Medication Interactions

Medication Interactions

• When patients take multiple medications (prescription or OTC), a potential for medication interaction exists.

Types of Medication Interactions

• Weakening or Potentiating Effects: One medication can either weaken or strengthen the effects of another.

• Altering Adverse Effects: One medication can worsen or lessen the adverse effects of another.

• Increased Blood Levels and Toxicity: One medication can increase the levels of another in the bloodstream, potentially leading to toxicity.

Examples of Drug-Drug Interactions

• Levothyroxine and Supplements:

  • Taking levothyroxine (for thyroid issues) with iron or calcium supplements can reduce the absorption of levothyroxine.

• Cimetidine and Metformin:

  • Taking cimetidine (for stomach ulcers) with metformin (for diabetes mellitus) can increase the absorption of both medications.

Interactions with Food and Herbal Supplements

• Food and herbal supplements can also interact with medications.

Examples of Food and Supplement Interactions

• Food and Zolpidem:

  • Food delays the absorption of zolpidem (Ambien), which postpones the onset of sleep.

• Grapefruit Juice:

  • Grapefruit juice interacts with many medications, increasing their levels in the bloodstream.

  • Example: Atorvastatin.

• St. John's Wort:

  • St. John's Wort, used for depression, can reduce the effectiveness of birth control pills, which increases the risk of pregnancy.

Interactions with Oral Contraceptives

• Specific medications can reduce the effectiveness of oral contraceptives.

Examples of Medications That Interfere with Oral Contraceptives

• Antibiotics: Penicillins

• Anticonvulsants: Phenytoin (Dilantin)

• Antifungals: Fluconazole (Diflucan)