1. Name Of The Medicinal Product
'PRIMAXIN' IV 500 mg powder for solution for infusion
2. Qualitative And Quantitative Composition
Each vial contains imipenem monohydrate equivalent to 500 mg imipenem anhydrate and cilastatin sodium equivalent to 500 mg cilastatin.
Each vial contains sodium bicarbonate equivalent to approximately 1.6 mEq of sodium (approximately 37.6 mg).
For a full list of excipients, see section 6.1.
3. Pharmaceutical Form
Powder for solution for infusion.
White to light yellow powder.
4. Clinical Particulars
4.1 Therapeutic Indications
'PRIMAXIN' is indicated for the treatment of the following infections in adults and children 1 year of age and above (see sections 4.4 and 5.1):
• complicated intra-abdominal infections
• severe pneumonia including hospital and ventilator-associated pneumonia
• intra- and post-partum infections
• complicated urinary tract infections
• complicated skin and soft-tissue infections
'PRIMAXIN' may be used in the management of neutropenic patients with fever that is suspected to be due to a bacterial infection.
Treatment of patients with bacteraemia that occurs in association with, or is suspected to be associated with, any of the infections listed above.
Consideration should be given to official guidance on the appropriate use of antibacterial agents.
4.2 Posology And Method Of Administration
Posology
The dose recommendations for 'PRIMAXIN' represent the quantity of imipenem/cilastatin to be administered.
The daily dose of 'PRIMAXIN' should be based on the type and severity of infection, the pathogen(s) isolated, the patient's renal function and body weight (see also section 4.4 and 5.1).
Adults and adolescents
For patients with normal renal function (creatinine clearance of >70 ml/min/1.73 m2), the recommended dose regimens are:
500 mg/500 mg every 6 hours OR
1000 mg/1000 mg every 8 hours OR every 6 hours
It is recommended that infections suspected or proven to be due to less susceptible bacterial species (such as Pseudomonas aeruginosa) and very severe infections (e.g. in neutropenic patients with a fever) should be treated with 1000 mg/1000 mg administered every 6 hours.
A reduction in dose is necessary when:
- creatinine clearance is 2 (see Table 1) or
- body weight is < 70 kg. The proportionate dose for patients < 70 kg would be calculated using the following formula:
The maximum total daily dose should not exceed 4000 mg//4000 mg per day.
Renal impairment
To determine the reduced dose for adults with impaired renal function:
1. The total daily dose (i.e. 2000/2000, 3000/3000 or 4000/4000 mg) that would usually be applicable to patients with normal renal function should be selected.
2. From table 1 the appropriate reduced dose regimen is selected according to the patient's creatinine clearance. For infusion times see Method of administration.
Table 1: Reduced dose in adults with impaired renal function and body weight *
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* A further proportionate reduction in dose administered must be made for patients with a body weight <70 kg. The proportionate dose for patients <70 kg would be calculated by dividing the patient's actual body weight (in kg) by 70 kg multiplied by the respective dose recommended in Table 1.
** When the 500 mg/500 mg dose is used in patients with creatinine clearances of 6 to 20 ml/min/1.73 m2, there may be an increased risk of seizures.
Patients with a creatinine clearance of 2
These patients should not receive 'PRIMAXIN' unless haemodialysis is instituted within 48 hours.
Patients on haemodialysis
When treating patients with creatinine clearances of 2 who are undergoing dialysis use the dose recommendation for patients with creatinine clearances of 6 to 20 ml/min/1.73 m2 (see table 1).
Both imipenem and cilastatin are cleared from the circulation during haemodialysis. The patient should receive 'PRIMAXIN' after haemodialysis and at 12 hour intervals timed from the end of that haemodialysis session. Dialysis patients, especially those with background central nervous system (CNS) disease, should be carefully monitored; for patients on haemodialysis, 'PRIMAXIN' is recommended only when the benefit outweighs the potential risk of seizures (see section 4.4).
Currently there are inadequate data to recommend use of 'PRIMAXIN' for patients on peritoneal dialysis.
Hepatic impairment
No dose adjustment is recommended in patients with impaired hepatic function (see section 5.2).
Elderly population
No dose adjustment is required for the elderly patients with normal renal function (see section 5.2).
Paediatric population
For paediatric patients
It is recommended that infections suspected or proven to be due to less susceptible bacterial species (such as Pseudomonas aeruginosa) and very severe infections (e.g. in neutropenic patients with a fever) should be treated with 25/25 mg/kg administered every 6 hours.
