Tizanidine

Tizanidine works in the spinal cord as an alpha-2 adrenergic agonist, reducing the nerve signals that keep muscles in a state of excessive tone. The UK SmPC for Tizagelan tablets lists two groups of indications. The first is painful spasm of the skeletal muscles linked to cervical and lumbar spine problems or following surgery such as a slipped disc operation or hip joint procedures. The second is spasticity due to neurological disease, including multiple sclerosis, chronic myelopathy, degenerative spinal cord disease, stroke and cerebral palsy.

This listing is for tizanidine 2 mg tablets, available in packs of 30, 60, 90, 120, 180 or 360 tablets. These are imported generic tablets that are not covered by a UK licence, so the packaging will differ from British packs.

Because tizanidine has a narrow therapeutic index and blood levels differ a great deal from one person to another, the dose is tailored individually. For muscle spasm, the SmPC suggests 2 to 4 mg three times daily, with an extra 2 to 4 mg late in the evening in severe cases to make use of the sedative effect. For spasticity, the starting total should not exceed 6 mg a day in three divided doses, rising in steps of 2 to 4 mg every three or four days to a week. Most people respond to 12 to 24 mg daily split into three or four doses, and the daily total must not exceed 36 mg. When kidney function is markedly reduced (creatinine clearance below 25 ml/min), treatment begins at 2 mg once a day. Older adults also start low and increase in small steps.

Tizanidine is a prescription-only medicine in the UK. Generic tablets are licensed, for example Tizagelan 2 mg and 4 mg tablets from G.L. Pharma, whose SmPC and patient leaflet are on the electronic medicines compendium. It is not recommended for anyone under 18.

Tizanidine must not be used in severe liver impairment or together with fluvoxamine or ciprofloxacin, which raise its blood levels by roughly ten- to thirty-three-fold. Other CYP1A2 inhibitors, such as amiodarone, mexiletine, propafenone, verapamil, cimetidine, famotidine, aciclovir and some quinolone antibiotics, are best avoided, and combined hormonal contraceptives can increase levels moderately. Liver function should be checked monthly for the first four months in anyone taking 12 mg or more a day, or sooner if unexplained nausea, loss of appetite or tiredness appear. Blood pressure medicines, beta-blockers and digoxin may add to low blood pressure or a slow pulse, while alcohol, benzodiazepines, opioids and other sedatives deepen drowsiness. Smoking lowers its blood levels. Stopping suddenly after high doses can cause rebound high blood pressure and a racing heart, so the dose is reduced gradually, by 2 to 4 mg per day.

Many side effects depend on the dose and lessen with slow titration. Sleepiness, tiredness, dizziness, dry mouth, lower blood pressure, nausea and stomach upset are typical, and liver enzymes may rise. Hallucinations, a slow heart rate and fainting on standing up are less frequent; serious allergic reactions are possible. Hepatitis and liver failure have been reported, so yellowing of the skin or eyes, dark urine or persistent sickness should be checked promptly. Drowsiness can affect driving. The decision to prescribe tizanidine, and at what dose, lies with your doctor.