Influence of an antacid containing aluminum and magnesium on the pharmacokinetics of cefixime

Do dietary interventions exert clinically important effects on the bioavailability of β-lactam antibiotics? A systematic review with meta-analyses

BACKGROUND

Managing drug-food interactions may help to achieve the optimal action and safety profile of β-lactam antibiotics.

METHODS

We conducted a systematic review with meta-analyses in adherence to PRISMA guidelines for 32 β-lactams. We included 166 studies assessing the impact of food, beverages, antacids or mineral supplements on the pharmacokinetic (PK) parameters or PK/pharmacodynamic (PK/PD) indices.

RESULTS

Eighteen of 25 β-lactams for which data on food impact were available had clinically important interactions. We observed the highest negative influence of food (AUC or Cmax decreased by >40%) for ampicillin, cefaclor (immediate-release formulations), cefroxadine, cefradine, cloxacillin, oxacillin, penicillin V (liquid formulations and tablets) and sultamicillin, whereas the highest positive influence (AUC or Cmax increased by >45%) for cefditoren pivoxil, cefuroxime and tebipenem pivoxil (extended-release tablets). Significantly lower bioavailability in the presence of antacids or mineral supplements occurred for 4 of 13 analysed β-lactams, with the highest negative impact for cefdinir (with iron salts) and moderate for cefpodoxime proxetil (with antacids). Data on beverage impact were limited to 11 antibiotics. With milk, the extent of absorption was decreased by >40% for cefalexin, cefradine, penicillin G and penicillin V, whereas it was moderately increased for cefuroxime. No significant interaction occurred with cranberry juice for two tested drugs (amoxicillin and cefaclor).

CONCLUSIONS

Factors such as physicochemical features of antibiotics, drug formulation, type of intervention, and patient's health state may influence interactions. Due to the poor actuality and diverse methodology of included studies and unproportionate data availability for individual drugs, we judged the quality of evidence as low.

Clinical pharmacokinetic of cefixime: a systematic review

Cefixime is an antibiotic from the cephalosporin class used to treat various bacterial infections. The purpose of performing this review is to thoroughly evaluate the pharmacokinetic (PK) data on cefixime.Five databases were systematically searched to identify studies on the PK of cefixime.A total of 38 articles meeting the eligibility criteria were included that provide data on concentration-time profiles or PK parameters such as peak plasma and serum concentration (C_max), area under the curve (AUC), clearance (CL), and time to reach C_max (t_max). A dose-dependent increase in AUC and Cmax of cefixime was depicted in healthy volunteers. The clearance of cefixime decreased according to the degree of renal insufficiency among haemodialysis patients. A significant difference in CL was found in comparing fasted and fed states. A biphasic decline in serum concentrations of cefixime was reported when it was taken without probenecid.This review compiles all the reports on the PK of cefixime in healthy and renally impaired patients; the summarized information can be used to optimize cefixime dosing in different disease states. Moreover, cefixime has increased time above MIC value suggesting that it may be an effective treatment for infections caused by certain pathogens.

Clinically significant drug interactions with antacids: an update

One may consider that drug-drug interactions (DDIs) associated with antacids is an obsolete topic because they are prescribed less frequently by medical professionals due to the advent of drugs that more effectively suppress gastric acidity (i.e. histamine H(2)-receptor antagonists [H2RAs] and proton pump inhibitors [PPIs]). Nevertheless, the use of antacids by ambulant patients may be ever increasing, because they are freely available as over-the-counter (OTC) drugs. Antacids consisting of weak basic substances coupled with polyvalent cations may alter the rate and/or the extent of absorption of concomitantly administered drugs via different mechanisms. Polyvalent cations in antacid formulations may form insoluble chelate complexes with drugs and substantially reduce their bioavailability. Clinical studies demonstrated that two classes of antibacterials (tetracyclines and fluoroquinolones) are susceptible to clinically relevant DDIs with antacids through this mechanism. Countermeasures against this type of DDI include spacing out the dosing interval - taking antacid either 4 hours before or 2 hours after administration of these antibacterials. Bisphosphonates may be susceptible to DDIs with antacids by the same mechanism, as described in the prescription information of most bisphosphonates, but no quantitative data about the DDIs are available. For drugs with solubility critically dependent on pH, neutralization of gastric fluid by antacids may alter the dissolution of these drugs and the rate and/or extent of their absorption. However, the magnitude of DDIs elicited by antacids through this mechanism is less than that produced by H2RAs or PPIs; therefore, the clinical relevance of such DDIs is often obscure. Magnesium ions contained in some antacid formulas may increase gastric emptying, thereby accelerating the rate of absorption of some drugs. However, the clinical relevance of this is unclear in most cases because the difference in plasma drug concentration observed after dosing shortly disappears. Recent reports have indicated that some of the molecular-targeting agents such as the tyrosine kinase inhibitors dasatinib and imatinib, and the thrombopoietin receptor agonist eltrombopag may be susceptible to DDIs with antacids. Finally, the recent trend of developing OTC drugs as combination formulations of an antacid and an H2RA is a concern because these drugs will increase the risk of DDIs by dual mechanisms, i.e. a gastric pH-dependent mechanism by H2RAs and a cation-mediated chelation mechanism by antacids.

