tizanidine 0.4 MG/ML Oral Solution [Ontralfy]

INDICATIONS AND USAGE Tizanidine Tablets, USP is a central alpha-2-adrenergic agonist indicated for the management of spasticity. Because of the short duration of therapeutic effect, treatment with Tizanidine Tablets, USP should be reserved for those daily activities and times when relief of spasticity is most important [see Dosage and Administration(2.1) ]. Tizanidine Tablets, USP is a central alpha-2-adrenergic agonist indicated for the management of spasticity. Because of the short duration of therapeutic effect, treatment with Tizanidine Tablets, USP should be reserved for those daily activities and times when relief of spasticity is most important [ see Dosage and Administration (1) ].

DOSAGE & ADMINISTRATION 2.1 Dosing Information Tizanidine Tablets, USP tablets may be prescribed with or without food. Once the formulation has been selected and the decision to take with or without food has been made, this regimen should not be altered. Food has complex effects on tizanidine pharmacokinetics, which differ with the different formulations. Tizanidine Capsules and Tizanidine Tablets, USP are bioequivalent to each other under fasting conditions (more than 3 hours after a meal), but not under fed conditions (within 30 minutes of a meal). These pharmacokinetic differences may result in clinically significant differences when switching administration of tablet and capsules and when switching administration between the fed or fasted state. These changes may result in increased adverse events, or delayed or more rapid onset of activity, depending upon the nature of the switch. For this reason, the prescriber should be thoroughly familiar with the changes in kinetics associated with these different conditions [ see Clinical Pharmacology ( 12.3 ) ]. The recommended starting dose is 2 mg. Because the effect of Tizanidine Tablets, USP peaks at approximately 1 to 2 hours post-dose and dissipates between 3 to 6 hours post-dose, treatment can be repeated at 6 to 8 hour intervals, as needed, to a maximum of three doses in 24 hours. Dosage can be gradually increased by 2 mg to 4 mg at each dose, with 1 to 4 days between dosage increases, until a satisfactory reduction of muscle tone is achieved. The total daily dose should not exceed 36 mg. Single doses greater than 16 mg have not been studied. 2.2 Dosing in Patients with Renal Impairment Tizanidine Tablets, USP should be used with caution in patients with renal insufficiency (creatinine clearance < 25 mL/min), as clearance is reduced by more than 50%. In these patients, during titration, the individual doses should be reduced. If higher doses are required, individual doses rather than dosing frequency should be increased [ see Warnings and Precautions ( Error! Hyperlink reference not valid. ) ]. 2.3 Dosing in Patients with Hepatic Impairment Tizanidine Tablets, USP should be used with caution in patients with any hepatic impairment. In these patients, during titration, the individual doses should be reduced. If higher doses are required, individual doses rather than dosing frequency should be increased. Monitoring of aminotransferase levels is recommended for baseline and 1 month after maximum dose is achieved, or if hepatic injury is suspected. [ see Use in Specific Populations ( 8.7 ) ] 2.4 Drug Discontinuation If therapy needs to be discontinued, particularly in patients who have been receiving high doses (20 mg to 36 mg daily) for long periods (9 weeks or more) or who may be on concomitant treatment with narcotics, the dose should be decreased slowly (2 mg to 4 mg per day) to minimize the risk of withdrawal and rebound hypertension, tachycardia, and hypertonia [ see Drug Abuse and Dependence ( 9.3 )]. • Recommended starting dose: 2 mg; dose can be repeated at 6 to 8 hour intervals, up to a maximum of 3 doses in 24 hours ( Error! Hyperlink reference not valid. ) • Dosage can be increased by 2 mg to 4 mg per dose, with 1 to 4 days between increases; total daily dose should not exceed 36 mg ( Error! Hyperlink reference not valid. ) • Tizanidine pharmacokinetics differs between tablets and capsules, and when taken with or without food. These differences could result in a change in tolerability and control of symptoms ( Error! Hyperlink reference not valid. , 12.3 ) • To discontinue Tizanidine Tablets, USP, decrease dose slowly to minimize the risk of withdrawal and rebound hypertension, tachycardia, and hypertonia ( Error! Hyperlink reference not valid. )