Paediatric population <1 year of age
Clinical data are insufficient to recommend dosing for children less than 1 year of age
Paediatric population with renal impairment
Clinical data are insufficient to recommend dosing for paediatric patients with renal impairment (serum creatinine > 2 mg/dl). See section 4.4.
Method of administration
'PRIMAXIN' is to be reconstituted and further diluted (see section 6.2, 6.3 and 6.6) prior to administration. Each dose of
4.3 Contraindications
• Hypersensitivity to the active substances or to any of the excipients
• Hypersensitivity to any other carbapenem antibacterial agent
• Severe hypersensitivity (e.g. anaphylactic reaction, severe skin reaction) to any other type of beta-lactam antibacterial agent (e.g. penicillins or cephalosporins).
4.4 Special Warnings And Precautions For Use
General
The selection of imipenem/cilastatin to treat an individual patient should take into account the appropriateness of using a carbapenem antibacterial agent based on factors such as severity of the infection, the prevalence of resistance to other suitable antibacterial agents and the risk of selecting for carbapenem-resistant bacteria.
Hypersensitivity
Serious and occasionally fatal hypersensitivity (anaphylactic) reactions have been reported in patients receiving therapy with beta-lactams. These reactions are more likely to occur in individuals with a history of sensitivity to multiple allergens. Before initiating therapy with 'PRIMAXIN', careful inquiry should be made concerning previous hypersensitivity reactions to carbapenems, penicillins, cephalosporins, other beta-lactams and other allergens (see section 4.3). If an allergic reaction to 'PRIMAXIN' occurs, discontinue the therapy immediately. Serious anaphylactic reactions require immediate emergency treatment.
Hepatic
Hepatic function should be closely monitored during treatment with imipenem/cilastatin due to the risk of hepatic toxicity (such as increase in transaminases, hepatic failure and fulminant hepatitis).
Use in patients with liver disease: patients with pre-existing liver disorders should have liver function monitored during treatment with imipenem/cilastatin. There is no dose adjustment necessary (see section 4.2).
Haematology
A positive direct or indirect Coombs test may develop during treatment with imipenem/cilastatin.
Antibacterial spectrum
The antibacterial spectrum of imipenem/cilastatin should be taken into account especially in life-threatening conditions before embarking on any empiric treatment. Furthermore, due to the limited susceptibility of specific pathogens associated with e.g. bacterial skin and soft-tissue infections, to imipenem/cilastatin, caution should be exercised. The use of imipenem/cilastatin is not suitable for treatment of these types of infections unless the pathogen is already documented and known to be susceptible or there is a very high suspicion that the most likely pathogen(s) would be suitable for treatment. Concomitant use of an appropriate anti-MRSA agent may be indicated when MRSA infections are suspected or proven to be involved in the approved indications. Concomitant use of an aminoglycoside may be indicated when Pseudomonas aeruginosa infections are suspected or proven to be involved in the approved indications (see section 4.1).
Interaction with valproic acid
The concomitant use of imipenem/cilastatin and valproic acid/sodium valproate is not recommended (see section 4.5).
Clostridium difficile
Antibiotic-associated colitis and pseudomembranous colitis have been reported with imipenem/cilastatin and with nearly all other anti-bacterial agents and may range from mild to life-threatening in severity. It is important to consider this diagnosis in patients who develop diarrhoea during or after the use of imipenem/cilastatin (see section 4.8). Discontinuation of therapy with imipenem/cilastatin and the administration of specific treatment for Clostridium difficile should be considered. Medicinal products that inhibit peristalsis should not be given.
Meningitis
'PRIMAXIN' is not recommended for the therapy of meningitis.
Central nervous system
CNS adverse reactions such as myoclonic activity, confusional states, or seizures have been reported, especially when recommended doses based on renal function and body weight were exceeded. These experiences have been reported most commonly in patients with CNS disorders (e.g. brain lesions or history of seizures) and/or compromised renal function in whom accumulation of the administered entities could occur. Hence close adherence to recommended dose schedules is urged especially in these patients (see section 4.2). Anticonvulsant therapy should be continued in patients with a known seizure disorder.
Special awareness should be made to neurological symptoms or convulsions in children with known risk factors for seizures, or on concomitant treatment with medicinal products lowering the seizures threshold.
