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Drug Interactions between Elixophyllin KI and Lexxel

This report displays the potential drug interactions for the following 2 drugs:

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Major

enalapril potassium iodide

Applies to: Lexxel (enalapril / felodipine) and Elixophyllin KI (potassium iodide / theophylline)

MONITOR CLOSELY: Concomitant use of angiotensin converting enzyme (ACE) inhibitors and potassium salts may increase the risk of hyperkalemia. Inhibition of ACE results in decreased aldosterone secretion, which in turn causes potassium retention. In one report, a significant increase in serum potassium level (3.88 +/- 0.41 to 4.84 +/- 0.45 mEq/L) was observed within one or two days following the addition of captopril in five patients who were treated with regimens that included potassium supplements or potassium-sparing diuretics. Three patients had laboratory-diagnosed hyperkalemia, including one patient receiving potassium supplementation who had a 66% increase in serum potassium. Levels remained elevated until potassium supplementation or captopril therapy was reduced or discontinued. In a postmarketing survey of patients who were prescribed enalapril in England between April and December 1985, researchers identified ten cases where enalapril appeared to have contributed to a deterioration in renal function and subsequent death. All ten patients had hyperkalemia, and seven were also receiving moderate to high dosages of potassium-sparing diuretics and/or potassium supplements. Hyperkalemia was felt to be the immediate cause of death in two of them. Risk factors for developing severe or life-threatening hyperkalemia may include renal impairment, diabetes, old age, severe or worsening heart failure, dehydration, and concomitant use of other agents that block the renin-angiotensin-aldosterone system or otherwise increase serum potassium levels.

MANAGEMENT: Caution is advised if ACE inhibitors must be used concurrently with potassium salts, particularly in patients with renal impairment, diabetes, old age, severe or worsening heart failure, dehydration, or concomitant therapy with other agents that increase serum potassium such as nonsteroidal anti-inflammatory drugs, beta-blockers, cyclosporine, heparin, tacrolimus, trimethoprim, and licorice. The combination should generally be avoided in these patients unless absolutely necessary and the benefits outweigh the potential risks. Serum potassium and renal function should be checked prior to initiating therapy and regularly thereafter. Patients should be given counseling on the appropriate levels of potassium and fluid intake, and advised to seek medical attention if they experience signs and symptoms of hyperkalemia such as nausea, vomiting, weakness, listlessness, tingling of the extremities, paralysis, confusion, weak pulse, and a slow or irregular heartbeat.

