Drug Drug Interaction and Drug Food Interaction
Document4 pagesB.Pharm, Pharm.D
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Overview of Drug-Drug Interaction and Drug Food Interaction.
- drug interactions
- food-drug interactions
- pharmacokinetics
- adverse effects
- medication safety
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- Page 1. Type of Interaction Object / Affected Drug Pricipitant / Interacting Drug Effect / Influence on Object Drug Complexation & Adsorption Cephrofloxacine, Penicillamine Antacids, Food & Mineral supplements containing Al, Mg, Fe, Zn, Ca ions Formation of poorly soluble and unabsorbable complex with heavy metal ions. Sulphonamides, Aspirin, Ferrous sulphate Antacids Enhanced dissolution and absorption rate. Sulphonamides, Aspirin, Ferrous sulphate Sodium bicarbonate, Calcium carbonate Decreased dissolution and hence absorption. Aspirin, Diazepam, Levodopa, Mexiletine Metoclopramide Rapid gastric emptying; increased rate of absorption. Levodopa, Lithium carbonate, Mexiletine Anticholinergics Delayed gastric emptying; decreased rate of absorption. Alteration of GI Microflora Digoxin Antibiotics Increased bioavailability due to destruction of bacterial flora that inactivates digoxin in lower intestine. Malabsorption Syndrome Vitamin A, B12, Digoxin Neomycin Inhibition of absorption due to malabsorption. Anticoagulants Phenylbutazone, Chloral hydrate Increased clotting time; increased risk of hemorrhage. Tolbutamide Sulphonamides Increased hypoglycemic effect. Drug Drug Interactions ABSORPTION INTERACTIONS COMPETITIVE DISPLACEMENT INTERACTIONS METABOLISM INTERACTIONS Alteration of GI pH Alteration of Gut Motility
- Page 2. Corticosteroids, Oral contraceptives, Coumarins, Phenytoin Barbiturates Decreased plasma levels; decreased efficacy of object drugs. Oral contraceptives, Oral hypoglycaemics Rifampicin Decreased plasma levels. Tyramine-rich food MAO inhibitors Enhanced absorption of unmetabolised tyramine. Coumarins Metronidazole, Phenylbutazone Increased anticoagulant activity. Alcohol Disulfiram, Metronidazole Increased plasma acetaldehyde levels. Changes in Active Tubular Secretion Penicillin, Cephalosporins, Nalidixic acid Probenecid Elevated plasma levels of acidic drugs. Changes in Urine pH Amphetamine Antacids, Thiazides, Acetazolamide Increased passive reabsorption of basic drugs; increased risk of toxicity. Changes in Renal Blood Flow Lithium bicarbonate NSAIDs Decreased renal clearance of lithium; risk of toxicity. CNS depressants (e.g., alcohol, benzodiazepines, opioids) Other sedatives, antihistamines Enhanced CNS depression, increased sedation and respiratory suppression. Antihypertensives Diuretics or other antihypertensives Excessive fall in blood pressure, postural hypotension. Sulfonamides Trimethoprim Potentiation of antibacterial effect (synergistic therapy). Levodopa Carbidopa Potentiation of dopaminergic activity, enhanced antiparkinsonian effect. PHARMACODYNAMIC DRUG–DRUG INTERACTIONS Additive Effect Synergistic Effect EXCRETION INTERACTIONS 1. Enzyme Induction 2. Enzyme Inhibition
- Page 3. NSAIDs Antihypertensive drugs (ACE inhibitors, β-blockers) Reduced antihypertensive efficacy. Levodopa Antipsychotics (e.g., chlorpromazine, haloperidol) Reduced antiparkinsonian effect due to dopamine receptor blockade. Insulin or Oral hypoglycemics Corticosteroids Hyperglycemia; antagonism of hypoglycemic effect. Warfarin Vitamin K or estrogens Decreased anticoagulant effect; increased clotting risk. β-blockers β-agonist bronchodilators Functional antagonism; reduced bronchodilator response. Tetracyclines, Fluoroquinolones Milk and dairy products (Ca²⁺-rich food) Formation of insoluble chelates; decreased drug absorption. Iron supplements Tea, coffee Tannins inhibit iron absorption. Digoxin High-fiber foods, bran Decreased absorption due to binding with fiber. Statins (Simvastatin, Atorvastatin) Grapefruit juice Inhibition of CYP3A4; increased plasma concentration and toxicity risk. Theophylline High-carbohydrate diet Altered metabolism; variable plasma levels. Warfarin Foods rich in vitamin K (spinach, cabbage, broccoli) Decreased anticoagulant effect. MAO inhibitors Tyramine-rich foods (cheese, red wine, bananas) Hypertensive crisis due to accumulation of norepinephrine. Alcohol Metronidazole, Disulfiram Disulfiram-like reaction—flushing, nausea, vomiting. Alteration of Absorption Metabolic Interactions Pharmacologic / Physiologic Effect DRUG–FOOD INTERACTIONS Antagonistic Effect Opposing Pharmacologic Actions
- Page 4. β-blockers Asthma, COPD Bronchoconstriction; worsening of respiratory symptoms. Metformin Renal impairment Lactic acidosis risk due to reduced clearance. Corticosteroids Diabetes mellitus Exacerbation of hyperglycemia, impaired glucose control. NSAIDs Peptic ulcer disease Increased risk of gastric irritation, bleeding, or ulcer perforation. Sedatives, Opioids Sleep apnea, COPD Enhanced respiratory depression. Estrogens, Oral contraceptives Liver disease Impaired metabolism, increased toxicity risk. ACE inhibitors, Potassium- sparing diuretics Renal failure Severe hyperkalemia, arrhythmia risk. DRUG–DISEASE INTERACTIONS