If focal tremors, myoclonus, or seizures occur, patients should be evaluated neurologically and placed on anticonvulsant therapy if not already instituted. If CNS symptoms continue, the dose of 'PRIMAXIN' should be decreased or discontinued.
Patients with creatinine clearances of 2 should not receive 'PRIMAXIN' unless haemodialysis is instituted within 48 hours. For patients on haemodialysis, 'PRIMAXIN' is recommended only when the benefit outweighs the potential risk of seizures (see section 4.2).
Paediatric use
Clinical data are insufficient to recommend the use of 'PRIMAXIN' in children under 1 year of age or paediatric patients with impaired renal function (serum creatinine >2 mg/dl). See also above under Central nervous system.
'PRIMAXIN' 500 mg/500 mg contains 37.6 mg of sodium (1.6 mEq) which should be taken into consideration by patients on a controlled sodium diet.
4.5 Interaction With Other Medicinal Products And Other Forms Of Interaction
Generalized seizures have been reported in patients who received ganciclovir and 'PRIMAXIN'. These medicinal products should not be used concomitantly unless the potential benefit outweighs the risks.
Decreases in valproic acid levels that may fall below the therapeutic range have been reported when valproic acid was co-administered with carbapenem agents. The lowered valproic acid levels can lead to inadequate seizure control; therefore, concomitant use of imipenem and valproic acid/sodium valproate is not recommended and alternative antibacterial or anti-convulsant therapies should be considered (see section 4.4).
Oral anti-coagulants
Simultaneous administration of antibiotics with warfarin may augment its anti-coagulant effects.
There have been many reports of increases in the anti-coagulant effects of orally administered anti-coagulant agents, including warfarin in patients who are concomitantly receiving antibacterial agents. The risk may vary with the underlying infection, age and general status of the patient so that the contribution of the antibiotic to the increase in INR (international normalised ratio) is difficult to assess. It is recommended that the INR should be monitored frequently during and shortly after co-administration of antibiotics with an oral anti-coagulant agent.
Concomitant administration of 'PRIMAXIN' and probenecid resulted in minimal increases in the plasma levels and plasma half-life of imipenem. The urinary recovery of active (non-metabolised) imipenem decreased to approximately 60% of the dose when 'PRIMAXIN' was administered with probenecid. Concomitant administration of 'PRIMAXIN' and probenecid doubled the plasma level and half-life of cilastatin, but had no effect on urine recovery of cilastatin.
4.6 Pregnancy And Lactation
Pregnancy
There are no adequate and well-controlled studies for the use of imipenem/cilastatin in pregnant women.
Studies in pregnant monkeys have shown reproductive toxicity (see section 5.3). The potential risk for humans is unknown.
'PRIMAXIN' should be used during pregnancy only if the potential benefit justifies the potential risk to the foetus.
Breast-feeding
Imipenem and cilastatin are excreted into the mother's milk in small quantities. Little absorption of either compound occurs following oral administration. Therefore it is unlikely that the suckling infant will be exposed to significant quantities. If the use of 'PRIMAXIN' is deemed necessary, the benefit of breast feeding for the child should be weighed against the possible risk for the child.
Fertility
There are no data available regarding potential effects of imipenem/cilastatin treatment on male or female fertility.
4.7 Effects On Ability To Drive And Use Machines
No studies on the effects on the ability to drive and use machines have been performed. However, there are some side effects (such as hallucination, dizziness, somnolence, and vertigo) associated with this product that may affect some patients' ability to drive or operate machinery (see section 4.8).
4.8 Undesirable Effects
In clinical trials including 1,723 patients treated with imipenem/cilastatin intravenous the most frequently reported systemic adverse reactions that were reported at least possibly related to therapy were nausea (2.0%), diarrhoea (1.8%), vomiting (1.5%), rash (0.9%), fever (0.5%), hypotension (0.4%), seizures (0.4%) (see section 4.4), dizziness (0.3%), pruritus (0.3%), urticaria (0.2%), somnolence (0.2%). Similarly, the most frequently reported local adverse reactions were phlebitis/thrombophlebitis (3.1%), pain at the injection site (0.7%), erythema at the injection site (0.4%) and vein induration (0.2%). Increases in serum transaminases and in alkaline phosphatase are also commonly reported.
The following adverse reactions have been reported in clinical studies or during post-marketing experience.