References

  1. Speirs CJ, Dollery CT, Inman WH, et al. (1988) "Postmarketing surveillance of enalapril II: investigation of the potential role of enalapril in deaths with renal failure." Br Med J, 297, p. 830-2
  2. Packer M, Lee WH (1986) "Provocation of hyper- and hypokalemic sudden death during treatment with and withdrawal of converting-enzyme inhibition in severe chronic congestive heart failure." Am J Cardiol, 57, p. 347-8
  3. Burnakis TG, Mioduch HJ (1984) "Combined therapy with captopril and potassium supplementation: a potential for hyperkalemia." Arch Intern Med, 144, p. 2371-2
  4. Warren SE, O'Connor DT (1980) "Hyperkalemia resulting from captopril administration." JAMA, 244, p. 2551-2
  5. Chan TY, Critchley JA (1992) "Life-threatening hyperkalaemia in an elderly patient receiving captopril, furosemide (frusemide) and potassium supplements." Drug Saf, 7, p. 159-61
  6. Walmsley RN, White GH, Cain M, McCarthy PJ, Booth J (1984) "Hyperkalemia in the elderly." Clin Chem, 30, p. 1409-12
  7. Stoltz ML, Andrews CE Jr (1990) "Severe hyperkalemia during very-low-calorie diets and angiotensin converting enzyme use ." JAMA, 264, p. 2737-8
  8. Ponce SP, Jennings AE, Madias NE, Harrington JT (1985) "Drug-induced hyperkalemia." Medicine (Baltimore), 64, p. 357-70
  9. Lawson DH, O'Connor PC, Jick H (1982) "Drug attributed alterations in potassium handling in congestive cardiac failure." Eur J Clin Pharmacol, 23, p. 21-5
  10. Lawson DH (1974) "Adverse reactions to potassium chloride." Q J Med, 43, p. 433-40
  11. (2001) "Product Information. K-Dur (potassium chloride)." Schering Corporation
  12. Good CB, McDermott L (1995) "Diet and serum potassium in patients on ACE inhibitors." JAMA, 274, p. 538
  13. Graves JW (1998) "Hyperkalemia due to a potassium-based water softener." N Engl J Med, 339, p. 1790-1
  14. Obialo CI, Ofili EO, Mirza T (2002) "Hyperkalemia in congestive heart failure patients aged 63 to 85 years with subclinical renal disease." Am J Cardiol, 90, p. 663-5
  15. Atlas SA, Case DB, Sealey JE, Laragh JH, McKinstry DN (1979) "Interruption of the renin-angiotensin system in hypertensive patients by captopril induces sustained reduction in aldosterone secretion, potassium retention and natriuresis." Hypertension, 1, p. 279-80
  16. Schuna AA, Schmidt GR, Pitterle ME (1986) "Serum potassium concentrations after initiation of captopril therapy." Clin Pharm, 5, p. 920-3
  17. Jarman PR, Mather HM (2003) "Diabetes may be independent risk factor for hyperkalaemia." BMJ, 327, p. 812
  18. Ray K, Dorman S, Watson R (1999) "Severe hyperkalaemia due to the concomitant use of salt substitutes and ACE inhibitors in hypertension: a potentially life threatening interaction." J Hum Hypertens, 13, p. 717-20
  19. Reardon LC, Macpherson DS (1998) "Hyperkalemia in outpatients using angiotensin-converting enzyme inhibitors. How much should we worry?" Arch Intern Med, 158, p. 26-32
  20. Perazella MA (2000) "Drug-induced hyperkalemia: old culprits and new offenders." Am J Med, 109, p. 307-14
  21. Jarman PR, Kehely AM, Mather HM (1995) "Hyperkalaemia in diabetes: prevalence and associations." Postgrad Med J, 71, p. 551-2
  22. Perazella MA, Mahnensmith RL (1997) "Hyperkalemia in the elderly: drugs exacerbate impaired potassium homeostasis." J Gen Intern Med, 12, p. 646-56
  23. Schoolwerth AC, Sica DA, Ballermann BJ, Wilcox CS, Council on the Kidney in Cardiovascular Disease and the Council for High Blood Pressure Research of the American Heart Association (2001) "Renal considerations in angiotensin converting enzyme inhibitor therapy: a statement for healthcare professionals from the Council on the Kidney in Cardiovascular Disease and the Council for High Blood Pressure Research of the American Heart Association." Circulation, 104, p. 1985-91
  24. Large DM, Carr PH, Laing I, Davies M (1984) "Hyperkalaemia in diabetes mellitus--potential hazards of coexisting hyporeninaemic hypoaldosteronism." Postgrad Med J, 60, p. 370-3
View all 24 references

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Minor

enalapril felodipine

Applies to: Lexxel (enalapril / felodipine) and Lexxel (enalapril / felodipine)

Calcium channel blockers and angiotensin converting enzyme (ACE) inhibitors may have additive hypotensive effects. While these drugs are often safely used together, careful monitoring of the systemic blood pressure is recommended during coadministration, especially during the first one to three weeks of therapy.

References

  1. Kaplan NM (1991) "Amlodipine in the treatment of hypertension." Postgrad Med J, 67 Suppl 5, s15-9
  2. DeQuattro V (1991) "Comparison of benazepril and other antihypertensive agents alone and in combination with the diuretic hydrochlorothiazide." Clin Cardiol, 14, iv28-32;
  3. Sun JX, Cipriano A, Chan K, John VA (1994) "Pharmacokinetic interaction study between benazepril and amlodipine in healthy subjects." Eur J Clin Pharmacol, 47, p. 285-9
  4. Di Somma S, et al. (1992) "Antihypertensive effects of verapamil, captopril and their combination at rest and during dynamic exercise." Arzneimittelforschung, 42, p. 103
View all 4 references

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Minor

theophylline felodipine

Applies to: Elixophyllin KI (potassium iodide / theophylline) and Lexxel (enalapril / felodipine)

In one study, concurrent administration of theophylline and felodipine led to an 18% reduction in theophylline area under the plasma-time concentration curve. Presumably, decreased absorption of theophylline is the cause. If theophylline and felodipine are given together, theophylline levels and patient response should be monitored and the dosage adjusted as needed. Patients should be advised to notify their physician if they experience worsening of their respiratory symptoms.

