Table

Drug interactions of some commonly used drugs in dermatology

M. J. Cyriac Department of Dermatology and Venereology, Medical College, Kottayam, India.

Address for correspondence: Dr. M. J. Cyriac, Professor and Head, Department of Dermatology and Venereology, Medical College, Kottayam, India. E-mail: [email protected]

Drug interactions leading to serious adverse effects are alternative medicines or food should also be borne in to be cautiously watched for when multiple drugs are mind.2 Increased risk of drug induced toxicity or used simultaneously.1 It is important for the physician therapeutic failure can occur when a new drug is added to be aware of these interactions. Although in many to a treatment regimen. It is impossible to remember instances the adverse interaction does not reach a all possible drug interactions. A ready to refer checklist magnitude of recognizable clinical expression, rarely is useful as a handy reference. it can result in a serious adverse outcome. Some of the commonly used drugs in dermatology and Adverse drug interactions may lead to increased their interactions, resultant clinical effect and possible toxicity, decreased efficacy or both. The possibility of underlying mechanisms are given in Table 1. Table 2 lists interaction with non-prescription drugs, herbal or the drugs with their relative risk for inducing interactions.

Table 1: Drug interactions of some commonly used drugs Drug Interacting drug Adverse effect Remarks

Erythromycin/Clarithromycin Theophylline Theophylline toxicity Precipitates seizures Carbamazepine CNS depression Digoxin Digoxin toxicity Triazolam CNS depression Ergotamine Ergotism Warfarin Bleeding Cyclosporine/Tacrolimus Nephrotoxicity Statins Rhabdomyolysis Astemizole/Terfenadine Cardiac arrhythmias Cisapride Cardiac arrhythmias Pimozide Cardiac arrhythmias Sodium valproate Valproate toxicity

Fluoroquinolones Theophylline Theophylline toxicity Antacid/sucralfate Decreased antibiotic levels

Tetracycline Antacid/sucralfate Decreased antibiotic levels

Trimethoprim- Phenytoin Phenytoin toxicity sulfamethoxazole Oral hypoglycemics Hypoglycemia Digoxin Digoxin toxicity Warfarin Bleeding

How to cite this article: Cyriac MJ. Drug interactions of some commonly used drugs in dermatology. Indian J Dermatol Venereol Leprol 2004;70:54-6. Received: November, 2003. Accepted: January, 2004. Source of Support: Nil.

Indian J Dermatol Venereol Leprol January-February 2004 Vol 70 Issue 1 54 Cyriac MJ: Drug interactions of some commonly used drugs in dermatology

Table 1: Drug interactions of some commonly used drugs (contd.) Drug Interacting drug Adverse effect Remarks Metronidazole Ethanol Disulfiram-like reactions Fluorouracil Bone marrow suppression Warfarin Bleeding

Rifampicin3 Oral contraceptives Failure – pregnancy Start on alternative methods of contraception Warfarin Clot formation Cyclosporine/tacrolimus Transplant rejection Double or triple steroid dose Corticosteroids Loss of steroid effect Phenytoin Loss of seizure control HIV-1 protease inhibiters Increased viral load, Resistance Itraconazole Decreased drug levels Ketoconazole Decreased drug levels Statins Hypercholesterolemia Diltiazem/Verapamil Reduced drug levels Digoxin Decreased digoxin levels Watch for arrhythmia

Methotrexate 4 Frusemide Acute toxicity Due to decreased renal NSAIDs elimination Penicillins Probenecid NSAIDs Acute toxicity Due to displacement Salicylates from plasma protein Sulfonamides binding

Isotretinoin/Acitretin Tetracycline Pseudotumor cerebri Synergistic effect Alcohol

H1 antihistamines: Terfenadine Ketoconazole/Itraconazole Increased levels QT prolongation, and astemizole Fluconazole torsaides de-pointes

Azole antifungals: Ketoconazole, Antacids/H2 blockers Decreased therapeutic effect Reduces absorption itraconazole and fluconazole Omeprazole Phenytoin Increased levels Due to CYP3A4 inhibition Warfarin Bleeding Cyclosporin Increased levels Cisapride Increased levels Fatal QT prolongation Triazolam/Midazolam Increased levels Statins Rhabdomyolysis Excessive sedation

Itraconazole Nifedipine Increased levels Leg edema

Table 2: Relative safety within drug categories for inducing interactions Drug class Greater potential for interaction Less potential for interaction Macrolides Erythromycin Azithromycin Clarithromycin

H1 antihistamines Astemizole Loratidine Terfenadine Cetirizine Fexofenadine

H2 antihistamines Cimetidine Famotidine Ranitidine

Fluoroquinolones Ciprofloxacin Levofloxacin Enoxacin Ofloxacin

Statins Simvastatin Pravastatin Lovastatin Fluvastatin Atorvastatin Cerivastatin

55 Indian J Dermatol Venereol Leprol January-February 2004 Vol 70 Issue 1 Cyriac MJ: Drug interactions of some commonly used drugs in dermatology

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