WARNINGS AND PRECAUTIONS 5.1 Hypotension Tizanidine is an α 2 -adrenergic agonist that can produce hypotension. Syncope has been reported in the post marketing setting. The chance of significant hypotension may possibly be minimized by titration of the dose and by focusing attention on signs and symptoms of hypotension prior to dose advancement. In addition, patients moving from a supine to fixed upright position may be at increased risk for hypotension and orthostatic effects. Monitor for hypotension when Tizanidine Tablets, USP is used in patients receiving concurrent antihypertensive therapy. It is not recommended that Tizanidine Tablets, USP be used with other α 2 -adrenergic agonists. Clinically significant hypotension (decreases in both systolic and diastolic pressure) has been reported with concomitant administration of either fluvoxamine or ciprofloxacin and single doses of 4 mg of Tizanidine Tablets, USP. Therefore, concomitant use of Tizanidine Tablets, USP with fluvoxamine or with ciprofloxacin, potent inhibitors of CYP1A2, is contraindicated [ see Contraindications (4) andDrug Interactions ( Error! Hyperlink reference not valid. , Error! Hyperlink reference not valid. ) ]. 5.2 Risk of Liver Injury Tizanidine Tablets, USP may cause hepatocellular liver injury. Tizanidine Tablets, USP should be used with caution in patients with any hepatic impairment. Monitoring of aminotransferase levels is recommended for baseline and 1 month after maximum dose is achieved, or if hepatic injury is suspected. [ see Dosage and Administration ( Error! Hyperlink reference not valid. ) and Use in Specific Populations ( 8.7 ) ] 5.3 Sedation Tizanidine Tablets, USP can cause sedation, which may interfere with everyday activity. In the multiple dose studies, the prevalence of patients with sedation peaked following the first week of titration and then remained stable for the duration of the maintenance phase of the study. The CNS depressant effects of Tizanidine Tablets, USP with alcohol and other CNS depressants (e.g., benzodiazepines, opioids, tricyclic antidepressants) may be additive. Monitor patients who take Tizanidine Tablets, USP with another CNS depressant for symptoms of excess sedation. [ see Drug Interactions ( Error! Hyperlink reference not valid. , Error! Hyperlink reference not valid. ) ] 5.4 Hallucinosis/Psychotic-Like Symptoms Tizanidine Tablets, USP use has been associated with hallucinations. Formed, visual hallucinations or delusions have been reported in 5 of 170 patients (3%) in two North American controlled clinical studies. Most of the patients were aware that the events were unreal. One patient developed psychosis in association with the hallucinations. One patient among these 5 continued to have problems for at least 2 weeks following discontinuation of tizanidine. Consider discontinuing Tizanidine Tablets, USP in patients who develop hallucinations. 5.5 Interaction with CYP1A2 Inhibitors Because of potential drug interactions, Tizanidine Tablets, USP is contraindicated in patients taking potent CYP1A2 inhibitors, such as fluvoxamine or ciprofloxacin. Adverse reactions such as hypotension, bradycardia, or excessive drowsiness can occur when Tizanidine Tablets, USP is taken with other CYP1A2 inhibitors, such as zileuton, fluoroquinolones other than ciprofloxacin (which is contraindicated), antiarrythmics (amiodarone, mexiletine, propafenone), cimetidine, famotidine, oral contraceptives, acyclovir, and ticlopidine). Concomitant use should be avoided unless the necessity for Tizanidine Tablets, USP therapy is clinically evident. In such a case, use with caution. [ see Drug Interactions ( Error! Hyperlink reference not valid. ) and Clinical Pharmacology ( 12.3 ) ] 5.6 Hypersensitivity Reactions Tizanidine Tablets, USP can cause anaphylaxis. Signs and symptoms including respiratory compromise, urticaria, and angioedema of the throat and tongue have been reported. Patients should be informed of the signs and symptoms of severe allergic reactions and instructed to discontinue Tizanidine Tablets, USP and seek immediate medical care should these signs and symptoms occur. [ see Contraindications (4) ] 5.7 Increased Risk of Adverse Reactions in Patients with Renal Impairment Tizanidine Tablets, USP should be used with caution in patients with renal insufficiency (creatinine clearance < 25 mL/min), as clearance is reduced by more than 50%. In these patients, during titration, the individual doses should be reduced. If higher doses are required, individual doses rather than dosing frequency should be increased. These patients should be monitored closely for the onset or increase in severity of the common adverse events (dry mouth, somnolence, asthenia and dizziness) as indicators of potential overdose. [ see Dosage and Administration ( Error! Hyperlink reference not valid. ) and Use in Specific Populations ( 8.6 ) ] 5.8 Withdrawal Adverse Reactions Withdrawal adverse reactions include rebound hypertension, tachycardia, and hypertonia. To minimize the risk of these reactions, particularly in patients who have been receiving high doses (20 to 28 mg daily) for long periods of time (9 