The pill debossed with the imprint 1105 is Tizanidine Hydrochloride (4 mg). It is a prescription-only skeletal muscle relaxant used primarily to manage muscle spasticity, which involves temporary rigidity, tension, and cramping. This particular variation of the pill is manufactured by Viona Pharmaceuticals.
Pill Identification
If you are physically verifying this medication, look for the following characteristics:
- Imprint: “1105” on one side.
- Color: White to off-white.
- Shape: Round.
- Score Lines: The reverse side features a quadrisecting score mark (two intersecting perpendicular lines), which divides the tablet into four equal segments, allowing it to be split into smaller 1 mg increments if directed by a provider.
- Strength: 4 mg of Tizanidine active ingredient.
Mechanism of Action: How it Works
Unlike some muscle relaxants that act directly on muscle tissue, Tizanidine works entirely within the central nervous system (CNS)—specifically in the brain and spinal cord.
It acts as a central alpha-2 adrenergic receptor agonist.
- When Tizanidine binds to these alpha-2 receptors on the nerves, it slows down the firing of motor neurons.
- This reduces the release of excitatory amino acids (like glutamate and aspartate) that normally signal a muscle to contract or spasm.
- By dampening these overactive spinal signals, Tizanidine decreases muscle tone and spasticity without significantly reducing overall muscle strength.
Indications & Administration Dosages
Tizanidine is approved for the management of spasticity resulting from conditions such as multiple sclerosis (MS), spinal cord injuries, stroke, or traumatic brain injury.
Because it has a very short therapeutic window meaning its effects peak quickly and wear off rapidly dosing is carefully tailored to a patient’s active daily schedule.
- Starting Dose: Typically 2 mg to 4 mg taken orally.
- Frequency: Can be repeated every 6 to 8 hours as needed, up to a maximum of 3 doses in a 24-hour period.
- Maximum Limit: The total daily dose should never exceed 36 mg.
- The Food Consistency Rule: Tizanidine interacts uniquely with food. Taking it with meals increases how fast and how much of the drug your body absorbs compared to taking it on an empty stomach. Because changing back and forth can cause unexpected side effects or reduce how well the drug works, you must choose one method—always take it with food OR always take it on an empty stomach and stay consistent.
Side Effects
Tizanidine has a prominent sedative profile due to its impact on the central nervous system.
Common Side Effects
- Somnolence: Extreme drowsiness or sleepiness.
- Dry Mouth (Xerostomia): Highly common; can often be managed by sipping water or chewing sugarless gum.
- Asthenia: General muscle weakness or lack of energy.
- Dizziness: Feeling lightheaded, especially when moving around.
- Constipation and Vomiting: Gastrointestinal slowing.
Serious Side Effects (Require Immediate Medical Care)
- Hallucinations or Delusions: Seeing or hearing things that are not there (occurs in roughly 3% of patients in clinical trials).
- Severe Bradycardia: A dangerously slow heart rate.
- Fainting (Syncope): Complete loss of consciousness due to rapid blood pressure drops.
Critical Warnings & Precautions
Dangerous Drug Interactions (Contraindications)
Tizanidine must never be taken with strong CYP1A2 inhibitors, such as the antibiotic ciprofloxacin (Cipro) or the antidepressant fluvoxamine (Luvox). The CYP1A2 enzyme in your liver is responsible for breaking down Tizanidine. Blocking this enzyme can cause Tizanidine levels in your blood to skyrocket by over 300%, leading to profound sedation, severe low blood pressure, and collapse.
Major Warnings
- Hypotension (Low Blood Pressure): Tizanidine is chemically related to the blood pressure drug clonidine. It can cause significant drops in blood pressure, leading to dizziness or orthostatic hypotension (dizziness when standing up quickly). Caution is required if you are already taking blood pressure medications.
- Risk of Liver Injury: Tizanidine can cause liver toxicity. Healthcare providers typically monitor liver function tests (specifically aminotransferase/ALT levels) before starting treatment and monthly for the first few months. Inform your doctor immediately if you experience unexplained nausea, fatigue, dark urine, or yellowing of the skin/eyes (jaundice).
- Do Not Stop Suddenly (Withdrawal Risk): If you have been taking high doses of Tizanidine for a long period, stopping abruptly can trigger withdrawal symptoms. These include a dangerous rebound spike in blood pressure (hypertension), a racing heart rate (tachycardia), and severe muscle tightness. Doses must be tapered down slowly under medical supervision.
- CNS Depressant Additive Effects: Alcohol, prescription painkillers, or sleeping aids will amplify Tizanidine’s sedative properties. Avoid driving or operating complex machinery until you know exactly how this medication impacts your alertness.