AZITHROMYCIN

Azithromycin for oral suspension USP contains the active ingredient azithromycin, USP, an azalide, a subclass of macrolide antibiotics, for oral administration. Azithromycin, USP has the chemical name (2R,3S,4R,5R,8R, 10R,11R,12S,13S,14R) -13-[(2,6-dideoxy-3- C -methyl-3- O -methyl-α- L-ribo- hexopyranosyl) oxy]-2-ethyl-3,4,10-trihydroxy-3,5,6,8,10,12,14-heptamethyl-11-[[3,4,6-trideoxy-3- (dimethylamino)-β- D-xylo -hexopyranosyl]oxy]-1-oxa-6-azacyclopentadecan-15-one. Azithromycin, USP is derived from erythromycin; however, it differs chemically from erythromycin in that a methyl-substituted nitrogen atom is incorporated into the lactone ring. Azithromycin, USP has the following structural formula: C 38 H 72 N 2 O 12 M.W. 749.0 Azithromycin, USP, as the monohydrate, is a white crystalline powder with a molecular formula of C 38 H 72 N 2 O 12 •H 2 O and a molecular weight of 767.0. Azithromycin for oral suspension USP is supplied in bottles containing azithromycin monohydrate powder equivalent to 300 mg, 600 mg, 900 mg or 1200 mg azithromycin, USP per bottle and the following inactive ingredients: ammonio methacrylate copolymer, banana flavor, cherry flavor, colloidal silicon dioxide, FD&C Red No. 40, hydroxypropyl cellulose, sucrose, tribasic sodium phosphate anhydrous, vanilla flavor, and xanthan gum. After constitution, each 5 mL of suspension contains 100 mg or 200 mg of azithromycin, USP. Chemical structure

Azithromycin for oral suspension USP is indicated for the treatment of patients with mild to moderate infections (pneumonia: see WARNINGS ) caused by susceptible strains of the designated microorganisms in the specific conditions listed below. As recommended dosages, durations of therapy and applicable patient populations vary among these infections, please see DOSAGE AND ADMINISTRATION for specific dosing recommendations. Adults Acute bacterial exacerbations of chronic obstructive pulmonary disease due to Haemophilus influenzae, Moraxella catarrhalis or Streptococcus pneumoniae. Acute bacterial sinusitis due to Haemophilus influenzae, Moraxella catarrhalis or Streptococcus pneumoniae . Community-acquired pneumonia due to Chlamydophila pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae or Streptococcus pneumoniae in patients appropriate for oral therapy. NOTE: Azithromycin should not be used in patients with pneumonia who are judged to be inappropriate for oral therapy because of moderate to severe illness or risk factors such as any of the following: patients with cystic fibrosis, patients with nosocomially acquired infections, patients with known or suspected bacteremia, patients requiring hospitalization, elderly or debilitated patients, or patients with significant underlying health problems that may compromise their ability to respond to their illness (including immunodeficiency or functional asplenia). Pharyngitis/tonsillitis caused by Streptococcus pyogenes as an alternative to first-line therapy in individuals who cannot use first-line therapy. NOTE: Penicillin by the intramuscular route is the usual drug of choice in the treatment of Streptococcus pyogenes infection and the prophylaxis of rheumatic fever. Azithromycin for oral suspension USP is often effective in the eradication of susceptible strains of Streptococcus pyogenes from the nasopharynx. Because some strains are resistant to azithromycin for oral suspension USP, susceptibility tests should be performed when patients are treated with azithromycin for oral suspension USP. Data establishing efficacy of azithromycin in subsequent prevention of rheumatic fever are not available. Uncomplicated skin and skin structure infections due to Staphylococcus aureus, Streptococcus pyogenes, or Streptococcus agalactiae. Abscesses usually require surgical drainage. Urethritis and cervicitis due to Chlamydia trachomatis or Neisseria gonorrhoeae . Genital ulcer disease in men due to Haemophilus ducreyi (chancroid). Due to the small number of women included in clinical trials, the efficacy of azithromycin in the treatment of chancroid in women has not been established. Azithromycin for oral