References

  1. Upton RA (1991) "Pharmacokinetic interactions between theophylline and other medication (Part II)." Clin Pharmacokinet, 20, p. 135-50
  2. Bratel T, Billing B, Dahlqvist R (1989) "Felodipine reduces the absorption of theophylline in man." Eur J Clin Pharmacol, 36, p. 481-5

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Drug and food interactions

Moderate

enalapril food

Applies to: Lexxel (enalapril / felodipine)

GENERALLY AVOID: Moderate-to-high dietary intake of potassium can cause hyperkalemia in some patients who are using angiotensin converting enzyme (ACE) inhibitors. In some cases, affected patients were using a potassium-rich salt substitute. ACE inhibitors can promote hyperkalemia through inhibition of the renin-aldosterone-angiotensin (RAA) system.

MANAGEMENT: It is recommended that patients who are taking ACE inhibitors be advised to avoid moderately high or high potassium dietary intake. Particular attention should be paid to the potassium content of salt substitutes.

References

  1. (2002) "Product Information. Vasotec (enalapril)." Merck & Co., Inc
  2. Good CB, McDermott L (1995) "Diet and serum potassium in patients on ACE inhibitors." JAMA, 274, p. 538
  3. Ray K, Dorman S, Watson R (1999) "Severe hyperkalaemia due to the concomitant use of salt substitutes and ACE inhibitors in hypertension: a potentially life threatening interaction." J Hum Hypertens, 13, p. 717-20

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Moderate

theophylline food

Applies to: Elixophyllin KI (potassium iodide / theophylline)

GENERALLY AVOID: Coadministration with caffeine may increase the serum concentrations of theophylline. The proposed mechanism involves competitive inhibition of theophylline metabolism via CYP450 1A2, as well as metabolic conversion of caffeine to theophylline in vivo and saturation of theophylline metabolism at higher serum concentrations. In six healthy male volunteers (all smokers), serum concentrations of theophylline (administered as aminophylline 400 mg single oral dose) were significantly higher following consumption of caffeine (2 to 7 cups of instant coffee over 24 hours, equivalent to approximately 120 to 630 mg of caffeine) than after caffeine deprivation for 48 hours. Caffeine consumption also increased the apparent elimination half-life of theophylline by an average of 32% and reduced its total body clearance by 23%. In another study, steady-state concentration and area under the concentration-time curve of theophylline (1200 mg intravenously over 24 hours) increased by 23% and 40%, respectively, in eight healthy volunteers following administration of caffeine (300 mg orally three times a day).

MANAGEMENT: Given the narrow therapeutic index of theophylline, patients should limit or avoid significant fluctuations in their intake of pharmacologic as well as dietary caffeine.

ADJUST DOSING INTERVAL: Administration of theophylline with continuous enteral nutrition may reduce the serum levels or the rate of absorption of theophylline. The mechanism has not been reported. In one case, theophylline levels decreased by 53% in a patient receiving continuous nasogastric tube feedings and occurred with both theophylline tablet and liquid formulations, but not with intravenous aminophylline.

MANAGEMENT: When administered to patients receiving continuous enteral nutrition , some experts recommend that the tube feeding should be interrupted for at least 1 hour before and 1 hour after the dose of theophylline is given; rapid-release formulations are preferable, and theophylline levels should be monitored.

References

  1. Jonkman JH, Sollie FA, Sauter R, Steinijans VW (1991) "The influence of caffeine on the steady-state pharmacokinetics of theophylline." Clin Pharmacol Ther, 49, p. 248-55
  2. Sato J, Nakata H, Owada E, Kikuta T, Umetsu M, Ito K (1993) "Influence of usual intake of dietary caffeine on single-dose kinetics of theophylline in healthy human subjects." Eur J Clin Pharmacol, 44, p. 295-8
  3. Wohlt PD, Zheng L, Gunderson S, Balzar SA, Johnson BD, Fish JT (2009) "Recommendations for the use of medications with continuous enteral nutrition." Am J Health Syst Pharm, 66, p. 1438-67

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Moderate

felodipine food

Applies to: Lexxel (enalapril / felodipine)

GENERALLY AVOID: The consumption of grapefruit juice may be associated with significantly increased plasma concentrations of some calcium channel blockers (CCBs) when they are administered orally. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. The interaction has been reported with the dihydropyridine CCBs (in roughly decreasing order of magnitude) felodipine, nisoldipine, nifedipine, and nimodipine, often with a high degree of interindividual variability. Grapefruit juice caused more than twofold increases in felodipine, nifedipine, and nisoldipine AUCs.