Lack of pharmacokinetic interaction between linezolid and antacid in healthy volunteers

Several antibiotics show significant pharmacokinetic interactions when they are given orally concomitantly with antacids. The objective of this study was to evaluate the effects of antacid (containing magnesium) on the pharmacokinetics of linezolid. A single dose of 600 mg linezolid was given orally alone and 10 min after administration of the antacid Maalox 70mVal, which contains 600 mg magnesium hydroxide and 900 mg aluminum hydroxide, to nine healthy males and nine healthy females in a crossover and randomized study. Linezolid plasma concentrations were determined by high-performance liquid chromatography, and pharmacokinetic parameters were calculated for both treatments. Coadministration with antacids did not change the pharmacokinetics of linezolid. The ratios (90% confidence intervals) of the individual values of the area under the concentration-time curve and the maximum concentration in plasma (C(max)) (linezolid plus antacid versus linezolid alone) were 1.01 (0.99 to 1.02) and 0.99 (0.96 to 1.02), respectively. Likewise, no significant difference in any of the other pharmacokinetic parameters was observed between the treatment groups (the time to C(max), lag time, volume of distribution [V/F], and clearance [CL/F]). However, a significant sex difference was observed for AUC, C(max), V/F, and CL/F; and these differences could be almost completely explained by the differences in body weight between males and females. No clinically relevant adverse effects were detected under either condition. The coadministration of antacids had no effect on the pharmacokinetics of linezolid. This demonstrates that the oral absorption of linezolid was not affected by the presence of antacids containing magnesium hydroxide and aluminum hydroxide. Antacids can be safely administered together with linezolid.

Drug interactions with antacids. Mechanisms and clinical significance

Concomitant use of antacid preparations with other medications is common. The potential for antacid-drug interactions is dependent upon the chemistry and physical properties of the antacid preparation. The intragastric release of free aluminum and magnesium ions has potent effects on gastrointestinal function and on drug pharmacokinetics. Antacid-drug interactions may occur secondary to changes in gastrointestinal motility or alterations in gastric and urinary pH. Direct adsorption also results in decreased drug bioavailability. Human drug interaction studies are usually performed with healthy volunteers; extrapolation of these results to clinical situations may not always be valid. However, the current literature would suggest that significant interactions with antacids do occur with certain members of the quinolone, nonsteroidal anti-inflammatory drug (NSAID) and cephalosporin classes of drugs. Notable interactions also occur with tetracycline, quinidine, ketoconazole and oral glucocorticoids. These interactions are particularly relevant in the patient with sepsis, cardiac disease or inflammatory syndromes.

Effect of antacid on the bioavailability of cefprozil

The effect of antacid on the bioavailability of cefprozil was investigated in a two-way crossover study. Eight healthy male subjects received a single 500-mg oral dose of cefprozil with and without coadministration of 30 ml of an antacid suspension containing magnesium hydroxide and aluminum hydroxide (Maalox). Cefprozil consists of cis and trans isomers in an approximate 90:10 ratio. When cefprozil was administered alone (treatment A), the mean maximum concentrations (Cmax) of the cis and trans isomers were 9.2 and 1.2 micrograms/ml, respectively. When cefprozil was coadministered with Maalox (treatment B), the Cmax values of the cis and trans isomers were 8.7 and 1.3 micrograms/ml, respectively. The mean values of the area under the curve from time zero to infinity (AUC0-infinity) were 27.7 and 3.5 micrograms.h/ml for treatment A and 27.5 and 3.5 micrograms.h/ml for treatment B for the cis and trans isomers, respectively. The other pharmacokinetic parameters, time to Cmax, elimination half-life, mean residence time, renal clearance, and percent urinary excretion, were essentially the same for the two isomers. The respective values of the elimination half-life for the cis and trans isomers were 1.36 and 1.32 h for treatment A and 1.36 and 1.42 h for treatment B. Mean urinary excretion was 63 and 60% for treatment A and 58 and 56% for treatment B for the cis and trans isomers, respectively. No significant differences between the two treatments were found for any of the pharmacokinetic parameters for either isomer. For the cis isomer, bioavailability point estimates (90% confidence intervals) of the mean Cmax and AUG0-infinity values for the Maalox treatment relative to those for the reference treatment were 95% (87%, 103%) and 99% (95%, 104%), respectively. For the trans isomer, the value were 109% (92%, 126%) for Cmax and 97% (88%, 106%) for AUC0-infinity. On the basis of the results of this study, it is concluded that the bioavailability of cefprozil is not affected by the coadministration of Maalox.

Cefixime

Cefixime is a new orally active third-generation cephalosporin with a broad spectrum of activity against a variety of both gram-positive and -negative bacteria including many beta-lactamase-producing strains of streptococci, Haemophilus influenzae, Neisseria gonorrhoeae, and the majority of the Enterobacteriaceae. Activity of cefixime against Staphylococcus aureus, enterococci, Listeria monocytogenes, and Pseudomonas spp. is poor. The relatively long elimination half-life of cefixime (approximately 3.0 h) has made possible once- to twice-daily administration with the potential added benefit of improved patient compliance. Clinical trials indicate that cefixime is at least as effective as standard agents in the treatment of genitourinary and upper respiratory tract infections. The incidence of resistant organisms reported during clinical trials with cefixime was low. Adverse reactions observed during clinical trials were relatively uncommon and generally mild and transient in nature. The most significant adverse reactions reported were diarrhea and stool changes occurring in up to 20 percent of patients.