7 Interactions found for:
Drug Interactions
Minor
Metoprolol
+ Synthroid
The following applies to the ingredients: Metoprolol and Levothyroxine (found in Synthroid)
Professional Content
Thyroid hormone therapy may reverse the decreased hepatic blood flow that is associated with hypothyroidism. Increased hepatic metabolism and decreased serum levels of some beta-adrenergic antagonists may result. In addition, beta-adrenergic antagonists may decrease the peripheral conversion of thyroxine to its active form triiodothyronine. When hypothyroidism is converted to a euthyroid state, a decrease in beta-antagonist effectiveness is possible. No special precautions are necessary.
References
- Wells PG, Feely J, Wilkinson GR, Wood AJ "Effect of thyrotoxicosis on liver blood flow and propranolol disposition after long-term dosing." Clin Pharmacol Ther 33 (1983): 603-8
- Aro A, Antila M, Korhonen T, Sundquist H "Pharmacokinetics of propranolol and sotalol in hyperthyroidism." Eur J Clin Pharmacol 21 (1982): 373-7
- "Product Information. Levothyroxine Sodium (levothyroxine)." Lannett Company Inc (2024):
- "Product Information. Levothyroxine Sodium (levothyroxine)." Zentiva Pharma UK Ltd (2023):
- "Product Information. Levothyroxine (Sandoz) (levothyroxine sodium)." Sandoz Pty Ltd (2023):
Drug and Food Interactions
Moderate
Metoprolol
+ Food
The following applies to the ingredients: Metoprolol
Food can enhance the levels of metoprolol in your body. You should take metoprolol at the same time each day, preferably with or immediately following meals. This will make it easier for your body to absorb the medication. Avoid drinking alcohol, which could increase drowsiness and dizziness while you are taking metoprolol. Metoprolol is only part of a complete program of treatment that also includes diet, exercise, and weight control. Follow your diet, medication, and exercise routines very closely.
The following applies to the ingredients: Metoprolol
Using metoprolol together with multivitamin with minerals may decrease the effects of metoprolol. Separate the administration times of metoprolol and multivitamin with minerals by at least 2 hours. If your doctor does prescribe these medications together, you may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.
Moderate
Synthroid
+ Food
The following applies to the ingredients: Levothyroxine (found in Synthroid)
The timing of meals relative to your oral levothyroxine dose can affect the absorption of the medication. Therefore, levothyroxine should be taken on a consistent schedule with regard to time of day and relation to meals to avoid large fluctuations in blood levels, which may alter its effects. In addition, absorption of levothyroxine may be decreased and/or delayed by foods such as soybean flour, cotton seed meal, walnuts, dietary fiber, calcium, calcium fortified juices and grapefruit or grapefruit juice. These foods should be avoided within several hours of dosing if possible. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.
The following applies to the ingredients: Levothyroxine (found in Synthroid)
Using multivitamin with minerals together with levothyroxine may decrease the effects of levothyroxine. You should separate the administration of levothyroxine and multivitamin with minerals by at least 4 hours. If your doctor does prescribe these medications together, you may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.
Drug and Pregnancy Interactions
Major
Metoprolol
+ Pregnancy
The following applies to the ingredients: Metoprolol
Professional Content
US: This drug should be used during pregnancy only if clearly needed.
AU and UK: Use is not recommended unless benefit outweighs risk; if used during pregnancy, administer the lowest possible dose and discontinue at least 2 to 3 days prior to expected delivery, if possible.
AU TGA pregnancy category: C
US FDA pregnancy category: C
Animal studies have revealed increased postimplantation loss, fetolethality, and decreased neonatal survival. There are no controlled data in human pregnancy.
AU TGA pregnancy category C: Drugs which, owing to their pharmacological effects, have caused or may be suspected of causing, harmful effects on the human fetus or neonate without causing malformations. These effects may be reversible. Accompanying texts should be consulted for further details.
US FDA pregnancy category C: Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.
