Pharmacotherapeutic group: Combinations for the eradication of Helicobacter pylori, ATC code: A02BD08
Pylera is a triple fixed combination capsule containing bismuth subcitrate potassium, metronidazole and tetracycline hydrochloride for the eradication of H. pylori in combination with omeprazole (quadruple therapy).
Mechanism of action
Bismuth
The exact effect of bismuth in the treatment of H. pylori infections is still unknown. It appears to be related to direct toxicity on membrane function, inhibition of protein and cell wall synthesis, inhibition of urease enzyme activity, prevention of cytoadherence, ATP synthesis and a non-specific competitive interference with iron transport.
Metronidazole
The antimicrobial mechanism of action of metronidazole depends on the reduction of its nitro moiety by nitroreductase and other reductases to nitro anion radicals. These radicals damage the DNA of the bacteria, ultimately resulting in cell death.
Tetracycline
Tetracycline binds specifically to the 30S ribosome and prevents access of tRNA to mRNA-ribosome complex and thus interfere with protein synthesis.
Relationship between pharmacokinetics and pharmacodynamics
Bismuth
The PK/PD relationship of bismuth subcitrate has not been established.
Metronidazole
Efficacy is mainly dependent upon the Cmax (maximum serum concentration): MIC (minimum inhibitory concentration) ratio of the pathogen and the AUC (area under the curve): MIC ratio of the pathogen, respectively.
Tetracycline
Efficacy is mainly dependent upon the AUC (area under the curve): MIC ratio of the pathogen.
Mechanism(s) of resistance
Bismuth
Resistance to bismuth among Gram-negative bacteria has been shown to be dependent upon iron and its uptake. Resistance to the inhibitory action of bismuth is inversely related to iron concentration and strongly dependent on iron transport mechanisms.
Metronidazole
In Helicobacter pylori resistance is related to mutations of the NADPH-nitroreductase coding gene. These mutations prevent the reduction of the nitro moiety of metronidazole by the nitroreductase.
Tetracycline
The three main resistance mechanisms that have been described are:
| | • Decreased accumulation of tetracycline as a result of either decreased antibiotic influx or acquisition of an energy-dependent efflux pathway, |
| | • Decreased access of tetracycline to the ribosome because of the presence of ribosome protection proteins, and |
| | • Enzymatic inactivation of tetracyclines. |
There is a complete cross-resistance between metronidazole and other Imidazoles and between tetracycline and other tetracyclines.
Breakpoints
Bismuth
Species-related Breakpoints for bismuth and H. pylori have not been set by EUCAST (European Committee on Antimicrobial Susceptibility Testing).
Metronidazole
Testing of metronidazole is performed by using the usual dilution series. The following minimum inhibitory concentrations were determined for sensitive and resistant micro-organisms for metronidazole:
EUCAST Breakpoints:
| Species | Sensitive | Resistant |
| Helicobacter pylori | ≤ 4,0 mg/l | > 4,0 mg/l |
* based mainly on serum pharmacokinetics
Tetracycline
Species-related Breakpoints for tetracycline and H. pylori have not been set by EUCAST. However, a resistance breakpoint for tetracycline and H. pylori of 4 mg/l has been used.
Prevalence of acquired resistance
The prevalence of resistance varies geographically and with time for Helicobacter pylori. Data on the local resistance information are thus desirable, particularly in order to ensure adequate treatment of severe infections. If the local resistance situation puts the efficacy of Pylera in doubt, expert therapeutic advice should be sought. Particularly in cases of severe infection or unsuccessful therapy, a microbiological diagnosis with confirmation of the micro-organism and its sensitivity to the active ingredients of Pylera should be undertaken.
Currently, the resistance rate of Helicobacter pylori regarding tetracycline is considered to be less than 5% while the resistance rate regarding metronidazole lies between approximately 30% and 50%. Clinical data reveal a slight reduction of the eradication rate of H. pylori after treatment with Pylera in patients with metronidazole-resistant strains.
