RIFINAH Coated tablet Ref.[10703] Active ingredients: Isoniazid Rifampicin Rifampicin and Isoniazid

Rifinah is a combination of 2 drugs, each of which has been associated with liver dysfunction.

All tuberculosis patients should have pre-treatment measurements of liver function.

Adults treated for tuberculosis with Rifinah should have baseline measurements of hepatic enzymes, bilirubin, serum creatinine, a complete blood count and a platelet count (or estimate).

Patients should be seen at least monthly during therapy and should be questioned specifically about symptoms associated with adverse reactions.

All patients with abnormalities should have follow-up, including laboratory testing, if necessary. However, because there is a higher frequency of isoniazid-associated hepatitis among persons older than 35 years of age, a transaminase measurement should be obtained at baseline and at least monthly during therapy in this age group. Other factors associated with an increased risk of hepatitis include daily use of alcohol, chronic liver disease, intravenous drug use and being a black or Hispanic woman.

Paradoxical drug reaction

After initial improvement of tuberculosis under therapy with Rifinah, the symptoms may worsen again. In affected patients, clinical or radiological deterioration of existing tuberculous lesions or the development of new lesions have been detected. Such reactions have been observed within the first few weeks or months of initiation of tuberculosis therapy. Cultures are usually negative, and such reactions do not usually indicate treatment failure.

The cause of this paradoxical reaction is still unclear, but an exaggerated immune reaction is suspected as a possible cause. In case a paradoxical reaction is suspected, symptomatic therapy to suppress the exaggerated immune reaction should be initiated if necessary. Furthermore, continuation of the planned tuberculosis combination therapy is recommended.

Patients should be advised to seek medical advice immediately if their symptoms worsen. The symptoms that occur are usually specific to the affected tissues. Possible general symptoms include cough, fever, tiredness, breathlessness, headache, loss of appetite, weight loss or weakness (see section 4.8).

If the patient has no evidence of pre-existing liver disease and normal pre-treatment liver function, liver function tests need only be repeated if fever, vomiting, jaundice or other deterioration in the patient’s condition occurs.

Patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption or sucrase-isomaltase insufficiency should not take this medicine.

Severe, systemic hypersensitivity reactions, including fatal cases, such as Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome have been observed during treatment with anti-tuberculosis therapy (See section 4.8).

Rifinah should be discontinued if an alternative etiology for the signs and symptoms cannot be established.

Rifampicin

Rifampicin should be given under the supervision of a respiratory or other suitably qualified physician.

Patients with impaired liver function should only be given rifampicin in cases of necessity, and then with caution and under close medical supervision. In these patients, lower doses of rifampicin are recommended and careful monitoring of liver function, especially serum glutamic pyruvic transaminase (SGPT) and serum glutamic oxaloacetic transaminase (SGOT) should initially be carried out prior to therapy, weekly for two weeks, then every two weeks for the next six weeks. If signs of hepatocellular damage occur, rifampicin should be withdrawn.

Rifampicin should also be withdrawn if clinically significant changes in hepatic function occur. The need for other forms of antituberculosis therapy and a different regimen should be considered. Urgent advice should be obtained from a specialist in the management of tuberculosis. If rifampicin is re-introduced after liver function has returned to normal, liver function should be monitored daily.

In patients with impaired liver function, elderly patients, malnourished patients and possibly children under two years of age, caution is particularly recommended when instituting therapeutic regimens in which isoniazid is to be used concurrently with rifampicin.

In some patients, hyperbilirubinaemia can occur in the early days of treatment. This results from competition between rifampicin and bilirubin for hepatic excretion. An isolated report showing a moderate rise in bilirubin and/or transaminase level is not in itself an indication for interrupting treatment; rather the decision should be made after repeating the tests, noting trends in the levels and considering them in conjunction with the patient’s clinical condition.

Because of the possibility of immunological reaction including anaphylaxis (see section 4.8 Undesirable effects) occurring with intermittent therapy (less than 2 to 3 times per week) patients should be closely monitored. Patients should be cautioned against interruption of dosage regimens since these reactions may occur.

Severe cutaneous adverse reactions (SCARs) including Steven-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS), acute generalized exanthematous pustulosis (AGEP), which can be life-threatening or fatal, have been reported with a not known frequency in association with Rifinah treatment.

At the time of prescription patients should be advised of the signs and symptoms and monitored closely for skin reactions. It is important to note that early manifestations of hypersensitivity, such as fever, lymphadenopathy or biological abnormalities (including eosinophilia, liver abnormalities) may be present even though rash is not evident. If such signs or symptoms are present, the patient should be advised to consult immediately their physician. If signs and symptoms suggestive of these reactions appear, Rifinah should be withdrawn immediately and an alternative treatment considered (as appropriate).