suspension USP, at the recommended dose, should not be relied upon to treat syphilis. Antimicrobial agents used in high doses for short periods of time to treat non-gonococcal urethritis may mask or delay the symptoms of incubating syphilis. All patients with sexually-transmitted urethritis or cervicitis should have a serologic test for syphilis and appropriate cultures for gonorrhea performed at the time of diagnosis. Appropriate antimicrobial therapy and follow-up tests for these diseases should be initiated if infection is confirmed. Appropriate culture and susceptibility tests should be performed before treatment to determine the causative organism and its susceptibility to azithromycin, USP. Therapy with azithromycin for oral suspension USP may be initiated before results of these tests are known; once the results become available, antimicrobial therapy should be adjusted accordingly. To reduce the development of drug-resistant bacteria and maintain the effectiveness of azithromycin for oral suspension USP and other antibacterial drugs, azithromycin for oral suspension USP should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy. Pediatric Patients See PRECAUTIONS, Pediatric Use and CLINICAL STUDIES, Pediatric Patients. Acute otitis media caused by Haemophilus influenzae, Moraxella catarrhalis or Streptococcus pneumoniae. (For specific dosage recommendation, see DOSAGE AND ADMINISTRATION .) Community-acquired pneumonia due to Chlamydophila pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae or Streptococcus pneumoniae in patients appropriate for oral therapy. (For specific dosage recommendation, see DOSAGE AND ADMINISTRATION .) NOTE: Azithromycin should not be used in pediatric patients with pneumonia who are judged to be inappropriate for oral therapy because of moderate to severe illness or risk factors such as any of the following: patients with cystic fibrosis, patients with nosocomially acquired infections, patients with known or suspected bacteremia, patients requiring hospitalization, or patients with significant underlying health problems that may compromise their ability to respond to their illness (including immunodeficiency or functional asplenia). Pharyngitis/tonsillitis caused by Streptococcus pyogenes as an alternative to first-line therapy in individuals who cannot use first-line therapy. (For specific dosage recommendation, see DOSAGE AND ADMINISTRATION .) NOTE: Penicillin by the intramuscular route is the usual drug of choice in the treatment of Streptococcus pyogenes infection and the prophylaxis of rheumatic fever. Azithromycin for oral suspension USP is often effective in the eradication of susceptible strains of Streptococcus pyogenes from the nasopharynx. Because some strains are resistant to azithromycin for oral suspension USP, susceptibility tests should be performed when patients are treated with azithromycin for oral suspension USP. Data establishing efficacy of azithromycin in subsequent prevention of rheumatic fever are not available. Appropriate culture and susceptibility tests should be performed before treatment to determine the causative organism and its susceptibility to azithromycin. Therapy with azithromycin for oral suspension USP may be initiated before results of these tests are known; once the results become available, antimicrobial therapy should be adjusted accordingly.

See INDICATIONS AND USAGE and CLINICAL PHARMACOLOGY . Adults Infection DUE TO THE INDICATED ORGANISMS (see INDICATIONS AND USAGE ). Recommended Dose/Duration of Therapy Community-acquired pneumonia (mild severity) Pharyngitis/tonsillitis (second line therapy) Skin/skin structure (uncomplicated) 500 mg as a single dose on Day 1, followed by 250 mg once daily on Days 2 through 5. Acute bacterial exacerbations of chronic obstructive pulmonary disease (mild to moderate) 500 mg QD x 3 days OR 500 mg as a single dose on Day 1, followed by 250 mg once daily on Days 2 through 5. Acute bacterial sinusitis 500 mg QD x 3 days Genital ulcer disease (chancroid) One single 1 gram dose Non-gonococcal urethritis and cervicitis One single 1 gram dose Gonococcal urethritis