MANAGEMENT: The manufacturers of nifedipine and nisoldipine recommend avoiding grapefruit juice. Patients treated orally with other calcium channel blockers should be advised to avoid consumption of large amounts of grapefruits and grapefruit juice to prevent any undue fluctuations in serum drug levels. Increased effects on blood pressure may persist for up to 4 days after the consumption of grapefruit juice. Monitoring for calcium channel blocker adverse effects (e.g., headache, hypotension, syncope, tachycardia, edema) is recommended.

References

  1. Edgar B, Bailey D, Bergstrand R, Johnsson G, Regardh CG (1992) "Acute effects of drinking grapefruit juice on the pharmacokinetics and dynamics of felodipine--and its potential clinical relevance." Eur J Clin Pharmacol, 42, p. 313-7
  2. (2002) "Product Information. Plendil (felodipine)." Merck & Co., Inc
  3. (2002) "Product Information. Procardia (nifedipine)." Pfizer U.S. Pharmaceuticals
  4. Bailey DG, Arnold JM, Munoz C, Spence JD (1993) "Grapefruit juice--felodipine interaction: mechanism, predictability, and effect of naringin." Clin Pharmacol Ther, 53, p. 637-42
  5. Bailey DG, Arnold JMO, Spence JD (1994) "Grapefruit juice and drugs - how significant is the interaction." Clin Pharmacokinet, 26, p. 91-8
  6. Bailey DG, Arnold JM, Strong HA, Munoz C, Spence JD (1993) "Effect of grapefruit juice and naringin on nisoldipine pharmacokinetics." Clin Pharmacol Ther, 54, p. 589-94
  7. Yamreudeewong W, Henann NE, Fazio A, Lower DL, Cassidy TG (1995) "Drug-food interactions in clinical practice." J Fam Pract, 40, p. 376-84
  8. (1995) "Grapefruit juice interactions with drugs." Med Lett Drugs Ther, 37, p. 73-4
  9. (2001) "Product Information. Sular (nisoldipine)." Astra-Zeneca Pharmaceuticals
  10. Josefsson M, Zackrisson AL, Ahlner J (1996) "Effect of grapefruit juice on the pharmacokinetics of amlodipine in healthy volunteers." Eur J Clin Pharmacol, 51, p. 189-93
  11. Bailey DG, Malcolm J, Arnold O, Spence JD (1998) "Grapefruit juice-drug interactions." Br J Clin Pharmacol, 46, p. 101-10
  12. Bailey DG, Kreeft JH, Munoz C, Freeman DJ, Bend JR (1998) "Grapefruit juice felodipine interaction: Effect of naringin and 6',7'-dihydroxybergamottin in humans." Clin Pharmacol Ther, 64, p. 248-56
  13. Fuhr U, Maier-Bruggemann A, Blume H, et al. (1998) "Grapefruit juice increases oral nimodipine bioavailability." Int J Clin Pharmacol Ther, 36, p. 126-32
  14. Gunston GD, Mehta U (2000) "Potentially serious drug interactions with grapefruit juice." S Afr Med J, 90, p. 41
  15. Takanaga H, Ohnishi A, Maatsuo H, et al. (2000) "Pharmacokinetic analysis of felodipine-grapefruit juice interaction based on an irreversible enzyme inhibition model." Br J Clin Pharmacol, 49, p. 49-58
  16. Bailey DG, Dresser GR, Kreeft JH, Munoz C, Freeman DJ, Bend JR (2000) "Grapefruit-felodipine interaction: Effect of unprocessed fruit and probable active ingredients." Clin Pharmacol Ther, 68, p. 468-77
  17. Ho PC, Ghose K, Saville D, Wanwimolruk S (2000) "Effect of grapefruit juice on pharmacokinetics and pharmacodynamics of verapamil enantiomers in healthy volunteers." Eur J Clin Pharmacol, 56, p. 693-8
  18. Fuhr U, Muller-Peltzer H, Kern R, et al. (2002) "Effects of grapefruit juice and smoking on verapamil concentrations in steady state." Eur J Clin Pharmacol, 58, p. 45-53
  19. Cerner Multum, Inc. "UK Summary of Product Characteristics."
View all 19 references

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Moderate

enalapril food

Applies to: Lexxel (enalapril / felodipine)

MONITOR: Many psychotherapeutic and CNS-active agents (e.g., anxiolytics, sedatives, hypnotics, antidepressants, antipsychotics, opioids, alcohol, muscle relaxants) exhibit hypotensive effects, especially during initiation of therapy and dose escalation. Coadministration with antihypertensives and other hypotensive agents, in particular vasodilators and alpha-blockers, may result in additive effects on blood pressure and orthostasis.