Most of these reactions occurred within 2 days to 2 months after treatment initiation; the time to onset can vary depending on the conditions.

Rifampicin has enzyme induction properties that can enhance the metabolism of endogenous substrates including adrenal hormones, thyroid hormones and vitamin D. Isolated reports have associated porphyria exacerbation with rifampicin administration.

Rifampicin may produce a discoloration (yellow, orange, red, brown) of the teeth, urine, sweat, sputum and tears, and the patient should be forewarned of this. Soft contact lenses have been permanently stained (see section 4.8).

Rifampicin is a well characterized and potent inducer of drug metabolizing enzymes and transporters and might therefore decrease concomitant drug exposure and efficacy (see Section 4.5). Therefore, potential drug interactions should be considered whenever beginning or discontinuing rifampicin treatment.

Rifampicin may cause vitamin K dependent coagulopathy and severe bleeding (see Section 4.8). Monitoring of occurrence of coagulopathy is recommended for patients at particular bleeding risk. Supplemental vitamin K administration should be considered when appropriate (vitamin K deficiency, hypoprothrombinemia).

Isoniazid

Use of isoniazid should be carefully monitored in patients with current chronic liver disease or severe renal dysfunction.

Severe and sometimes fatal hepatitis associated with isoniazid therapy may occur and may develop even after many months of treatment. The risk of developing hepatitis is age related. Therefore, patients should be monitored for the prodromal symptoms of hepatitis, such as fatigue, weakness, malaise, anorexia, nausea or vomiting. If these symptoms appear or if signs suggestive of hepatic damage are detected, isoniazid should be discontinued promptly, since continued use of the drug in these cases has been reported to cause a more severe form of liver damage.

Cases of severe cutaneous reactions including Stevens-Johnson syndrome (SJS) and Toxic Epidermal Necrolysis (TEN), some with a fatal outcome, have been reported with the use of isoniazid (See section 4.8). Patients should be advised of the signs and symptoms and monitored closely for skin reactions. If signs or symptoms of SJS or TEN (e.g. progressive skin rash often with blisters or mucosal lesions) develops, the patient should be advised to consult immediately their physician. Isoniazid should be permanently discontinued if an alternative etiology for the signs and symptoms cannot be established.

Care should be exercised in the treatment of elderly or malnourished patients who may also require vitamin B6 supplementation with the isoniazid therapy.

Use of isoniazid should be carefully monitored in patients with slow acetylator status, epilepsy, history of psychosis, history of peripheral neuropathy, diabetes, alcohol dependence, HIV infection or porphyria.

Excipients

Sucrose

Patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption or sucrase-isomaltase insufficiency should not take this medicine.

Sodium

This medicine contains less than 1 mmol sodium (23 mg) per daily dose, that is to say essentially ‘sodium-free’.

Interference with laboratory and diagnostic tests

Therapeutic levels of rifampicin have been shown to inhibit standard microbiological assays for serum folate and Vitamin B12. Thus, alternative assay methods should be considered. Transient elevation of BSP and serum bilirubin has been reported. Rifampicin may impair biliary excretion of contrast media used for visualization of the gallbladder, due to competition for biliary excretion. Therefore, these tests should be performed before the morning dose of rifampicin.

Interactions with Other Medicinal Products

When Rifinah is given concomitantly with the combination saquinavir/ritonavir, the potential for hepatotoxicity is increased. Therefore, concomitant use of Rifinah with saquinavir/ritonavir is contraindicated (see section 4.3).

Cytochrome P-450 enzyme interaction

Rifampicin is known to induce, and isoniazid is known to inhibit certain cytochrome P-450 enzymes. In general, the impact of the competing effects of rifampicin and isoniazid on the metabolism of drugs that undergo biotransformation through the affected pathways is unknown. Therefore, caution should be used when prescribing Rifinah with drugs metabolised by cytochrome P-450. To maintain optimum therapeutic blood levels, dosages of drugs metabolised by these enzymes may require adjustment when starting or stopping Rifinah.

Interactions with Rifampicin

Pharmacodynamic Interactions

The potential for hepatotoxicity is increased with an anaesthetic.

When rifampicin is given concomitantly with either halothane or isoniazid, the potential for hepatotoxicity is increased. The concomitant use of rifampicin and halothane should be avoided. Patients receiving both rifampicin and isoniazid should be monitored closely for hepatotoxicity.

The concomitant use of rifampicin with other antibiotics causing vitamin K dependent coagulopathy such as cefazolin (or other cephalosporins with N-methyl-thiotetrazole side chain) should be avoided as it may lead to severe coagulation disorders, which may result in fatal outcome (specially with high doses).

