Does it matter?
In short, yes, it can matter. How? That depends.
In general, the effect of food primarily concerns medicines for oral administration when the drug is taken shortly before or after a meal as it alters the absorption of the drug from the guts. These interactions may be managed or mitigated by carefully planning the time of the taking drug and the meal.
Some drugs are not compatible with certain food due to their mechanism of actions in the body. These interactions occur when the drug and the food interfere with each other in the body. In such situations, patients are advised to limit or avoid those foods in their diet throughout the course of their treatment, and in some cases, for a certain period before and after the treatment.
Pharmacokinetics & Pharmacodynamics
To have a better appreciation of this topic, it is worth introducing some basic concepts of pharmacokinetics (PK) and pharmacodynamics (PD).
PK describes what the body does to the drug, including absorption, distribution, metabolism and excretion (ADME). It concerns the amount of drug absorbed into the body and how long it resides there. A drug needs to reach an effective level at the site of action for its effect.
PD describes what the drug does to the body. It concerns the mechanism of action and the resulting effect of the drug. For instance, antidepressants and opioid pain killers act on receptors in the central nervous system for their effect.
Drug interactions can be PK or PD in nature and their mitigation strategies are correspondingly different.
Food effect on drug absorption
The effect of food on drug absorption is a PK interaction. These interactions can either be local resulting from the concurrent digestion of food in the guts or systemic due to the change in absorptive capacity caused by the food in the body. It should be noted that food can either decrease or increase the absorption of drug.
In general, meals delay the passage of content from the stomach to the small intestine and lead to slower absorption. The increased acid secretion in the stomach can breakdown some drugs that are not stable in acidic environment. These interactions may be managed or mitigated by carefully planning the time of the taking drug and the meal. For example, ampicillin, a penicillin antibiotic, is known to be absorbed poorly with food. Food increases both the release of stomach acid and the residence time of the drug in the stomach leading to increased chemical degradation of the drug. Patients are advised to take them on an empty stomach at least 30 min before meals for maximum absorption and effect. For some poorly water soluble drugs, the release of bile during digestion can help dissolving the drug in the guts and facilitate absorption. Patients are advised to take these medicines with meals for therapeutic effects.
While the impact on absorption may be managed by taking the drug and the food at different times for some drugs, this is not always the case. For instance, grapefruit juice is known to inhibit a family of metabolising enzymes that breakdown some drugs during absorption from the gut and hence increases the amount of drug absorbed. This can lead to an unintentional and inconsistent increase in drug absorption and excessive effects. Since the effect is long-lasting, simply separating the dose of medicine and the ingestion of grapefruit juice does not prevent the interaction. Patients are advised to completely avoid grapefruit juice during the course of treatment with these medicines.
Food effect on drug action
Some foods interact with the drug due to the drug’s mechanisms of action in the body. These interactions are PD interactions and can occur even for medicines not taken via the guts.
For example, warfarin, an anticoagulant, works by decreasing the amount of vitamin K in your body. If there is a big change in the amount of vitamin K in your diet, the effect of warfarin could be affected. The same dose of warfarin could be less effective due to the increased amount of vitamin K. Conversely, the risk of side effect such as unwanted bleeding could be increased due to the reduced amount of vitamin K. Therefore, the key is to avoid big changes of vitamin K in your diet so to maintain and consistent level.
MAOI, or monoamine oxidase inhibitor, is a type of antidepressant. It works by inhibiting the enzyme known as monoamine oxidase to balance the level of signalling chemicals in the brains. The same enzyme is also responsible for breaking down tyramine, a amino acid that helps regulate blood pressure. Foods and drinks containing a high level of tyramine can cause dangerous reactions if they are taken with an MAOI.
These interactions cannot be avoided by taking the food and the medicine and different times. Patients are advised to be cautious about their dietary options throughout the course of treatment to ensure the medicine is safe and effective for their conditions.
Food to help the use of medicine
Fitting dosing regimens with the patient’s daily routine can improve adherence to the therapy, commonly by matching the times of the doses with mealtimes. This leads to the general advice of taking medicines at consistent with meals. For some medicines, food can help to reduce the risk of side effects in the guts. Certain medicines for diabetes work by reducing the blood sugar level after meals. To avoid excessively low blood sugar level, these medicines should be skipped if a meal is skipped.
Be cautious and informed
The interaction between food and drug is complex and drug specific. It is not the intention of this post to provide an exhaustive list of food-drug interactions. Rather, it aims to introduce to the readers why food and drug interaction can be important. If in doubt, consult your local pharmacist before using any new medicine.
CAREX 
Leave a comment