Clinical efficacy and safety
Two comparative trials have been conducted, one in Europe (pivotal) and one in the US (supportive), comparing Pylera in combination with omeprazole treatment for 10 days with the standard treatment regimen omeprazole, amoxicillin and clarithromycin (OAC) for 7 and 10 days, respectively. Both studies were randomized, parallel group, open label, active controlled, non-inferiority trials and included subjects with confirmed H. pylori infection. The results are summarised in the table below. Compliance was greater than 95% in both treatment groups in both studies.
In order to evaluate the impact of antibiotic resistance, biopsies were taken for culture and resistance of the bacterial strains to clarithromycin and metronidazole was tested. The minimum inhibitory concentration (MIC) defining sensitivity was ≤ 8 µg/ml for metronidazole and < 1 µg/ml for clarithromycin. The results indicate that Pylera is efficacious regardless of resistance of the bacterial strain to metronidazole or clarithromycin.
The impact of ulcers on treatment efficacy was also evaluated in the pivotal European study. The efficacy of Pylera was similar in those patients with presence or past history of peptic ulcers and those without.
| Eradication Rates in Controlled Studies using Pylera Capsules (ITT & PP) |
| | ITT/MITT | PP |
| Pivotal study for EU | Supportive study | Pivotal study for EU | Supportive study |
| Treatments | Pylera + Ome- prazole | OAC | Pylera + Ome- prazole | OAC | Pylera + Ome- prazole | OAC | Pylera + Ome- prazole | OAC |
| Treatment duration | 10 days | 7 days | 10 days | 10 days | 10 days | 7 days | 10 days | 10 days |
| Number evaluable for ITT/MITT/PP | 218 | 222 | 138 | 137 | 178 | 161 | 120 | 124 |
| Eradicated, n (%) | 174 (79.8%a 92.6%b) | 123 (55.4%a 67.6%b) | 121 (87.7%) | 114 (83.2%) | 166 (93.3%) | 112 (69.6%) | 111 (92.5%) | 108 (87.1%) |
| Eradication rates in patients with peptic ulcer | 18/20 (90.0%) | 18/29 (62.1%) | ND | ND | 18/19 (94.7%) | 15/18 (83.3%) | ND | ND |
| Eradication rates in non-ulcer dyspepsia | 155/196 (79.1%) | 103/189 (54.5%) | ND | ND | 147/158 (93.0%) | 95/141 (67.4%) | ND | ND |
| Eradication rates for: |
| Metronidazole resistant | 40/48 (83.3%) | 31/54 (57.4%) | 41/51 (80.4%) | ND | 38/42 (90.5%) | 28/41 (68.3%) | 38/44 (86.4%) | ND |
| Metronidazole sensitive | 101/123 (82.1%) | 70/120 (58.3%) | 68/74 (91.9%) | ND | 98/103 (95.1%) | 64/90 (71.7%) | 61/64 (95.3%) | ND |
| Clarithromycin resistant | 33/38 (86.8%) | 2/29 (6.9%) | ND | 3/14 (21.4%) | 30/33 (90.9%) | 2/25 (8.0%) | ND | 3/13 (23.1%) |
| Clarithromycin sensitive | 108/133 (81.2%) | 99/145 (68.3%) | ND | 93/101 (92.1%) | 106/112 (94.6%) | 90/106 (84.9%) | ND | 88/93 (94.6%) |
| ITT = Intent to treat. MITT = Modified intent to treat. ND = Not determined. PP = Per Protocol a Missing values imputed as non-eradication. b Observed cases analysis. |
Safety data from these trials are included in the pooled information in section 4.8.
Paediatric population
The European Medicines Agency has waived the obligation to conduct studies with Pylera in all subsets of the paediatric population on the grounds that the specific medicinal product is likely to be unsafe (see section 4.2 for information on paediatric use).