and cervicitis One single 2 gram dose Renal Insufficiency No dosage adjustment is recommended for subjects with renal impairment (GFR ≤ 80 mL/min). The mean AUC 0-120 was similar in subjects with GFR 10 to 80 mL/min compared to subjects with normal renal function, whereas it increased 35% in subjects with GFR < 10 mL/min compared to subjects with normal renal function. Caution should be exercised when azithromycin is administered to subjects with severe renal impairment (see CLINICAL PHARMACOLOGY, Special Populations, Renal Insufficiency ). Hepatic Insufficiency The pharmacokinetics of azithromycin in subjects with hepatic impairment have not been established. No dose adjustment recommendations can be made in patients with impaired hepatic function (see CLINICALPHARMACOLOGY, Special Populations, Hepatic Insufficiency ). No dosage adjustment is recommended based on age or gender (see CLINICAL PHARMACOLOGY, Special Populations ). Pediatric Patients Azithromycin for oral suspension can be taken with or without food. Acute Otitis Media: The recommended dose of azithromycin for oral suspension for the treatment of pediatric patients with acute otitis media is 30 mg/kg given as a single dose or 10 mg/kg once daily for 3 days or 10 mg/kg as a single dose on the first day followed by 5 mg/kg/day on Days 2 through 5. (See chart below.) Acute Bacterial Sinusitis: The recommended dose of azithromycin for oral suspension for the treatment of pediatric patients with acute bacterial sinusitis is 10 mg/kg once daily for 3 days. (See chart below.) Community-Acquired Pneumonia: The recommended dose of azithromycin for oral suspension for the treatment of pediatric patients with community-acquired pneumonia is 10 mg/kg as a single dose on the first day followed by 5 mg/kg on Days 2 through 5. (See chart below.) PEDIATRIC DOSAGE GUIDELINES FOR OTITIS MEDIA, ACUTE BACTERIAL SINUSITIS AND COMMUNITY-ACQUIRED PNEUMONIA (Age 6 months and above, see PRECAUTIONS, Pediatric Use .) Based on Body Weight OTITIS MEDIA AND COMMUNITY-ACQUIRED PNEUMONIA: (5 Day Regimen) Effectiveness of the 3 day or 1 day regimen in pediatric patients with community-acquired pneumonia has not been established. Dosing Calculated on 10 mg/kg/day Day 1 and 5 mg/kg/day Days 2 to 5. Weight 100 mg/5 mL 200 mg/5 mL Total mL per Treatment Course Total mg per Treatment Course Kg Lbs. Day 1 Days 2 to 5 Day 1 Days 2 to 5 5 11 2.5 mL (½ tsp) 1.25 mL ( 1 / 4 tsp) 7.5 mL 150 mg 10 22 5 mL (1 tsp) 2.5 mL ( 1 / 2 tsp) 15 mL 300 mg 20 44 5 mL (1 tsp) 2.5 mL (½ tsp) 15 mL 600 mg 30 66 7.5 mL (1½ tsp) 3.75 mL (¾ tsp) 22.5 mL 900 mg 40 88 10 mL (2 tsp) 5 mL (1 tsp) 30 mL 1200 mg 50 and above 110 and above 12.5 mL (2½ tsp) 6.25 mL (1¼ tsp) 37.5 mL 1500 mg OTITIS MEDIA AND ACUTE BACTERIAL SINUSITIS: (3 Day Regimen) Effectiveness of the 5 day or 1 day regimen in pediatric patients with acute bacterial sinusitis has not been established. Dosing Calculated on 10 mg/kg/day. Weight 100 mg/5 mL 200 mg/5 mL Total mL per Treatment Course Total mg per Treatment Course Kg Lbs. Day 1 to 3 Day 1 to 3 5 11 2.5 mL (½ tsp) 7.5 mL 150 mg 10 22 5 mL (1 tsp) 15 mL 300 mg 20 44 5 mL (1 tsp) 15 mL 600 mg 30 66 7.5 mL (1½ tsp) 22.5 mL 900 mg 40 88 10 mL (2 tsp) 30 mL 1200 mg 50 and above 110 and above 12.5 mL (2½ tsp) 37.5 mL 1500 mg OTITIS MEDIA: (1 Day Regimen) Dosing Calculated on 30 mg/kg as a single dose. Weight 200 mg/5 mL Total mL per Treatment Course Total mg per Treatment Course Kg Lbs. Day 1 5 11 3.75 mL (¾ tsp) 3.75 mL 150 mg 10 22 7.5 mL (1½ tsp) 7.5 mL 300 mg 20 44 15 mL (3 tsp) 15 mL 600 mg 30 66 22.5 mL (4½ tsp) 22.5 mL 900 mg 40 88 30 mL (6 tsp) 30 mL 1200 mg 50 and above 110 and above 37.5 mL (7½ tsp) 37.5 mL 1500 mg The safety of re-dosing azithromycin in pediatric patients who vomit after receiving 30 mg/kg as a single dose has not been established. In clinical studies involving 487 patients with acute otitis media given a single 30 mg/kg dose of azithromycin, eight patients who vomited within 30 minutes of dosing were re-dosed at the same total dose. Pharyngitis/Tonsillitis: The recommended dose of azithromycin for oral suspension for children