The presence of food alters the extent or rate of absorption. Therefore, the effect of food-drug interaction is crucial for clinical decision making. In this article, Dr Jyotirmoy Pal elaborates on 13 antimicrobial drug & food interactions that doctors, as well as patients, should be aware of. This article is adapted from another article taken from the journal Exploratory Animal And Medical Research.

In the published article, it has been discussed well by the authors. If we summarise the message given in the article, we would find the following information:

1. Pharmacokinetics- The principles of the body’s action to drugs is extremely important to understand the rationale of prescribing drugs at right time in relation to food timing.
2. Pharmacokinetic characteristics of drugs are absorption, distribution, metabolism and elimination.
3. We need to understand the concept of absorption and bioavailability.
   1. Absorption is defined as the movement of drugs from their site of administration to a compartment where it needs to present to produce the desired action.
   2. Bioavailability is defined as the fraction of a drug that reaches its site of action or a biological fluid from which the drug has access to the site of action.
4. Food interferes with the absorption and the bioavailability of drugs. Antimicrobial drugs are important in these instances as we need to emphasise their effectiveness by maximising absorption.
5. While prescribing antibiotics, dosage timing and the relationship with food is important to achieve maximum bioavailability. The authors of the paper mentioned above had described the need to achieve maximum bioavailability and ingesting drugs on an empty stomach before a meal would maximise the absorption.
6. These could increase gastrointestinal adverse effects as well. They stress on balanced decision making.
7. It is also important to know food-antimicrobial drug adverse interactions which may raise safety concerns in patients.

Food+drug reactions

Some of the antimicrobial drugs that were discussed in that article with respect to food and drug reaction are as follows:

1. Sulphonamides- They are absorbed rapidly from the gastrointestinal tract, except locally acting ones. They can be found in urine within thirty minutes of oral intake. This group of drugs does not cause a food-drug reaction but there is a chance of crystalluria which can be prevented by adequate hydration. The two most common antimicrobial drugs of this category are sulphamethoxazole and sulphadiazine.
2. Trimethoprim- This group of drugs increases the serum potassium level in patients with high dose intake. Special caution should be taken for patients with renal failure, concomitant hyperkalemic drug users and patients with hyperkalemia. Patients who are on a high dosage of trimethoprim should avoid potassium-rich food.
3. Fluoroquinolones- Food does not impair the oral absorption of fluoroquinolone but may delay the time to peak serum concentration. The drugs present in this category include ciprofloxacin, moxifloxacin and levofloxacin which can be taken before or after food intake. Levofloxacin oral solution can be taken one hour before food intake or two hours after the food intake. Oral absorption of fluoroquinolones is decreased by the presence of divalent and trivalent cations. Aluminium, calcium and magnesium decrease the bioavailability of fluoroquinolones. In heavy coffee users, fluoroquinolones increase the concentration of caffeine in the blood and enhancement of stimulus of the CNS. Hence, caffeine-containing drinks should be avoided by patients who are on fluoroquinolone. Caution should be provided while administering this drug to professional athletes.
4. Nitrofurantoin- This is the most rapid and almost completely absorbed drug from the GI tract that has no significant drug-food interaction and it is advised to take this drug after a meal. However, a urine alkaliniser reduces the antimicrobial effect of the drug and therefore all alkali mixtures should be avoided for better results.
5. Penicillin V and other oral Penicillins- The absorption of all penicillin is hampered by the presence of food. Except for amoxicillin, all penicillin can be administered one to two hours prior or two to four hours after intake of food.
6. Cephalosporin- There is no significant drug-food interaction with this type of drug however cefaclor concentration decreases if taken with food.
7. Tetracycline- The drug absorption after oral administration of this category of drug is above 60 to 80%. The best outcome exerted by the drug is if it is taken on an empty stomach, one hour before a meal and two hours after a meal with one full glass of water. To prevent gastrointestinal effects, the drug should be administered after intake of a meal. The presence of divalent and trivalent cations like calcium, magnesium, iron and aluminium impairs the effects of absorption of the drug by chelating and insoluble compound formation.
8. Macrolide- The absorption of erythromycin is higher on an empty stomach rather than with food. In gastrointestinal upsets, low-fat meals or snacks can be administered with it. Grapefruit juice increases the bioavailability and concomitant use of erythromycin and grapefruit juice causes adverse drug-drug interaction with other drugs. Azithromycin can be administered one hour before intake of food or two hours after a meal. The presence of bivalent and trivalent cation decreases the peak serum drug concentration but not its overall bioavailability.
9. Clindamycin- It is absorbed well and does not interact with food and can be administered irrespective of food timing.
10. Linezolid- It is completely absorbed orally. A patient who is on linezolid should avoid taking tyramine containing food which includes cheese, yoghurt, beef or chicken liver etc. Alcohol and an excessive amount of chocolates should be avoided.
11. Anti-tubercular drugs- Ethambutol can be taken before or after food intake. Isoniazid, rifampicin and pyrazinamide should be taken on an empty stomach with a full glass of water. The patient who is on this drug should avoid tyramine rich food as it causes serotonin syndrome. Alcohol should be prevented as it may cause isoniazid-related hepatotoxicity. Histamine-rich food should also be avoided for this category.
12. Antiprotozoal drug- Metronidazole produces a disulfiram-like reaction if alcohol is consumed within three days of drug therapy. Metronidazole causes a metallic taste and does not impair its bioavailability and should be administered after a meal.
13. Antifungal drug- Litraconazole should be administered after a full meal, posaconazole should be taken with a meal, within twenty minutes of the meal or with a liquid nutritional supplement. Voriconazole should be taken on an empty stomach but griseofulvin should be taken with fatty foods.

Reference: Samajdar SS, Mukherjee S, Tripathi SK (2021) on Antimicrobial drug administration and food timings: Clinico-pharmacological considerations published in Explor Anim Med Res 11(1): 10-13. DOI: 10.52635/EAMR/11.110-13

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

The author is a Professor of Medicine from Kolkata and has a WHO fellowship in Geriatric Medicine.