Drug safety 25 a/w

3 2 n d E D I T I O N
Carbapenems: Interaction with sodium valproate
Doripenem monohydrate (marketed as Doribax), 4.4 Special warnings and precautions for use
a synthetic antibiotic, is a new chemical entity The concomitant use of doripenem and valproic that belongs to the carbapenem class of beta-lac- acid/sodium valproate is not recommended (see section tams. Doripenem is administered via intravenous route and is active against a range of Gram positive and Gram negative bacteria, as shown in vitro and in 4.5 Interaction with other medicinal products
animal models. Doripenem exhibits time dependent and other forms of interaction
It has been shown that co-administration of doripenem
bactericidal activity and moderate and short post- and valproic acid significantly reduces serum valproic antibiotic effect in vitro and in animal models.
acid levels below the therapeutic range. The lowered val- Doribax® is approved in the treatment of the fol- proic acid levels can lead to inadequate seizure control. In lowing infections caused by strains of bacteria sensi- an interaction study, the serum concentrations of valproic acid were markedly reduced (AUC was reduced by 63%)following co-administration of doripenem and valproic • Complicated urinary tract infections (UTI),
acid. The interaction had a fast onset. Since patients were administered only four doses of doripenem, further pyelonephritis and cases with concurrent bac- decrease of valproic acid levels with longer concomitant administration cannot be excluded. • Complicated intra-abdominal infections,
Decreases in valproic acid levels have also been • Nosocomial pneumonia, including ventilator-
reported when co-administered with other carbapenem • associated pneumonia (VAP).
agents, achieving a 60 -100 % decrease in valproic acidlevels in about two days. Therefore alternative antibacter- During an EU-based assessment of new pharmacoki- ial or anticonvulsant therapies should be considered.
netic data from an interaction study submitted by the The Package Leaflet (PL) will be updated accordingly.
Marketing Authorisation Holder, a highly significant interaction between doripenem and valproate was Advice to Healthcare Professionals:
identified. During concomitant administration, val- • Concomitant use of doripenem and valproic
proate levels decline rapidly and significantly. acid/sodium valproate should be avoided due to Other carbapenems licensed for use in Ireland are the large magnitude of the interaction and its not ertapenem, meropenem and imipenem. The interac- fully characterised time course. The lowered val- tion between valproate and carbapenems is estab- proic acid levels can lead to inadequate seizure lished and several case reports and at least one retrospective study1 describe a clinically relevant • It is considered that this interaction is a class effect
interaction (electroclinical deterioration). The mech- for carbapenems and a class review is ongoing.
anism of the interaction has not been fully eluci- The product information for Doribax® will be 1. Ann Pharmacother. 2007 Jul;41(7):1130-6.
updated to include the following warnings in sections 2. Drug Metab Rev. 2007;39(4):647-57.
Drug Safety – July 2009 – Issue Number 32 Correspondence/Comments should be sent to the Pharmacovigilance Section, Irish Medicines Board, Kevin O’Malley House, Earlsfort Centre, Earlsfort Terrace, Dublin 2.
associated with an increased risk of atypical stress Bisphosphonates and risk of stress
fractures (Alendronate/clodronate/
• The risk of atypical stress fractures with all bis-
etidronate/ibandronate/pamidronate/rise
phosphonates will be kept under close review by dronate/zoledronate)
the Irish Medicines Board and the European Med- icines Agency with consideration of further epi- Individual bisphosphonates are authorised for dif- demiological research and further information ferent indications, and are used in the treatment of will be issued to healthcare professionals when Pagets disease, prophylaxis and treatment of osteo- porosis, and as part of some cancer regimens.
Recent evidence from published literature suggests that long-term use of alendronic acid may be asso- 1 Kwek EB, et al. Injury 2008; 39: 224–31.
ciated with an increased risk of atypical stress frac- 2 Lenart BA, et al. N Engl J Med 2008; 358: 12.
tures.1–3 An EU review of bisphosphonates and 3 Neviaser AS, et al. J Orthop Trauma 2008; 22: 346–50.
atypical stress fractures analysed preclinical data, clinical-trial data, post marketing spontaneous reports of adverse drug reactions, published litera- Mycophenolate mofetil: pure red cell
ture and information from other drug regulatory The conclusions of the review can be subdivided into those relating specifically to alendronic acid and immunosuppressant indicated in combination those applicable to all other bisphosphonates as fol- with ciclosporin and corticosteroids for prophylaxis of acute transplant rejection in adults receiving allo- geneic renal, cardiac or hepatic transplants, and in Alendronate
children and adolescents (age 2–18 years) receiving Atypical stress fractures (insufficiency fractures) of the proximal femoral shaft have been reported in As of April 2009, 41 cases of pure red cell aplasia patients on long-term treatment with alendronate.
had been reported worldwide in association with In general, time to onset ranged from 18 months mycophenolate mofetil. Pure red cell aplasia is a type of anaemia in which there is a selective reduc- Fractures occurred after minimal or no trauma.