References
- "Product Information. Lopressor (metoprolol)." Novartis Pharmaceuticals PROD (2001):
- Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
- Cerner Multum, Inc. "Australian Product Information." O 0
Minor
Synthroid
+ Pregnancy
The following applies to the ingredients: Levothyroxine (found in Synthroid)
Professional Content
Use is considered acceptable
AU TGA pregnancy category: A
US FDA pregnancy category: Not Assigned
Risk Summary: No increased rates of major birth defects or miscarriages have been reported with use during pregnancy; untreated hypothyroidism during pregnancy is associated with risks to the mother and fetus
Comments:
-Thyroid replacement therapy should not be discontinued during pregnancy; hypothyroidism diagnosed during pregnancy should be promptly treated.
-Monitor TSH levels and adjust doses as needed.
Animal studies have not been conducted. There is a long history of using this drug in pregnant women and this experience has not shown increased rates of fetal malformations, miscarriages or other adverse maternal or fetal outcomes. Hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, pre-eclampsia, stillbirth and premature delivery. Maternal hypothyroidism may have an adverse effect on fetal neurocognitive development. Pregnant women taking this drug should have their TSH measured during each trimester and dose adjusted as appropriate. Patients will generally return to their pre-pregnancy dose after delivery. There are no controlled data in human pregnancy.
AU TGA pregnancy category A: Drugs which have been taken by a large number of pregnant women and women of childbearing age without any proven increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed.
US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.
References
- "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical PROD (2002):
- Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
- Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online. http://www.appco.com.au/appguide/default.asp" (2006):
- Cerner Multum, Inc. "Australian Product Information." O 0
Drug and Breastfeeding Interactions
Major
Metoprolol
+ Breastfeeding
The following applies to the ingredients: Metoprolol
Professional Content
AU and UK: Use is not recommended unless benefit outweighs risk.
US: This drug has been used without apparent harmful effects; caution is recommended.
Excreted into human milk: Yes (in small amounts)
Comments: This drug has been used without apparent harmful effects in the nursing infant.
An infant consuming 1 L of breast milk a day would receive a dose of less than 1 mg of drug.
References
- "Product Information. Lopressor (metoprolol)." Novartis Pharmaceuticals PROD (2001):
- Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
- Cerner Multum, Inc. "Australian Product Information." O 0
Minor
Synthroid
+ Breastfeeding
The following applies to the ingredients: Levothyroxine (found in Synthroid)
Professional Content
Use is considered acceptable
Excreted into human milk: Yes
Comments:
-Levothyroxine (T4) is a normal component of human milk; limited data on exogenous replacement doses during breastfeeding have not shown an adverse effect in nursing infants.
-Levothyroxine dose requirements may be increased in the postpartum period compared to prepregnancy requirements in patients with Hashimoto's thyroiditis.
-The presence of thyroid hormone in breast milk does not appear to interfere with neonatal thyroid screening.
References
- "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical PROD (2002):
- Jansson L, Ivarsson S, Larsson I, Ekman R "Tri-iodothyronine and thyroxine in human milk." Acta Paediatr Scand 72 (1983): 703-5
- Moller B, Bjorkhem I, Falk O, Lantto O, Lafsson A "Identification of thyroxine in human breast milk by gas chromatography-mass spectrometry." J Clin Endocrinol Metab 56 (1983): 30-4
- Mizuta H, Amino N, Ichihara K, et al. "Thyroid hormones in human milk and their influence on thyroid function of breast-fed babies." Pediatr Res 17 (1983): 468-71
- Hahn HB, Spiekerman AM, Otto R, Hossalla DE "Thyroid function tests in neonates fed human milk." Am J Dis Child 137 (1983): 220-2
- Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
- Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online. http://www.appco.com.au/appguide/default.asp" (2006):
- Cerner Multum, Inc. "Australian Product Information." O 0
- United States National Library of Medicine "Toxnet. Toxicology Data Network. http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT" (2013):
Therapeutic Duplication Warnings
No warnings were found for your selected drugs.Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.
Switch to: Professional Interactions
| Drug Interaction Classification | |
|---|---|
These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication. |
|
| Major | Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. |
| Moderate | Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. |
| Minor | Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan. |
| Unknown | No interaction information available. |
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