MANAGEMENT: Caution and close monitoring for development of hypotension is advised during coadministration of these agents. Some authorities recommend avoiding alcohol in patients receiving vasodilating antihypertensive drugs. Patients should be advised to avoid rising abruptly from a sitting or recumbent position and to notify their physician if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia.

References

  1. Sternbach H (1991) "Fluoxetine-associated potentiation of calcium-channel blockers." J Clin Psychopharmacol, 11, p. 390-1
  2. Shook TL, Kirshenbaum JM, Hundley RF, Shorey JM, Lamas GA (1984) "Ethanol intoxication complicating intravenous nitroglycerin therapy." Ann Intern Med, 101, p. 498-9
  3. Feder R (1991) "Bradycardia and syncope induced by fluoxetine." J Clin Psychiatry, 52, p. 139
  4. Ellison JM, Milofsky JE, Ely E (1990) "Fluoxetine-induced bradycardia and syncope in two patients." J Clin Psychiatry, 51, p. 385-6
  5. Rodriguez de la Torre B, Dreher J, Malevany I, et al. (2001) "Serum levels and cardiovascular effects of tricyclic antidepressants and selective serotonin reuptake inhibitors in depressed patients." Ther Drug Monit, 23, p. 435-40
  6. Cerner Multum, Inc. "Australian Product Information."
  7. Pacher P, Kecskemeti V (2004) "Cardiovascular side effects of new antidepressants and antipsychotics: new drugs, old concerns?" Curr Pharm Des, 10, p. 2463-75
  8. Andrews C, Pinner G (1998) "Postural hypotension induced by paroxetine." BMJ, 316, p. 595
View all 8 references

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Moderate

felodipine food

Applies to: Lexxel (enalapril / felodipine)

MONITOR: Many psychotherapeutic and CNS-active agents (e.g., anxiolytics, sedatives, hypnotics, antidepressants, antipsychotics, opioids, alcohol, muscle relaxants) exhibit hypotensive effects, especially during initiation of therapy and dose escalation. Coadministration with antihypertensives and other hypotensive agents, in particular vasodilators and alpha-blockers, may result in additive effects on blood pressure and orthostasis.

MANAGEMENT: Caution and close monitoring for development of hypotension is advised during coadministration of these agents. Some authorities recommend avoiding alcohol in patients receiving vasodilating antihypertensive drugs. Patients should be advised to avoid rising abruptly from a sitting or recumbent position and to notify their physician if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia.

References

  1. Sternbach H (1991) "Fluoxetine-associated potentiation of calcium-channel blockers." J Clin Psychopharmacol, 11, p. 390-1
  2. Shook TL, Kirshenbaum JM, Hundley RF, Shorey JM, Lamas GA (1984) "Ethanol intoxication complicating intravenous nitroglycerin therapy." Ann Intern Med, 101, p. 498-9
  3. Feder R (1991) "Bradycardia and syncope induced by fluoxetine." J Clin Psychiatry, 52, p. 139
  4. Ellison JM, Milofsky JE, Ely E (1990) "Fluoxetine-induced bradycardia and syncope in two patients." J Clin Psychiatry, 51, p. 385-6
  5. Rodriguez de la Torre B, Dreher J, Malevany I, et al. (2001) "Serum levels and cardiovascular effects of tricyclic antidepressants and selective serotonin reuptake inhibitors in depressed patients." Ther Drug Monit, 23, p. 435-40
  6. Cerner Multum, Inc. "Australian Product Information."
  7. Pacher P, Kecskemeti V (2004) "Cardiovascular side effects of new antidepressants and antipsychotics: new drugs, old concerns?" Curr Pharm Des, 10, p. 2463-75
  8. Andrews C, Pinner G (1998) "Postural hypotension induced by paroxetine." BMJ, 316, p. 595
View all 8 references

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Moderate

felodipine food

Applies to: Lexxel (enalapril / felodipine)

MONITOR: Calcium-containing products may decrease the effectiveness of calcium channel blockers by saturating calcium channels with calcium. Calcium chloride has been used to manage acute severe verapamil toxicity.

MANAGEMENT: Management consists of monitoring the effectiveness of calcium channel blocker therapy during coadministration with calcium products.