with pharyngitis/tonsillitis is 12 mg/kg once daily for 5 days. (See chart below.) PEDIATRIC DOSAGE GUIDELINES FOR PHARYNGITIS/TONSILLITIS (Age 2 years and above, see PRECAUTIONS, Pediatric Use .) Based on Body Weight PHARYNGITIS/TONSILLITIS: (5 Day Regimen) Dosing Calculated on 12 mg/kg/day for 5 days. Weight 200 mg/5 mL Total mL per Treatment Course Total mg per Treatment Course Kg Lbs. Day 1 to 5 8 18 2.5 mL (½ tsp) 12.5 mL 500 mg 17 37 5 mL (1 tsp) 25 mL 1000 mg 25 55 7.5 mL (1½ tsp) 37.5 mL 1500 mg 33 73 10 mL (2 tsp) 50 mL 2000 mg 40 88 12.5 mL (2½ tsp) 62.5 mL 2500 mg Constituting instructions for azithromycin for oral suspension, 300, 600, 900, 1200 mg bottles. The table below indicates the volume of water to be used for constitution: Amount of water to be added Total volume after constitution (azithromycin content) Azithromycin concentration after constitution 9 mL (300 mg) 15 mL (300 mg) 100 mg/5 mL 9 mL (600 mg) 15 mL (600 mg) 200 mg/5 mL 12 mL (900 mg) 22.5 mL (900 mg) 200 mg/5 mL 15 mL (1200 mg) 30 mL (1200 mg) 200 mg/5 mL Shake well before each use. Oversized bottle provides shake space. Keep tightly closed. After mixing, store suspension at 5° to 25°C (41° to 77°F) and use within 10 days. Discard after full dosing is completed.

Azithromycin is contraindicated in patients with known hypersensitivity to azithromycin, erythromycin any macrolide or ketolide antibiotic. Azithromycin is contraindicated in patients with a history of cholestatic jaundice/hepatic dysfunction associated with prior use of azithromycin.

In clinical trials, most of the reported side effects were mild to moderate in severity and were reversible upon discontinuation of the drug. Potentially serious side effects of angioedema and cholestatic jaundice were reported rarely. Approximately 0.7% of the patients (adults and pediatric patients) from the 5 day multiple-dose clinical trials discontinued azithromycin therapy because of treatment-related side effects. In adults given 500 mg/day for 3 days, the discontinuation rate due to treatment-related side effects was 0.6%. In clinical trials in pediatric patients given 30 mg/kg, either as a single dose or over 3 days, discontinuation from the trials due to treatment-related side effects was approximately 1% (see DOSAGE AND ADMINISTRATION ). Most of the side effects leading to discontinuation were related to the gastrointestinal tract, e.g., nausea, vomiting, diarrhea, or abdominal pain (see CLINICAL STUDIES, Pediatric Patients ). Clinical Adults Multiple-dose regimens: Overall, the most common treatment-related side effects in adult patients receiving multiple-dose regimens of azithromycin were related to the gastrointestinal system with diarrhea/loose stools (4 to 5%), nausea (3%) and abdominal pain (2 to 3%) being the most frequently reported. No other treatment-related side effects occurred in patients on the multiple-dose regimens of azithromycin with a frequency greater than 1%. Side effects that occurred with a frequency of 1% or less included the following: Cardiovascular: Palpitations, chest pain. Gastrointestinal: Dyspepsia, flatulence, vomiting, melena and cholestatic jaundice. Genitourinary: Monilia, vaginitis and nephritis. Nervous System: Dizziness, headache, vertigo and somnolence. General: Fatigue. Allergic: Rash, pruritus, photosensitivity and angioedema. Single 1 gram dose regimen: Overall, the most common side effects in patients receiving a single-dose regimen of 1 gram of azithromycin were related to the gastrointestinal system and were more frequently reported than in patients receiving the multiple-dose regimen. Side effects that occurred in patients on the single one-gram dosing regimen of azithromycin with a frequency of 1% or greater included diarrhea/loose stools (7%), nausea (5%), abdominal pain (5%), vomiting (2%), dyspepsia (1%) and vaginitis (1%). Single 2 gram dose regimen: Overall, the most common side effects in patients receiving a single 2 gram dose of azithromycin were related to the gastrointestinal system. Side effects that occurred in patients in this study with a frequency of 1% or greater included