Drug interaction

interactdrug interactionsdrug-drug interactioninteractiondrug-drug interactionsinteractionsinteractsadditiveDrug-interactionDrug–drug interaction
A drug interaction is a situation in which a substance (usually another drug) affects the activity of a drug when both are administered together.wikipedia
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Herb-drug interactions

However, interactions may also exist between drugs and foods (drug-food interactions), as well as drugs and medicinal plants or herbs (herb-drug interactions).
Herb-drug interactions are drug interactions that occur between herbal medicines and conventional drugs.

Drug overdose

overdoseoverdosingoverdosed
If a patient is taking two drugs and one of them increases the effect of the other it is possible that an overdose may occur.
The term 'overdose' is often misused as a descriptor for adverse drug reactions or negative drug interactions due to mixing multiple drugs simultaneously.

Antibiotic

antibioticsantibacterialantibacterials
Or the combination of clavulanic acid with amoxicillin in order to overcome bacterial resistance to the antibiotic.
Additional side-effects can result from interaction with other drugs, such as the possibility of tendon damage from the administration of a quinolone antibiotic with a systemic corticosteroid.

Polypharmacy

pill burdenmultiple chronic diseasesmixing multiple drugs simultaneously
Polypharmacy: The more drugs a patient takes the more likely it will be that some of them will interact.
Concerns about polypharmacy include increased adverse drug reactions, drug interactions, prescribing cascade, and higher costs.

Cimetidine

Tagamet
Such as occurs when cimetidine is taken with didanosine.
Due to its non-selective inhibition of cytochrome P450 enzymes, cimetidine has numerous drug interactions.

Drug metabolism

metabolismxenobiotic metabolismmetabolic stability
Many drug interactions are due to alterations in drug metabolism.
Drug metabolism also affects multidrug resistance in infectious diseases and in chemotherapy for cancer, and the actions of some drugs as substrates or inhibitors of enzymes involved in xenobiotic metabolism are a common reason for hazardous drug interactions.

CYP2D6

2D6cytochrome p-450 cyp2d6cytochrome P450 2D6
Of the various families that are present in human beings the most interesting in this respect are the 1, 2 and 3, and the most important enzymes are CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4.
If such a drug is taken at the same time as a second drug that is a CYP2D6 substrate, the first drug may affect the elimination rate of the second through what is known as a drug-drug interaction.

Enzyme

enzymologyenzymesenzymatic
Genetic factors: Genes synthesize enzymes that metabolize drugs. Some races have genotypic variations that could decrease or increase the activity of these enzymes. The consequence of this would, on occasions, be a greater predisposition towards drug interactions and therefore a greater predisposition for adverse effects to occur. This is seen in genotype variations in the isozymes of cytochrome P450.
Induction or inhibition of these enzymes can cause drug interactions.

Pharmacokinetics

pharmacokineticsteady-statesteady state
These processes may include alterations in the pharmacokinetics of the drug, such as alterations in the absorption, distribution, metabolism, and excretion (ADME) of a drug.

Cytochrome P450

cytochrome P-450cytochrome P450 oxidaseCYP
Genetic factors: Genes synthesize enzymes that metabolize drugs. Some races have genotypic variations that could decrease or increase the activity of these enzymes. The consequence of this would, on occasions, be a greater predisposition towards drug interactions and therefore a greater predisposition for adverse effects to occur. This is seen in genotype variations in the isozymes of cytochrome P450.
This is a major source of adverse drug interactions, since changes in CYP enzyme activity may affect the metabolism and clearance of various drugs.

Grapefruit

grapefruitspink grapefruitwhite grapefruit
Acting on the P-glycoprotein of the enterocytes: This appears to be one of the mechanisms promoted by the consumption of grapefruit juice in increasing the bioavailability of various drugs, regardless of its demonstrated inhibitory activity on first pass metabolism.
Grapefruit and grapefruit juice have been found to interact with numerous drugs and in many cases, to result in adverse direct and/or side effects (if dosage is not carefully adjusted.)

Warfarin

coumadincoumarinrat poison
Finally, another possibility is that the drug is retained in the intestinal lumen forming large complexes that impede its absorption. This can occur with cholestyramine if it is associated with sulfamethoxazol, thyroxine, warfarin or digoxin.
Warfarin interacts with many commonly used drugs, and the metabolism of warfarin varies greatly between patients.

Monoamine oxidase inhibitor

monoamine oxidase inhibitorsMAOIMAOIs
People taking antidepressant drugs such as monoamine oxidase inhibitors should not take food containing tyramine as hypertensive crisis may occur (an example of a drug-food interaction).
The most significant risk associated with the use of MAOIs is the potential for drug interactions with over-the-counter and prescription medicines, ‘controlled’ drugs or medications, and some dietary supplements (e.g., St. John's wort, tryptophan).

Pharmacist

pharmacistsdruggistchemist
Drug interactions can be checked for free online with interaction checkers (note that not all drug interaction checkers provide the same results, and only a drug information expert, such as a pharmacist, should interpret results or provide advice on managing drug interactions)
Pharmacists undergo university-level education to understand the biochemical mechanisms and actions of drugs, drug uses, therapeutic roles, side effects, potential drug interactions, and monitoring parameters.

Carbamazepine

Tegretolcarbazepine
Carbamazepine has a potential for drug interactions; caution should be used in combining other medicines with it, including other antiepileptics and mood stabilizers.

Aspirin

acetylsalicylic acidASAbaby aspirin
Aspirin is known to interact with other drugs.

Benzodiazepine

benzodiazepinesbenzodiazapines1,4-benzodiazepine
Individual benzodiazepines may have different interactions with certain drugs.

Amphetamine

speedbenzedrineamphetamines
Many types of substances are known to interact with amphetamine, resulting in altered drug action or metabolism of amphetamine, the interacting substance, or both.

Ginger

ginger rootZingiberis Rhizomagingers
It is on the FDA's "generally recognized as safe" list, though it does interact with some medications, including the anticoagulant drug warfarin and the cardiovascular drug nifedipine.

Medication

pharmaceuticalpharmaceuticalsdrug
A drug interaction is a situation in which a substance (usually another drug) affects the activity of a drug when both are administered together.

Synergy

synergisticsynergiessynergistically
This action can be synergistic (when the drug's effect is increased) or antagonistic (when the drug's effect is decreased) or a new effect can be produced that neither produces on its own.

Antagonism (chemistry)

antagonisticantagonismAntagonistic interaction
This action can be synergistic (when the drug's effect is increased) or antagonistic (when the drug's effect is decreased) or a new effect can be produced that neither produces on its own.

Medicinal plants

medicinal plantmedicinal herbmedicinal herbs
However, interactions may also exist between drugs and foods (drug-food interactions), as well as drugs and medicinal plants or herbs (herb-drug interactions).

Herb

herbsculinary herbculinary
However, interactions may also exist between drugs and foods (drug-food interactions), as well as drugs and medicinal plants or herbs (herb-drug interactions).