INTERACTIONS Formal PK drug-drug interaction studies have not been performed with PRIALT. As ziconotide is a peptide, it is expected to be completely degraded by endopeptidases and exopeptidases (Phase I hydrolytic enzymes) widely located throughout the body, and not by other Phase I biotransformation processes (including the cytochrome P450 system) or by Phase II conjugation reactions. Thus, intrathecal administration, low plasma ziconotide concentrations, and metabolism by ubiquitous peptidases make metabolic interactions of other drugs with ziconotide unlikely. Further, as ziconotide is not highly bound in plasma (approximately 50%) and has low plasma exposure following intrathecal administration, clinically relevant plasma protein displacement reactions involving ziconotide and co-administered medications are unlikely.
Over
90% of patients treated with intrathecal PRIALT used systemic opiates and in the slow titration study, 98% of patients received opioids. The combination of PRIALT with intrathecal opiates has not been studied in placebo-controlled clinical trials and is not recommended. Combination of PRIALT with intrathecal opiates is not recommended. ( 7 ) Patients taking concomitant antiepileptics, neuroleptics, sedatives, or diuretics may be at higher risk of depressed levels of consciousness. ( 5.3 ) The use of PRIALT may be associated with an increased incidence of CNS adverse reactions such as dizziness and confusion. ( 7.1 )
7.1 Interaction with CNS Depressants Almost all patients in the PRIALT clinical trials received concomitant non-intrathecal medication. Most patients received several concomitant drugs, including antidepressants (66%), anxiolytics (52%), antiepileptics (47%), neuroleptics (46%), and sedatives (34%). The use of drugs with CNS-depressant activities may be associated with an increased incidence of CNS adverse reactions such as dizziness and confusion [ see Warnings and Precautions ( 5 ) ].
PRIALT is contraindicated in patients with a known hypersensitivity to ziconotide or any of its formulation components. PRIALT is contraindicated in patients with any other concomitant treatment or medical condition that would render intrathecal administration hazardous. Contraindications to the use of intrathecal analgesia include the presence of infection at the microinfusion injection site, uncontrolled bleeding diathesis, and spinal canal obstruction that impairs circulation of CSF. PRIALT is contraindicated in patients with a pre-existing history of psychosis. Patients with a known hypersensitivity to ziconotide or any of its formulation components and in patients with any other concomitant treatment or medical condition that would render intrathecal administration hazardous. ( 4 ) Patients with a pre-existing history of psychosis with ziconotide. ( 4 ) Contraindications to the use of intrathecal analgesia include conditions such as the presence of infection at the microinfusion injection site, uncontrolled bleeding diathesis, and spinal canal obstruction that impairs circulation of cerebrospinal fluid (CSF). ( 4 )
AND PRECAUTIONS Cognitive and neuropsychiatric adverse reactions – Cognitive impairment and severe neuropsychiatric symptoms may occur with PRIALT use. ( 5.1 ) Meningitis and other infections – Patients, caregivers, and healthcare providers must be aware of the signs and symptoms of meningitis, including but not limited to fever, headache, stiff neck, altered mental status (e.g., lethargy, confusion, disorientation), nausea or vomiting, and occasionally seizures. ( 5.2 ) Reduced level of consciousness – Patients may become unresponsive or stuporous while receiving PRIALT. ( 5.3 ) Elevation of serum creatine kinase – Patients taking PRIALT may experience elevations in creatine kinase. Monitor serum CK in patients undergoing treatment with PRIALT periodically. ( 5.4 ) Withdrawal from opiates : Patients must not be abruptly withdrawn from opiates and must be gradually tapered over a few weeks and replaced with a pharmacologically equivalent dose of oral opiates. ( 5.5 )
5.1 Cognitive and Neuropsychiatric Adverse Reactions Severe psychiatric symptoms and neurological impairment may occur during treatment with PRIALT. PRIALT is contraindicated in patients with a pre-existing history of psychosis. Monitor all patients frequently for evidence of cognitive impairment, hallucinations, or changes in mood or consciousness. PRIALT therapy can be interrupted or discontinued abruptly without evidence of withdrawal effects in the event of serious neurological or psychiatric signs or symptoms. Events of acute psychiatric disturbances such as hallucinations (12%), paranoid reactions (3%), hostility (2%), delirium (2%), psychosis (1%), and manic reactions (0.4%) have been reported in patients treated with PRIALT. Patients with pretreatment psychiatric disorders may be at an increased risk. PRIALT may cause or worsen depression with the risk of suicide in susceptible patients. In placebo-controlled trials, there was a higher incidence of suicide, suicide attempts, and suicide ideations in PRIALT-treated patients than in the placebo group (0.27/patient year for PRIALT patients and 0.10/patient year for placebo patients). Management of psychiatric complications may need to include discontinuation of PRIALT, treatment with psychotherapeutic agents and/or short-term hospitalization. Before drug is reinitiated, careful evaluation must be performed on an individual basis. Use of PRIALT has been associated with cognitive impairment and decreased alertness/unresponsiveness. The following cognitive adverse reaction rates were reported: confusion (33%), memory impairment (22%), speech disorder (14%), aphasia (12%), thinking abnormal (8%), and amnesia (1%). Cognitive impairment may appear gradually after several weeks of treatment. Reduce the dose of PRIALT or discontinue the use of PRIALT if signs or symptoms of cognitive impairment develop, but other contributing causes must also be considered. The cognitive effects of PRIALT are generally reversible within 2 weeks after drug discontinuation. The median time to reversal of the individual cognitive effects ranged from 3 to 15 days. The elderly (≥ 65 years of age) are at higher risk for confusion. [ see Use in Specific Populations ( 8.5 ) ] There may be additive effects on cognitive impairment and decreased alertness when PRIALT is used in conjunction with other CNS-depressant drugs that may necessitate dosage adjustments.