weeks or more) or who may be on concomitant treatment with narcotics, the dose should be decreased slowly (2 to 4 mg per day). [see Dosage and Administration ( Error! Hyperlink reference not valid. )] • Hypotension: monitor for signs and symptoms of hypotension, in particular in patients receiving concurrent antihypertensives; Tizanidine Tablets, USP should not be used with other α 2 -adrenergic agonists ( Error! Hyperlink reference not valid. , Error! Hyperlink reference not valid. ) • Risk of liver injury: monitor ALTs; discontinue Tizanidine Tablets, USP if liver injury occurs ( Error! Hyperlink reference not valid. ) • Sedation: Tizanidine Tablets, USP may interfere with everyday activities; sedative effects of Tizanidine Tablets, USP, alcohol, and other CNS depressants are additive ( Error! Hyperlink reference not valid. , Error! Hyperlink reference not valid. , Error! Hyperlink reference not valid. ) • Hallucinations: consider discontinuation of Tizanidine Tablets, USP ( Error! Hyperlink reference not valid. ) • Less potent inhibitors of CYP1A2: may cause hypotension, bradycardia, or excessive drowsiness, use caution if Tizanidine Tablets, USP is used with less potent inhibitors of CYP1A2, e.g., zileuton, other fluoroquinolones, antiarrythmics, cimetidine, famotidine, oral contraceptives, acyclovir, and ticlopidine ( Error! Hyperlink reference not valid. , Error! Hyperlink reference not valid. , 12.3 ) • Renal impairment (creatinine clearance < 25 mL/min): use Tizanidine Tablets, USP with caution, and monitor closely for dry mouth, somnolence, asthenia and dizziness as indicators of potential overdose ( Error! Hyperlink reference not valid. )

CONTRAINDICATIONS SECTION Concomitant use of tizanidine with fluvoxamine or with ciprofloxacin, potent inhibitors of CYP1A2, is contraindicated. Significant alterations of pharmacokinetic parameters of tizanidine including increased AUC, t1/2, Cmax, increased oral bioavailability and decreased plasma clearance have been observed with concomitant administration of either fluvoxamine or ciprofloxacin. This pharmacokinetic interaction can result in potentially serious adverse events (See WARNINGS and CLINICAL PHARMACOLOGY: Drug Interactions). Tizanidine tablets is contraindicated in patients with known hypersensitivity to Tizanidine tablets or its ingredients.

12. Clinical Pharmacology 12.1 Mechanism of Action Tizanidine is a central alpha-2-adrenergic receptor agonist and presumably reduces spasticity by increasing presynaptic inhibition of motor neurons. The effects of tizanidine are greatest on polysynaptic pathways. The overall effect of these actions is thought to reduce facilitation of spinal motor neurons. 12.3 Pharmacokinetics Absorption and Distribution Following oral administration, tizanidine is essentially completely absorbed. The absolute oral bioavailability of tizanidine is approximately 40% (CV = 24%), due to extensive first-pass hepatic metabolism. Tizanidine is extensively distributed throughout the body with a mean steady state volume of distribution of 2.4 L/kg (CV = 21%) following intravenous administration in healthy adult volunteers. Tizanidine is approximately 30% bound to plasma proteins. Differences between Tizanidine Capsules and Tizanidine Tablets Tizanidine capsules and tizanidine tablets are bioequivalent to each other under fasting conditions, but not under fed conditions. A single dose of either two 4 mg tablets or two 4 mg capsules was administered under fed and fasting conditions in an open label, four period, randomized crossover study in 96 human volunteers, of whom 81 were eligible for the statistical analysis. Following oral administration of either the tablet or capsule (in the fasted state), peak plasma concentrations of tizanidine occurred 1 hours after dosing with a half-life of approximately 2 hours. When two 4 mg tablets were administered with food, the mean maximal plasma concentration was increased by approximately 30%, and the median time to peak plasma concentration was increased by 25 minutes, to 1 hour and 25 minutes. In contrast, when two 4 mg capsules were administered with food, the mean maximal plasma concentration was decreased by 20%, the median time to peak plasma concentration was increased 2 to 3 hours. Consequently, the mean Cmax for the capsule when administered with food is approximately 66% the Cmax for the tablet when administered with food. Food also increased the extent of absorption for both the tablets and capsules. The increase with the tablet (~30%) was significantly greater than with the capsule (~10%). Consequently when each was administered with food, the amount absorbed from the capsule was about 80% of the amount absorbed from the tablet. Administration of the capsule contents sprinkled on applesauce was not bioequivalent to administration of an