Effect of rifampicin on other medicinal products

Induction of Drug Metabolizing Enzymes and Transporters

Rifinah is a well characterized and potent inducer of drug metabolizing enzymes and transporters. Enzymes and transporters reported to be affected by Rifinah include cytochromes P450 (CYP) 1A2, 2B6, 2C8, 2C9, 2C19, and 3A4, UDP-glucuronyltransferases (UGT), sulfotransferases, carboxylesterases, and transporters including P-glycoprotein (Pgp) and multidrug resistance-associated protein 2 (MRP2). Most drugs are substrates for one or more of these enzyme or transporter pathways, and these pathways may be induced by Rifinah simultaneously. Therefore, Rifinah may accelerate the metabolism and decrease the activity of certain co-administered drugs, or increase the activity of a coadministered pro-drug (where metabolic activation is required), and has the potential to perpetuate clinically important drug-drug interactions against many drugs and across many drug classes (Table 1). To maintain optimum therapeutic blood levels, dosages of drugs may require adjustment when starting or stopping concomitantly administered Rifinah.

Examples of drugs or drug classes affected by Rifinah:

• Antiarrhythmics (e.g. disopyramide, mexiletine, quinidine, propafenone, tocainide)
• Antiepileptics (e.g. phenytoin)
• Hormone antagonist (anti-oestrogens e.g. tamoxifen, toremifene, gestinone)
• Antipsychotics (e.g. haloperidol, aripiprazole)
• Anticoagulants (e.g. coumarins)
• Antifungals (e.g. fluconazole, itraconazole, ketoconazole, voriconazole)
• Antivirals (e.g. saquinavir, indinavir, efavirenz, amprenavir, nelfinavir, atazanavir, lopinavir, nevirapine)
• Barbiturates
• Beta-blockers (e.g. bisoprolol, propanolol)
• Anxiolytics and hypnotics (e.g. diazepam, benzodiazepines, zopiclone, zolpidem)
• Calcium channel blockers (e.g. diltiazem, nifedipine, verapamil, nimodipine, isradipine, nicardipine, nisoldipine)
• Anti-bacterials (e.g. chloramphenicol, clarithromycin, dapsone, doxycycline, fluoroquinolones, telithromycin)
• Corticosteroids
• Cardiac glycosides (e.g. digitoxin, digoxin)
• Clofibrate
• Immunosuppressive agents (e.g. ciclosporin, sirolimus, tacrolimus)
• Irinotecan
• Thyroid hormone (e.g. levothyroxine)
• Losartan
• Analgesics (e.g. methadone, narcotic analgesics)
• Praziquantel
• Quinine
• Riluzole
• Selective 5-HT3 receptor antagonists (e.g. ondansetron)
• Statins metabolised by CYP 3A4 (e.g. simvastatin)
• Theophylline
• Tricyclic antidepressants (e.g. amitriptyline, nortriptyline)
• Cytotoxics (e.g. imatinib)
• Diuretics (e.g. eplerenone)

Enalapril: Decrease enalapril active metabolite exposure. Dosage adjustments should be made if indicated by the patient’s clinical condition.

Hepatitis-C antiviral drugs (e.g. daclatasvir, simeprevir, sofosbuvir, telaprevir): Concurrent use of treatment of hepatitis-C antiviral drugs and rifampicin should be avoided.

Morphine: Plasma concentrations of morphine may be reduced by rifampicin. The analgesic effect of morphine should be monitored, and doses of morphine adjusted during and after treatment with rifampicin.

Clopidogrel: Increases active metabolite exposure. Rifinah strongly induces CYP2C19, resulting in both an increased level of clopidogrel active metabolite and platelet inhibition, which in particular might potentiate the risk of bleeding. As a precaution, concomitant use of clopidogrel and rifampicin should be discouraged.

Dapsone: Rifampicin has also been shown to increase the clearance of dapsone and the production of the hydroxylamine metabolite of dapsone which could increase the risk of methaemoglobinaemia, haemolytic anaemia, agranulocytosis, and haemolysis.

Systemic hormonal contraceptives including oestrogens and progestogens: Rifampicin treatment reduces the systemic exposure of oral contraceptives. Patients using oral contraceptives should be advised to change to non-hormonal methods of birth control during Rifinah therapy.

Antidiabetic (e.g. chlorpropamide, tolbutamide, sulfonylureas, rosiglitazone): diabetes may become more difficult to control.

If p-aminosalicylic acid and rifampicin are both included in the treatment regimen, they should be given not less than eight hours apart to ensure satisfactory blood levels.