5.2 Meningitis and Other Infections Meningitis can occur due to inadvertent contamination of the microinfusion device and other means such as CSF seeding due to hematogenous or direct spread from an infected pump pocket or catheter tract. While meningitis is rare with an internal microinfusion device and surgically-implanted catheter, the incidence increases substantially with external devices. In PRIALT clinical trials, meningitis occurred in 3% (40) of patients in the PRIALT group using either internal or external microinfusion devices and 1% (1 case) of patients in the placebo group. The risk of meningitis was particularly high in patients with external microinfusion devices and catheters, occurring in 38 out of 41 patients (93%), 37 of whom received PRIALT and one who received placebo. Patients, caregivers, and healthcare providers must be particularly vigilant for the signs and symptoms of meningitis, including but not limited to fever, headache, stiff neck, altered mental status (e.g., lethargy, confusion, disorientation), nausea or vomiting, and occasionally seizures. Serious infection or meningitis can occur within 24 hours of a breach in sterility such as a disconnected catheter, the most common cause of meningitis with external microinfusion devices. The patient and health care provider must be familiar with the handling of the external microinfusion device and care of the catheter skin exit site. Strict aseptic procedures must be used during the preparation of the PRIALT solution and refilling of the microinfusion device to decrease the risk of introducing contaminants or other environmental pathogens into the reservoir. In suspected cases (especially in immuno-compromised patients) or in confirmed cases of meningitis, CSF cultures must be obtained and appropriate antibiotic therapy must be promptly instituted. Treatment of meningitis usually requires removal of the microinfusion system, catheter, and any other foreign body materials within the intrathecal space and, therefore, discontinuation of PRIALT therapy.
5.3 Reduced Level of Consciousness Patients have become unresponsive or stuporous while receiving PRIALT. The incidence of unresponsiveness or stupor in clinical trials was 2% in PRIALT-treated patients. During these episodes, patients sometimes appear to be conscious and breathing is not depressed. If reduced levels of consciousness occur, discontinue PRIALT until the event resolves, and other etiologies (e.g., meningitis) must be considered. There is no known pharmacologic antagonist for this effect. Patients taking concomitant antiepileptics, neuroleptics, sedatives, or diuretics may be at higher risk of depressed levels of consciousness. If altered consciousness occurs, discontinue other CNS-depressant drugs as clinically appropriate.
5.4 Elevation of Serum Creatine Kinase In clinical studies, 40% of PRIALT-treated patients had serum creatine kinase (CK) levels above the upper limit of normal (ULN), and 11% had CK levels that were greater than three times the ULN. In cases where CK was fractionated, only the muscle isoenzyme (MM) was elevated. The time to occurrence was sporadic, but the greatest incidence of CK elevation was during the first two months of treatment. One case of symptomatic myopathy with EMG findings, and two cases of acute renal failure associated with rhabdomyolysis and extreme CK elevations (17,000–27,000 IU/L) have been reported in PRIALT-treated patients. Therefore, monitor serum CK in patients undergoing treatment with PRIALT periodically (e.g., every other week for the first month and monthly as appropriate thereafter). Evaluate patients clinically and obtain CK measurements in the setting of new neuromuscular symptoms (e.g., myalgias, myasthenia, muscle cramps, asthenia) or a reduction in physical activity. If these symptoms continue and CK levels remain elevated or continue to rise, reduce the dose or discontinue the use of PRIALT.
5.5 Withdrawal From Opiates PRIALT is not an opiate and cannot prevent or relieve the symptoms associated with the withdrawal of opiates. To avoid withdrawal syndrome when opiate withdrawal is necessary, do not abruptly reduce or withdraw opioid medications. For patients being withdrawn from intrathecal opiates or intrathecal opiate infusion, gradually taper over a few weeks and replace with a pharmacologically equivalent dose of oral opiates.
5.6 Driving and Operating Machinery Use of PRIALT has been associated with cognitive impairment and decreased alertness/unresponsiveness. Therefore, caution patients against engaging in hazardous activities that require complete mental alertness or motor coordination such as operating machinery or driving a motor vehicle.