Some patients experienced thigh pain weeks to tion of red blood cell precursors on bone-marrow months before presenting with a completed examination. Some patients were also receiving femoral fracture. Fractures were frequently bilat- other medicines that could have contributed to the eral; therefore the contralateral femur should be development of pure red cell aplasia (e.g., alem- examined in patients treated with alendronate tuzumab, tacrolimus, azathioprine, and co-trimox- who have a femoral shaft fracture. Poor healing of azole). In four cases dose reduction, and in 12 cases discontinuation, of mycophenolate mofetil led to • Patients who develop atypical stress fractures
resolution of the condition. The mechanism by should discontinue alendronate and receive no which mycophenolate mofetil may cause pure red further bisphosphonate treatment unless the ben- efits of continued treatment are thought to clearly outweigh the risks to the individual.
Advice for healthcare professionals
• Product information for alendronate will be
updated to include a warning about atypical stress • Dose reduction or discontinuation of mycophe-
nolate mofetil should be considered in patients who develop pure red cell aplasia. Changes to All other bisphosphonates
treatment should be done only under specialist • Limited data are available for the other bisphos-
supervision to minimise the risk of graft rejec- phonates in support of a causal association with atypical stress fractures. This might reflect their • Further information is available in a Dear
lower usage and the limited long-term data that Healthcare Professional Communication distrib- uted by the Marketing Authorisation Holder in • The possibility that other bisphosphonates may be
June 2009 and published on the IMB website.
trol. Doses higher than 10 µg twice daily are not Exenatide (Byetta) – Risk of Severe
Pancreatitis and Warnings regarding use
There have been reports of necrotising and haem- in Renal Impairment.
orrhagic pancreatitis with exenatide, some of xenatide (Byetta), the first-in-class incretin If pancreatitis is suspected, treatment with exe- mimetic, is a glucagon-like-peptide-1 analogue natide should be suspended immediately; if pan- that stimulates insulin release from pancreatic β cells creatitis is diagnosed, exenatide should be in a glucose dependent manner. Exenatide is indi- cated for treatment of type 2 diabetes mellitus in com- Diagnosed pancreatitis with an unexpectedly prolonged course, haemodynamic instability, sulphonylureas in patients who have not achieved fever, failure of medical therapy, or presence of adequate glycaemic control on maximally tolerated fluid collections on CT suggest possible necrosis.
doses of these oral therapies. Exenatide should not be Exenatide is not recommended for use in patients used in patients with type 1 diabetes or for the treat- with end-stage renal disease or severe renal ment of diabetic ketoacidosis. It should not be used in impairment (creatinine clearance <30 mL/min).
patients with type 2 diabetes who require insulin As with all medicines, the safety of exenatide remains Exenatide was first marketed in the EU in Novem- under close review. Please continue to report all sus- ber 2006 and since then the IMB in conjunction with pected adverse reactions with exenatide to the IMB the European Medicines Agency (EMEA) has moni- either using a FREEPOST yellow adverse reaction tored its safety. Acute pancreatitis is a known adverse report card or via our website www.imb.ie.
effect of exenatide, but continued reporting of seri- ous and fatal cases has led to re-evaluation of this issue. To date, the IMB has received two confirmed reports of pancreatitis associated with the use of exe- Amphotericin – Recommendations for
natide. 396 case reports of pancreatitis have been Safe Prescription, Dispensing and
received worldwide in association with exenatide up Administration
to September 2008, mostly from the USA. There have been approximately 800 000 patient-years of expo- sure worldwide since licensing. 80% of the reports of Amphotericin is an antifungal agent licensed in Ireland for the treatment of systemic mycotic pancreatits were considered to be possibly related to infections including aspergillosis and cryptococco- exenatide, and in several cases there was evidence of sis. There are three different formulations of positive rechallenge. Nine reports of necrotising or amphotericin currently available on the Irish Mar- haemorrhagic pancreatitis have been received ket: non-lipid amphotericin deoxycholate complex worldwide, two of which had a fatal outcome. After (Fungizone®), liposomal amphotericin (AmBi- a Europe-wide review, the product information for some®) and lipid complex amphotericin (Abel- exenatide is being updated to include further infor- These amphotericin products are not interchange- Case reports of renal impairment have also been able and there are different licensed doses for each received in association with exenatide. This medi- cine is not recommended for use in patients with The IMB is aware of international reports of med- end-stage renal disease or severe renal impairment ication errors resulting from confusion between (creatinine clearance <30 mL/min). Clinical experi- amphotericin products which have resulted in a fatal ence in patients with moderate renal impairment is Confusion between the different formulations of Advice for healthcare professionals:
• Overdosing resulting in potentially fatal cardiac
Treatment with exenatide should be initiated at 5 µg twice daily for at least one month to improve • Under-dosing resulting in sub-therapeutic doses.