References

  1. Henry M, Kay MM, Viccellio P (1985) "Cardiogenic shock associated with calcium-channel and beta blockers: reversal with intravenous calcium chloride." Am J Emerg Med, 3, p. 334-6
  2. Moller IW (1987) "Cardiac arrest following intravenous verapamil combined with halothane anaesthesia." Br J Anaesth, 59, p. 522-6
  3. Oszko MA, Klutman NE (1987) "Use of calcium salts during cardiopulmonary resuscitation for reversing verapamil-associated hypotension." Clin Pharm, 6, p. 448-9
  4. Schoen MD, Parker RB, Hoon TJ, et al. (1991) "Evaluation of the pharmacokinetics and electrocardiographic effects of intravenous verapamil with intravenous calcium chloride pretreatment in normal subjects." Am J Cardiol, 67, p. 300-4
  5. O'Quinn SV, Wohns DH, Clarke S, Koch G, Patterson JH, Adams KF (1990) "Influence of calcium on the hemodynamic and anti-ischemic effects of nifedipine observed during treadmill exercise testing." Pharmacotherapy, 10, p. 247
  6. Woie L, Storstein L (1981) "Successful treatment of suicidal verapamil poisoning with calcium gluconate." Eur Heart J, 2, p. 239-42
  7. Morris DL, Goldschlager N (1983) "Calcium infusion for reversal of adverse effects of intravenous verapamil." JAMA, 249, p. 3212-3
  8. Guadagnino V, Greengart A, Hollander G, Solar M, Shani J, Lichstein E (1987) "Treatment of severe left ventricular dysfunction with calcium chloride in patients receiving verapamil." J Clin Pharmacol, 27, p. 407-9
  9. Luscher TF, Noll G, Sturmer T, Huser B, Wenk M (1994) "Calcium gluconate in severe verapamil intoxication." N Engl J Med, 330, p. 718-20
  10. Bar-Or D, Gasiel Y (1981) "Calcium and calciferol antagonise effect of verapamil in atrial fibrillation." Br Med J (Clin Res Ed), 282, p. 1585-6
  11. Lipman J, Jardine I, Roos C, Dreosti L (1982) "Intravenous calcium chloride as an antidote to verapamil-induced hypotension." Intensive Care Med, 8, p. 55-7
  12. McMillan R (1988) "Management of acute severe verapamil intoxication." J Emerg Med, 6, p. 193-6
  13. Perkins CM (1978) "Serious verapamil poisoning: treatment with intravenous calcium gluconate." Br Med J, 2, p. 1127
  14. Moroni F, Mannaioni PF, Dolara A, Ciaccheri M (1980) "Calcium gluconate and hypertonic sodium chloride in a case of massive verapamil poisoning." Clin Toxicol, 17, p. 395-400
View all 14 references

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Moderate

theophylline food

Applies to: Elixophyllin KI (potassium iodide / theophylline)

GENERALLY AVOID: Coadministration with caffeine may increase the serum concentrations of theophylline. The proposed mechanism involves competitive inhibition of theophylline metabolism via CYP450 1A2, as well as metabolic conversion of caffeine to theophylline in vivo and saturation of theophylline metabolism at higher serum concentrations. In six healthy male volunteers (all smokers), serum concentrations of theophylline (administered as aminophylline 400 mg single oral dose) were significantly higher following consumption of caffeine (2 to 7 cups of instant coffee over 24 hours, equivalent to approximately 120 to 630 mg of caffeine) than after caffeine deprivation for 48 hours. Caffeine consumption also increased the apparent elimination half-life of theophylline by an average of 32% and reduced its total body clearance by 23%. In another study, steady-state concentration and area under the concentration-time curve of theophylline (1200 mg intravenously over 24 hours) increased by 23% and 40%, respectively, in eight healthy volunteers following administration of caffeine (300 mg orally three times a day).

MANAGEMENT: Given the narrow therapeutic index of theophylline, patients should limit or avoid significant fluctuations in their intake of pharmacologic as well as dietary caffeine.

References

  1. Jonkman JH, Sollie FA, Sauter R, Steinijans VW (1991) "The influence of caffeine on the steady-state pharmacokinetics of theophylline." Clin Pharmacol Ther, 49, p. 248-55
  2. Sato J, Nakata H, Owada E, Kikuta T, Umetsu M, Ito K (1993) "Influence of usual intake of dietary caffeine on single-dose kinetics of theophylline in healthy human subjects." Eur J Clin Pharmacol, 44, p. 295-8

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Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

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