Symptoms may include loss of muscle function, sensation, or autonomic function in the parts of the body served by the spinal cor ...

multiple sclerosis Multiple (cerebral) sclerosis (MS), also known as encephalomyelitis disseminata or disseminated sclerosis, is the most common demyelinating disease, in which the insulating covers of nerve cells in the brain and spinal cord are damaged. This ...

as well as

spastic cerebral palsy Spastic cerebral palsy is the type of cerebral palsy characterized by spasticity or high muscle tone often resulting in stiff, jerky movements. Cases of spastic CP are further classified according to the part or parts of the body that are most af ...

. Effectiveness appears similar to baclofen or

diazepam Diazepam, first marketed as Valium, is a medicine of the benzodiazepine family that acts as an anxiolytic. It is commonly used to treat a range of conditions, including anxiety, seizures, alcohol withdrawal syndrome, muscle spasms, insomnia, ...

. It is taken by mouth. Common side effects of Tizanidine include dry mouth, sleepiness,

weakness Weakness is a symptom of a number of different conditions. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, i ...

, and

dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness. Dizziness is a common medical c ...

. Serious side effects may include low blood pressure, liver problems,

psychosis Psychosis is a condition of the mind that results in difficulties determining what is real and what is not real. Symptoms may include delusions and hallucinations, among other features. Additional symptoms are incoherent speech and behavi ...

, and

QT prolongation Long QT syndrome (LQTS) is a condition affecting repolarization (relaxing) of the heart after a heartbeat, giving rise to an abnormally lengthy QT interval. It results in an increased risk of an irregular heartbeat which can result in fainting, ...

. It is unclear if use in

pregnancy Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ...

and

breastfeeding Breastfeeding, or nursing, is the process by which human breast milk is fed to a child. Breast milk may be from the breast, or may be expressed by hand or pumped and fed to the infant. The World Health Organization (WHO) recommends that bre ...

is safe. It is an α2-adrenergic agonist and how it works is not entirely clear. Tizanidine was approved for medical use in the United States in 1996. It is available as a

generic medication A generic drug is a pharmaceutical drug that contains the same chemical substance as a drug that was originally protected by chemical patents. Generic drugs are allowed for sale after the patents on the original drugs expire. Because the active ...

. In 2020, it was the 84th most commonly prescribed medication in the United States, with more than 8million prescriptions.

Medical uses

Tizanidine has been found to be as effective as other

antispasmodic An antispasmodic (synonym: spasmolytic) is a pharmaceutical drug or other agent that suppresses muscle spasms. Smooth muscle spasm One type of antispasmodics is used for smooth muscle relaxation, especially in tubular organs of the gastrointest ...

drugs and is more tolerable than baclofen and

Side effects

Side effects include dizziness, drowsiness, weakness, nervousness, confusion,

hallucinations A hallucination is a perception in the absence of an external stimulus that has the qualities of a real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. Hallucination is a combinati ...

, strange dreams, depression, vomiting, dry mouth, constipation, diarrhea, stomach pain, heartburn, increased muscle spasms, back pain, rash, sweating, and a tingling sensation in the arms, legs, hands, and feet.

Interactions

Concomitant Concomitance is the condition of accompanying or coexisting. A concomitant is something that accompanies something else. Concomitant or concomitance may refer to: * Concomitance (doctrine), a Christian doctrine * Concomitant (classical algebraic ...

use of tizanidine and moderate or potent CYP1A2 inhibitors (such as zileuton, certain antiarrhythmics (

amiodarone Amiodarone is an antiarrhythmic medication used to treat and prevent a number of types of cardiac dysrhythmias. This includes ventricular tachycardia (VT), ventricular fibrillation (VF), and wide complex tachycardia, as well as atrial fibril ...

, mexiletine,

propafenone Propafenone, sold under the brand name Rythmol among others, is a class 1c anti-arrhythmic medication, which is used to treat illnesses associated with rapid heart beat such as atrial and ventricular arrhythmias. Mechanism of action Propafen ...

, verapamil),

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 r ...

, famotidine,

aciclovir Aciclovir (ACV), also known as acyclovir, is an antiviral medication. It is primarily used for the treatment of herpes simplex virus infections, chickenpox, and shingles. Other uses include prevention of cytomegalovirus infections following tra ...