All adverse reactions are listed under system organ class and frequency: Very common (
Within each frequency grouping, undesirable effects are presented in order of decreasing seriousness.
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Paediatric (3 months of age)
In studies of 178 paediatric patients
4.9 Overdose
Symptoms of overdose that can occur are consistent with the adverse reaction profile; these may include seizures, confusion, tremors, nausea, vomiting, hypotension, bradycardia. No specific information is available on treatment of overdose with 'PRIMAXIN'. Imipenem-cilastatin sodium is haemodialyzable. However, usefulness of this procedure in the overdose setting is unknown.
5. Pharmacological Properties
5.1 Pharmacodynamic Properties
Pharmacotherapeutic group: Antibacterials for systemic use, carbapenems, ATC code: J01D H51
Mode of action
'PRIMAXIN' consists of two components: imipenem and cilastatin sodium in a 1:1 ratio by weight.
Imipenem, also referred to as N-formimidoyl-thienamycin, is a semi-synthetic derivative of thienamycin, the parent compound produced by the filamentous bacterium Streptomyces cattleya.
Imipenem exerts its bactericidal activity by inhibiting bacterial cell wall synthesis in Gram-positive and Gram-negative bacteria through binding to penicillin-binding proteins (PBPs).
Cilastatin sodium is a competitive, reversible and specific inhibitor of dehydropeptidase-I, the renal enzyme which metabolizes and inactivates imipenem. It is devoid of intrinsic antibacterial activity and does not affect the antibacterial activity of imipenem.
Pharmacokinetic/Pharmacodynamic (PK/PD) relationship
Similar to other beta-lactam antibacterial agents, the time that imipenem concentrations exceed the MIC (T>MIC) has been shown to best correlate with efficacy.
Mechanism of resistance
Resistance to imipenem may be due to the following:
• Decreased permeability of the outer membrane of Gram-negative bacteria (due to diminished production of porins)
• Imipenem may be actively removed from the cell with an efflux pump.
• Reduced affinity of PBPs to imipenem
• Imipenem is stable to hydrolysis by most beta-lactamases, including penicillinases and cephalosporinases produced by gram-positive and gram-negative bacteria, with the exception of relatively rare carbapenem hydrolysing beta-lactamases. Species resistant to other carbapenems do generally express co-resistance to imipenem. There is no target-based cross-resistance between imipenem and agents of the quinolone, aminoglycoside, macrolide and tetracycline classes.
Breakpoints
EUCAST MIC breakpoints for imipenem to separate susceptible (S) pathogens from resistant (R) pathogens are as follows (v 1,1 2010-04-27):
• Enterobacteriaceae 1: S
• Pseudomonas spp. 2: S
• Acinetobacter spp.: S
• Staphylococcus spp. 3: Inferred from cefoxitin susceptibility
• Enterococcus spp.: S
• Streptococcus A, B, C, G: The beta-lactam susceptibility of beta-haemolytic streptococcus groups A, B, C and G is inferred from the penicillin susceptibility.
• Streptococcus pneumoniae 4: S
• Other streptococci 4: S
• Haemophilus influenzae 4: S
• Moraxalla catarrhalis 4: S
• Neisseria gonorrhoeae: There is insufficient evidence that Neisseria gonorrhoeae is a good target for therapy with imipenem.
• Gram-positive anaerobes: S
• Gram-negative anaerobes: S
• Non-species related breakpoints 5: S
1Proteus and Morganella species are considered poor targets for imipenem.
2 The breakpoints for Pseudomonas relate to high dose frequent therapy (1g every 6 hours).
3 Susceptibility of staphylococci to carbapenems is inferred from the cefoxitin susceptibility.
4 Strains with MIC values above the susceptible breakpoint are very rare or not yet reported. The identification and antimicrobial susceptibility tests on any such isolate must be repeated and if the result is confirmed the isolate must be sent to a reference laboratory. Until there is evidence regarding clinical response for confirmed isolates with MIC above the current resistant breakpoint they should be reported resistant.
5 Non-species related breakpoint have been determined mainly on the basis of PK/PD data and are independent of MIC distributions of specific species. They are for use only for species not mentioned in the overview of species-related breakpoints or footnotes.
Susceptibility
The prevalence of acquired resistance may vary geographically and with time for selected species and local information on resistance is desirable, particularly when treating severe infections. As necessary, expert advice should be sought when the local prevalence of resistance is such that the utility of the agent in at least some types of infections is questionable.
