Table 2.

Commonly encountered drug-food interactions and recommendations (outside Ramadan)

Drug	Interaction	Recommendation
Levothyroxine	Intake with food may decrease absorption.w13 High fibre diets have been shown to decrease levothyroxine absorption.w14 Levothyroxine absorption is increased when it is taken on an empty stomachw15	Thyroid hormones should be taken an hour before eating, at the same time every dayw14
Digoxin	High fibre foods, such as whole wheat products, raw vegetables, bran cereal, and fruits, inhibit absorption of digoxin and decrease its effectw16	To avoid this problem, patients should take digoxin one hour before food or two hours after eatingw17
Verapamil/felodipine	Ingestion of grapefruit juice has been shown to increase absorption of verapamilw17 and felodipinew18	In order to prevent side effects of these drugs, patients who are taking verapamil or felodipine, or similar drugs such as amlodipine and nifedipine, should avoid grapefruit and its juicew17 w18
Propranolol	High protein foods may interfere with propranolol metabolism by increasing blood concentrations and activity of propranololw19
Lithium	Foods that alkalinise the urine may increase elimination of lithium from the body, potentially decreasing its actionsw17
Theophylline	A diet low in carbohydrates and high in protein, as well as charcoal grilled beef, increases elimination of theophylline, resulting in poor control of asthma and other conditions. Therefore, a high carbohydrate, low protein diet will halt elimination of theophylline, leading to optimal therapeutic effectw20	Food can have different effects depending on the dose form. Sustained release forms of theophylline should be taken on an empty stomach. Liquid and non-sustained release theophylline products are best taken on an empty stomach, but they may be taken with food if stomach upset occursw20
Loratadine	Food slows the absorption of loratadine and also increases the total amount absorbedw21	Loratadine should be taken on an empty stomachw21
Fexofenadine	Ingestion of grapefruit juice, orange juice, or apple juice along with fexofenadine decreases its blood concentrationsw22
Carbamazepine	Grapefruit juice increases the bioavailability of carbamazepine by inhibiting CYP3A4 enzymes in gut wall and liverw23
Diazepam	Substantial increase of absorption with grapefruit juicew24
Bisphosphonates	Food substantially reduces the bioavailability of oral alendronate.w25 Taking alendronate either 60 or 30 minutes before a standardised breakfast reduced bioavailability by 40% relative to a two hour wait. Black coffee or orange juice alone, when taken with the drug, also reduced bioavailability (approximately 60%)w26	A practical dosing recommendation is that patients should take the drugs with water after an overnight fast and at least 30 minutes before any other food or beverage