, ticlopidine and

oral contraceptives Oral contraceptives, abbreviated OCPs, also known as birth control pills, are medications taken by mouth for the purpose of birth control. Female Two types of female oral contraceptive pill, taken once per day, are widely available: * The combi ...

) is contraindicated. Concomitant use of tizanidine with fluvoxamine, a potent CYP1A2 inhibitor in humans, resulted in a 33-fold increase in the tizanidine AUC (plasma drug concentration-time curve). For this reason both fluvoxamine and tizanidine should not be taken at the same time. Fluoroquinolone antibiotics such as

moxifloxacin Moxifloxacin is an antibiotic, used to treat bacterial infections, including pneumonia, conjunctivitis, endocarditis, tuberculosis, and sinusitis. It can be given by mouth, by injection into a vein, and as an eye drop. Common side effects ...

levofloxacin Levofloxacin, sold under the brand name Levaquin among others, is an antibiotic medication. It is used to treat a number of bacterial infections including acute bacterial sinusitis, pneumonia, H. pylori (in combination with other medications), ...

, and

ciprofloxacin Ciprofloxacin is a fluoroquinolone antibiotic used to treat a number of bacterial infections. This includes bone and joint infections, intra abdominal infections, certain types of infectious diarrhea, respiratory tract infections, skin i ...

should also be avoided due to an increased serum concentration of tizanidine when administered concomitantly. Tizanidine has the potential to interact with other central nervous system depressants. Alcohol should be avoided, particularly as it can upset the stomach. The CNS-depressant effects of tizanidine and alcohol are additive. Caution with the following

interactions Interaction is action that occurs between two or more objects, with broad use in philosophy and the sciences. It may refer to: Science * Interaction hypothesis, a theory of second language acquisition * Interaction (statistics) * Interactions ...

: * antibiotics such as

enoxacin EnoxacinEnoxacin is sold under the following trade names: Almitil, Bactidan, Bactidron, Comprecin, Enoksetin, Enoxen, Enroxil, Enoxin, Enoxor, Flumark, Penetrex, Gyramid, Vinone. is an oral broad-spectrum fluoroquinolone antibacterial agent used in ...

gatifloxacin Gatifloxacin (brand names Gatiflo, Tequin, and Zymar) is an antibiotic of the fourth-generation fluoroquinolone family, that like other members of that family, inhibits the bacterial enzymes DNA gyrase and topoisomerase IV. It was patented i ...

, lomefloxacin,

, ofloxacin,

sparfloxacin Sparfloxacin is a fluoroquinolone antibiotic used in the treatment of bacterial infections. It has a controversial safety profile. It was patented in 1985 and approved for medical use in 1993. Zagam is no longer available in the United States. ...

, trovafloxacin, or norfloxacin; * blood pressure medications such as

clonidine Clonidine, sold under the brand name Catapres among others, is an α2-adrenergic agonist medication used to treat high blood pressure, ADHD, drug withdrawal ( alcohol, opioids, or nicotine), menopausal flushing, diarrhea, spasticity, and c ...

, guanabenz, guanfacine (Tenex), or

methyldopa Methyldopa, sold under the brand name Aldomet among others, is a medication used for high blood pressure. It is one of the preferred treatments for high blood pressure in pregnancy. For other types of high blood pressure including very high bl ...

; * heart rhythm medications such as

(Cordarone, Pacerone), mexiletine (Mexitil),

(Rhythmol), and verapamil (Calan, Covera, Isoptin).

Pharmacology

Tizanidine is an α₂ receptor agonist closely related to

. It has approximately one tenth to one fifteenth of the pressure lowering effect of clonidine. The relation between the α₂ receptor agonism and the spasmolytic action is still not fully understood.

Route of administration

Tizanidine is available as a tablet or capsule. Capsules may be opened and sprinkled on food. However, this may change the absorption of the medication compared to taking the capsule whole.

Chemistry

It has a

volume of distribution In pharmacology, the volume of distribution (VD, also known as apparent volume of distribution, literally, ''volume of dilution'') is the theoretical volume that would be necessary to contain the total amount of an administered drug at the same c ...

of 2.4 L/kg following intravenous administration.

References

External links

* * * {{Authority control Muscle relaxants Alpha-2 adrenergic receptor agonists Imidazolines Novartis brands Organochlorides Benzothiadiazoles Wikipedia medicine articles ready to translate