Effect of other medicinal products on rifampicin

Antacids: Concomitant antacid administration may reduce the absorption of rifampicin.

Daily doses of rifampicin should be given at least 1 hour before the ingestion of antacids.

Paracetamol: Concomitant use of paracetamol with rifampicin may increase the risk of hepatotoxicity.

Other drug interactions with rifampicin

When the two drugs were taken concomitantly, decreased concentrations of atovaquone and increased concentrations of rifampicin were observed.

Interactions with Isoniazid

The following drugs may interact with isoniazid:

• Antiepileptics (e.g. carbamazepine and phenytoin).

There may be an increased risk of distal sensory neuropathy when isoniazid is used in patients taking stavudine.

Concomitant use of zalcitabine with isoniazid has been shown to approximately double the renal clearance if isoniazid in HIV infected patients.

Administration of prednisolone 20 mg to 13 slow acetylators and 13 fast acetylators for receiving isoniazid 10 mg/kg reduced plasma concentrations of isoniazid by 25% and 40%, respectively. The clinical significance of this effect has not been established.

The effect of acute alcohol intake (serum levels 1 g/L maintained for 12 hours) on the metabolism of isoniazid (300 mg/d for 2 days) was studies in 10 healthy volunteers in a controlled cross over design. The metabolism of isoniazid and its metabolite, acetyl isoniazid, was not modified by this acute alcohol intake. The metabolism of isoniazid may be increased in chronic alcoholics; however, this effect has not been quantified.

Appropriate adjustments of these drugs should be made.

Other interactions

Para-aminosalicylic acid may increase the plasma concentration and elimination half-life of isoniazid by competing for acetylating enzymes.

General anaesthetics may increase the hepatotoxicity of isoniazid.

The absorption of isoniazid is reduced by antacids.

The risk of CNS toxicity is increased when isoniazid is given with cycloserine.

Isoniazid may reduce plasma concentration of ketoconazole and increase plasma concentration of theophylline.

Food Interaction

Isoniazid is an inhibitor of monoamine oxidase (MAO) and diamine oxidase (DAO), therefore can reduce tyramine and histamine metabolism, causing symptoms such as headache, sweating, palpitations, flushing, and hypotension. Patients should be advised against ingesting foods rich in tyramine and/or histamine during treatment with isoniazid, such as cured meat, some cheeses (e.g. matured cheeses), wine, beer and some fish (e.g. tuna, mackerel, salmon).

Pregnancy

Rifampicin

Rifampicin has been shown to be teratogenic in rodents when given in large doses. There are no well controlled studies with Rifinah in pregnant women. Although rifampicin has been reported to cross the placental barrier and appear in cord blood, the effect of rifampicin, alone or in combination with other antituberculosis drugs, on the human foetus is not known.

When administered during the last few weeks of pregnancy, rifampicin can cause post-natal haemorrhages in the mother and infant, for which treatment with Vitamin K₁ may be indicated.

Isoniazid

It has been reported that in both rats and rabbits, isoniazid may exert an embryocardial effect when administered orally during pregnancy, although no isoniazid-related congenital anomalies have been found in reproduction studies in mammalian species (mice, rats, rabbits).

Therefore, Rifinah should be used in pregnant women or in women of child bearing potential only if the potential benefit justifies the potential risk to the foetus.

Lactation

Rifampicin and isoniazid are excreted in breast milk and infants should not be breast fed by a patient receiving Rifinah unless in the physician’s judgement the potential benefit to the patient outweighs the potential risk to the infant.

In breast-fed infants whose mothers are taking isoniazid, there is a theoretical risk of convulsions and neuropathy (associated with vitamin B6 deficiency), therefore they should be monitored for early signs of these effects and consideration should be given to treating both mother and infant prophylactically with pyridoxine.

Isoniazid has been associated with vertigo, visual disorders and psychotic reactions (see section 4.8). Patients should be informed of these, and advised that if affected, they should not drive, operate machinery or take part in any activities where these symptoms may put either themselves or others at risk.

The following CIOMS frequency rating is used, when applicable: Very common (≥1/10); Common (≥1/100 to <1/ 10); Uncommon (≥1/1,000 to <1/100); Rare (≥1/10,000 to <1/1,000); Very rare (<1/10,000), not known (cannot be estimated from available data).

Rifampicin

Reactions to rifampicin occurring with either daily or intermittent dosage regimens include:

^* Incidence of paradoxical drug reaction: Lower frequency is reported as 9.2% (53/573) (data between October 2007 and March 2010) and higher frequency is reported as 25% (19/76) (data between 2000 and 2010).

Isoniazid

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via Yellow Card Scheme at: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.

Not applicable.