nausea (18%), diarrhea/loose stools (14%), vomiting (7%), abdominal pain (7%), vaginitis (2%), dyspepsia (1%) and dizziness (1%). The majority of these complaints were mild in nature. Pediatric Patients Single- and Multiple-dose regimens: The types of side effects in pediatric patients were comparable to those seen in adults, with different incidence rates for the dosage regimens recommended in pediatric patients. Acute Otitis Media: For the recommended total dosage regimen of 30 mg/kg, the most frequent side effects (≥ 1%) attributed to treatment were diarrhea, abdominal pain, vomiting, nausea and rash (see DOSAGE AND ADMINISTRATION and CLINICAL STUDIES, Pediatric Patients ). The incidence, based on dosing regimen, is described in the table below: Dosage Regimen Diarrhea, % Abdominal Pain, % Vomiting, % Nausea, % Rash, % 1 day 4.3% 1.4% 4.9% 1% 1% 3 day 2.6% 1.7% 2.3% 0.4% 0.6% 5 day 1.8% 1.2% 1.1% 0.5% 0.4% Community-Acquired Pneumonia: For the recommended dosage regimen of 10 mg/kg on Day 1 followed by 5 mg/kg on Days 2 to 5, the most frequent side effects attributed to treatment were diarrhea/loose stools, abdominal pain, vomiting, nausea and rash. The incidence is described in the table below: Dosage Regimen Diarrhea/Loose stools, % Abdominal Pain, % Vomiting, % Nausea, % Rash, % 5 day 5.8% 1.9% 1.9% 1.9% 1.6% Pharyngitis/tonsillitis: For the recommended dosage regimen of 12 mg/kg on Days 1 to 5, the most frequent side effects attributed to treatment were diarrhea, vomiting, abdominal pain, nausea and headache. The incidence is described in the table below: Dosage Regimen Diarrhea, % AbdominalPain, % Vomiting, % Nausea, % Rash, % Headache, % 5 day 5.4% 3.4% 5.6% 1.8% 0.7% 1.1% With any of the treatment regimens, no other treatment-related side effects occurred in pediatric patients treated with azithromycin with a frequency greater than 1%. Side effects that occurred with a frequency of 1% or less included the following: Cardiovascular: Chest pain. Gastrointestinal: Dyspepsia, constipation, anorexia, enteritis, flatulence, gastritis, jaundice, loose stools and oral moniliasis. Hematologic and Lymphatic: Anemia and leukopenia. Nervous System: Headache (otitis media dosage), hyperkinesia, dizziness, agitation, nervousness and insomnia. General: Fever, face edema, fatigue, fungal infection, malaise and pain. Allergic: Rash and allergic reaction. Respiratory: Cough increased, pharyngitis, pleural effusion and rhinitis. Skin and Appendages: Eczema, fungal dermatitis, pruritus, sweating, urticaria and vesiculobullous rash. Special Senses: Conjunctivitis. Postmarketing Experience Adverse events reported with azithromycin during the postmarketing period in adult and/or pediatric patients for which a causal relationship may not be established include: Allergic: Arthralgia, edema, urticaria and angioedema. Cardiovascular: Arrhythmias including ventricular tachycardia and hypotension. There have been rare reports of QT prolongation and torsade de pointes . Gastrointestinal: Anorexia, constipation, dyspepsia, flatulence, vomiting/diarrhea rarely resulting in dehydration, pseudomembranous colitis, pancreatitis, oral candidiasis, pyloric stenosis, and rare reports of tongue discoloration. General: Asthenia, paresthesia, fatigue, malaise and anaphylaxis (rarely fatal). Genitourinary: Interstitial nephritis and acute renal failure and vaginitis. Hematopoietic: Thrombocytopenia. Liver/Biliary: Adverse reactions related to hepatic dysfunction have been reported in postmarketing experience with azithromycin (see WARNINGS, Hepatotoxicity ). Nervous System: Convulsions, dizziness/vertigo, headache, somnolence, hyperactivity, nervousness, agitation and syncope. Psychiatric: Aggressive reaction and anxiety. Skin/Appendages: Pruritus, rarely serious skin reactions including erythema multiforme, Stevens-Johnson syndrome and toxic epidermal necrolysis. Special Senses: Hearing disturbances including hearing loss, deafness and/or tinnitus and reports of taste/smell perversion and/or loss. Laboratory Abnormalities Adults Clinically significant abnormalities (irrespective of drug relationship) occurring