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* All methicillin-resistant staphylococci are resistant to imipenem/cilastatin.
** EUCAST non-species related breakpoint is used.
5.2 Pharmacokinetic Properties
Imipenem
Plasma concentrations
In normal volunteers, intravenous infusion of 'PRIMAXIN' over 20 minutes resulted in peak plasma levels of imipenem ranging from 12 to 20 μg/ml for the 250 mg/250 mg dose, from 21 to 58 μg/ml for the 500 mg/500 mg dose, and from 41 to 83 μg/ml for the 1000 mg/1000 mg dose. The mean peak plasma levels of imipenem following the 250 mg/250 mg, 500 mg/500 mg, and 1000 mg /1000 mg doses were 17, 39, and 66 μg/ml, respectively. At these doses, plasma levels of imipenem decline to below 1 μg/ml or less in four to six hours.
Distribution
The binding of imipenem to human serum proteins is approximately 20%.
Biotransformation and elimination
When administered alone, imipenem is metabolised in the kidneys by dehydropeptidase-I. Individual urinary recoveries ranged from 5 to 40%, with an average recovery of 15-20% in several studies.
Cilastatin is a specific inhibitor of dehydropeptidase-I enzyme and effectively inhibits metabolism of imipenem so that concomitant administration of imipenem and cilastatin allows therapeutic antibacterial levels of imipenem to be attained in both urine and plasma.
The plasma half-life of imipenem was one hour. Approximately 70% of the administered antibiotic was recovered intact in the urine within ten hours, and no further urinary excretion of imipenem was detectable. Urine concentrations of imipenem exceeded 10 μg/ml for up to eight hours after a 500 mg/500 mg dose of 'PRIMAXIN'. The remainder of the administered dose was recovered in the urine as antibacterially inactive metabolites, and faecal elimination of imipenem was essentially nil.
No accumulation of imipenem in plasma or urine has been observed with regimens of 'PRIMAXIN', administered as frequently as every six hours, in patients with normal renal function.
Cilastatin
Plasma concentrations
Peak plasma levels of cilastatin, following a 20 minute intravenous infusion of 'PRIMAXIN', ranged from 21 to 26 μg/ml for the 250 mg/250 mg dose, from 21 to 55 μg/ml for the 500 mg/500 mg dose and from 56 to 88 μg/ml for the 1000 mg/1000 mg dose. The mean peak plasma levels of cilastatin following the 250 mg/250 mg, 500 mg/500 mg, and 1000 mg/1000 mg doses were 22, 42, and 72 µg/ml respectively.
Distribution
The binding of cilastatin to human serum proteins is approximately 40%.
Biotransformation and elimination
The plasma half-life of cilastatin is approximately one hour. Approximately 70-80% of the dose of cilastatin was recovered unchanged in the urine as cilastatin within 10 hours of administration of 'PRIMAXIN'. No further cilastatin appeared in the urine thereafter. Approximately 10% was found as the N-acetyl metabolite, which has inhibitory activity against dehydropeptidase comparable to that of cilastatin. Activity of dehydropeptidase-I in the kidney returned to normal levels shortly after the elimination of cilastatin from the blood stream.
Renal insufficiency
Following a single 250 mg/250 mg intravenous dose of 'PRIMAXIN', the area under the curve (AUCs) for imipenem increased 1.1-fold, 1.9-fold, and 2.7-fold in subjects with mild (Creatinine Clearance (CrCL) 50-80 ml/min/1.73 m2), moderate (CrCL 30-<50 ml/min/1.73 m2), and severe (CrCL <30 ml/min/1.73 m2) renal impairment, respectively, compared to subjects with normal renal function (CrCL >80 ml/min/1.73 m2), and AUCs for cilastatin increased 1.6-fold, 2.0-fold, and 6.2-fold in subjects with mild, moderate, and severe renal impairment, respectively, compared to subjects with normal renal function. Following a single 250 mg/250 mg intravenous dose of 'PRIMAXIN' given 24 hours after haemodialysis, AUCs for imipenem and cilastatin were 3.7-fold and 16.4-fold higher, respectively, as compared to subjects with normal renal function. Urinary recovery, renal clearance and plasma clearance of imipenem and cilastatin decrease with decreasing renal function following intravenous administration of
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