intact capsule under fasting conditions. Administration of the capsule contents on applesauce resulted in a 15% to 20% increase in Cmax and AUC of tizanidine and a 15 minute decrease in the median lag time and time to peak concentration compared to administration of an intact capsule while fasting. Figure 1: Mean Tizanidine Concentration vs. Time Profiles For Tizanidine Tablets and Capsules (2 × 4 mg) Under Fasted and Fed Conditions Metabolism and Excretion Tizanidine has linear pharmacokinetics over the doses studied in clinical development (1 to 20 mg). Tizanidine has a half-life of approximately 2.5 hours (CV=33%). Approximately 95% of an administered dose is metabolized. The primary cytochrome P450 isoenzyme involved in tizanidine metabolism is CYP1A2. Tizanidine metabolites are not known to be active; their half-lives range from 20 to 40 hours. Following single and multiple oral dosing of 14C-tizanidine, an average of 60% and 20% of total radioactivity was recovered in the urine and feces, respectively. Special Populations Age Effects No specific pharmacokinetic study was conducted to investigate age effects. Cross study comparison of pharmacokinetic data following single dose administration of 6 mg tizanidine hydrochloride showed that younger subjects cleared the drug four times faster than the elderly subjects. Tizanidine hydrochloride has not been evaluated in children. [see Use in Specific Populations (8.4, 8.5)] Hepatic Impairment The influence of hepatic impairment on the pharmacokinetics of tizanidine has not been evaluated. Because tizanidine is extensively metabolized in the liver, hepatic impairment would be expected to have significant effects on pharmacokinetics of tizanidine. Tizanidine hydrochloride is not recommended in this patient population [see Use in Specific Populations (8.7)] Renal Impairment Tizanidine clearance is reduced by more than 50% in elderly patients with renal insufficiency (creatinine clearance < 25 mL/min) compared to healthy elderly subjects; this would be expected to lead to a longer duration of clinical effect. Tizanidine hydrochloride should be used with caution in renally impaired patients [see Warnings and Precautions (5.7) and Use in Specific Populations (8.6)]. Gender Effects No specific pharmacokinetic study was conducted to investigate gender effects. Retrospective analysis of pharmacokinetic data, however, following single and multiple dose administration of 4 mg tizanidine hydrochloride showed that gender had no effect on the pharmacokinetics of tizanidine. Race Effects Pharmacokinetic differences due to race have not been studied. Drug Interactions CYP1A2 Inhibitors The interaction between tizanidine hydrochloride and either fluvoxamine or ciprofloxacin is most likely due to inhibition of CYP1A2 by fluvoxamine or ciprofloxacin. The effect of fluvoxamine on the pharmacokinetics of a single 4 mg dose of tizanidine hydrochloride was studied in 10 healthy subjects. The Cmax, AUC, and half-life of tizanidine increased by 12- fold, 33-fold, and 3-fold, respectively. The effect of ciprofloxacin on the pharmacokinetics of a single 4 mg dose of tizanidine hydrochloride was studied in 10 healthy subjects. The Cmax and AUC of tizanidine increased by 7-fold and 10-fold, respectively. [see Contraindications (4)] Although there have been no clinical studies evaluating the effects of other CYP1A2 inhibitors on tizanidine, other CYP1A2 inhibitors, such as zileuton, other fluoroquinolones, antiarrythmics (amiodarone, mexiletine, propafenone and verapamil), cimetidine, famotidine oral contraceptives, acyclovir and ticlopidine, may also lead to substantial increases in tizanidine blood concentrations [see Warnings and Precautions (5.5)]. In vitro studies of cytochrome P450 isoenzymes using human liver microsomes indicate that neither tizanidine nor the major metabolites are likely to affect the metabolism of other drugs metabolized by cytochrome P450 isoenzymes. Oral Contraceptives No specific pharmacokinetic study was conducted to investigate interaction between oral contraceptives and tizanidine hydrochloride. Retrospective analysis of population pharmacokinetic data following single and multiple dose administration of 4 mg tizanidine hydrochloride, however, showed that women concurrently taking oral contraceptives had 50% lower clearance of tizanidine compared to women not on oral contraceptives [see Warnings and Precautions (5.5)]. Acetaminophen Tizanidine delayed the Tmax of acetaminophen by 16 minutes. Acetaminophen did not affect the pharmacokinetics of tizanidine. Alcohol Alcohol increased the AUC of tizanidine by approximately 20%, while also increasing its Cmax by approximately 15%. This was associated with an increase in side effects of tizanidine. The CNS depressant effects of tizanidine and alcohol are additive. Fig 1