during the clinical trials were reported as follows: with an incidence of greater than 1%: decreased hemoglobin, hematocrit, lymphocytes, neutrophils and blood glucose; elevated serum creatine phosphokinase, potassium, ALT, GGT, AST, BUN, creatinine, blood glucose, platelet count, lymphocytes, neutrophils and eosinophils; with an incidence of less than 1%: leukopenia, neutropenia, decreased sodium, potassium, platelet count, elevated monocytes, basophils, bicarbonate, serum alkaline phosphatase, bilirubin, LDH and phosphate. The majority of subjects with elevated serum creatinine also had abnormal values at baseline. When follow-up was provided, changes in laboratory tests appeared to be reversible. In multiple-dose clinical trials involving more than 5000 patients, four patients discontinued therapy because of treatment-related liver enzyme abnormalities and one because of a renal function abnormality. Pediatric Patients One, Three and Five Day Regimens Laboratory data collected from comparative clinical trials employing two 3 day regimens (30 mg/kg or 60 mg/kg in divided doses over 3 days), or two 5 day regimens (30 mg/kg or 60 mg/kg in divided doses over 5 days) were similar for regimens of azithromycin and all comparators combined, with most clinically significant laboratory abnormalities occurring at incidences of 1 to 5%. Laboratory data for patients receiving 30 mg/kg as a single dose were collected in one single center trial. In that trial, an absolute neutrophil count between 500 to 1500 cells/mm 3 was observed in 10/64 patients receiving 30 mg/kg as a single dose, 9/62 patients receiving 30 mg/kg given over 3 days, and 8/63 comparator patients. No patient had an absolute neutrophil count < 500 cells/mm 3 (see DOSAGE AND ADMINISTRATION ). In multiple-dose clinical trials involving approximately 4700 pediatric patients, no patients discontinued therapy because of treatment-related laboratory abnormalities.

Coadministration of nelfinavir at steady-state with a single oral dose of azithromycin resulted in increased azithromycin serum concentrations. Although a dose adjustment of azithromycin is not recommended when administered in combination with nelfinavir, close monitoring for known side effects of azithromycin, such as liver enzyme abnormalities and hearing impairment, is warranted (see ADVERSE REACTIONS ). Although, in a study of 22 healthy men, a 5 day course of azithromycin did not affect the prothrombin time from a subsequently administered dose of warfarin, spontaneous postmarketing reports suggest that concomitant administration of azithromycin may potentiate the effects of oral anticoagulants. Prothrombin times should be carefully monitored while patients are receiving azithromycin and oral anticoagulants concomitantly. Drug interaction studies were performed with azithromycin and other drugs likely to be coadministered (see CLINICAL PHARMACOLOGY, Drug-Drug Interactions ). When used in therapeutic doses, azithromycin had a modest effect on the pharmacokinetics of atorvastatin, carbamazepine, cetirizine, didanosine, efavirenz, fluconazole, indinavir, midazolam, rifabutin, sildenafil, theophylline (intravenous and oral), triazolam, trimethoprim/sulfamethoxazole or zidovudine. Coadministration with efavirenz, or fluconazole had a modest effect on the pharmacokinetics of azithromycin. No dosage adjustment of either drug is recommended when azithromycin is coadministered with any of the above agents. Interactions with the drugs listed below have not been reported in clinical trials with azithromycin; however, no specific drug interaction studies have been performed to evaluate potential drug-drug interaction. Nonetheless, they have been observed with macrolide products. Until further data are developed regarding drug interactions when azithromycin and these drugs are used concomitantly, careful monitoring of patients is advised: Digoxin–elevated digoxin concentrations. Ergotamine or dihydroergotamine–acute ergot toxicity characterized by severe peripheral vasospasm and dysesthesia. Terfenadine, cyclosporine, hexobarbital and phenytoin concentrations.