tolerability. The dose can then be increased to 10µg twice daily to further improve glycaemic con- Healthcare Professionals involved in prescription, dis- pensing and administration of amphotericin prod- A recent EU review of the evidence for such addi- tive hypotensive effects following co-administration • Amphotericin products are not interchangeable.
inhibitors included data available from clinical • When prescribing and dispensing amphotericin
interactions studies1-6 and spontaneous reports from products, it is recommended that both the com- plete generic name (International Non-Propri- etary Name/INN) and the proprietary name are The conclusion of this assessment was that the used, i.e. non-lipid amphotericin Fungizone®; interaction studies provided evidence of clinically liposomal amphotericin AmBisome®; or lipid relevant additive hypotensive effects if non-selective alpha-blockers and PDE-5-inhibitors were taken • It is essential to verify the dose of the product prior
concomitantly. In contrast, no such evidence was to prescribing, dispensing or administering espe- available for the so-called uro-selective alpha-block- cially if unfamiliar with the product.
ers. A limited number of spontaneous adverse reac- • Under no circumstances should a total daily dose
tion reports provided information on the possible of non-lipid amphotericin Fungizone® exceed The following warning will be added to the prod- uct information of the non-selective alpha-blockers.
Additional hypotensive effects following
"Concomitant use of phosphodiesterase-5-inhibitors co-administration of non-selective
(e.g. sildenafil, tadalafil, vardenafil) and /…/ may lead to alpha-blockers and phosphodiesterase-5-
symptomatic hypotension in some patients. In order to inhibitors
minimise the risk for developing postural hypotension the (Doxazosin/terazoin/prazosin/tamsulosin/alfuzosin/ patient should be stable on the alpha-blocker therapy before initiating use of phosphodiesterase-5-inhibitors." About 50% of men in their fifties have benign prostatic hyperplasia, and also about 50% suffer from erectile dysfunction. It is therefore 1) Auerbach S et al. Coadministered vardenafil (for erectile dys- function) and tamsulosin do not induce hypotension in patients plausible that a significant proportion of the male with benign prostatic hypertrophy. Am J Hyperten 2004;17:OR- population suffer from both conditions. Oral administration of phosphodiesterase-5-inhibitors 2) Giulano F et al. Hemodynamic interaction study between the (PDE-5-I) and alpha1-adrenoceptor (alpha) block- alpha1-blocker alfuzosin and the phosphodiesterase-5 inhibitor tadalafil in middle-aged healthy male subjects. Urology ers is the recommended therapy for erectile dysfunction and benign prostatic hyperplasia, 3) Guillaume M et al. Hemodynamic interaction between a daily respectively. Since both classes of drugs are dosed phosphodiesterase 5 inhibitor, tadalafil, and the alpha- vasodilators, their co-administration may result in adrenergic blockers, doxazosin and tamsulosin, in middle- additive hypotensive effects leading to (sympto- aged healthy male subjects. J Clin Pharmacol 2007; 4) Kaplan SA et al. Combination of alfuzosin and sildenafil is supe- rior to monotherapy in treating lower urinary tract symptoms The non-selective alpha blockers, doxa-, tera- and and erectile dysfunction. Eur Urol 2007;51:1717-23.
prazosin, which are also used for treatment of hyper- 5) Kloner RA. Pharmacology and drug interaction effects of the tension, carry a higher potential for this additive phosphodiesterase 5 inhibitors: Focus on alpha-blocker interac- tions. Am J Cardiol 2005; 96[suppl]:42M-46M. 6) Kloner RA. Interaction between the phosphodiesterase 5 inhibitors than uro-selective alpha blockers, tamsu- inhibitor tadalafil and 2 alpha-blockers, doxazosin and tamsu- losin in healthy normotensive men. J Urol 2004;172:1935-40. Drug Safety – July 2009 – Issue Number 32 Correspondence/Comments should be sent to the Pharmacovigilance Section, Irish Medicines Board, Kevin O’Malley House, Earlsfort Centre, Earlsfort Terrace, Dublin 2.

Source: http://iscp-live.s3.amazonaws.com/images/stories/cpd/drug_safety_32__final_3.pdf?javer=1201281240