7 Interactions found for:
Drug Interactions
No drug interactions were found for selected drugs: aspirin, Synthroid.
This does not necessarily mean no interactions exist. Always consult your healthcare provider.
Drug and Food Interactions
Moderate
Synthroid
+ Food
The following applies to the ingredients: Levothyroxine (found in Synthroid)
ADJUST DOSING INTERVAL: Consumption of certain foods as well as the timing of meals relative to dosing may affect the oral absorption of T4 thyroid hormone (i.e., levothyroxine). T4 oral absorption is increased by fasting and decreased by foods such as soybean flour (e.g., infant formula), cotton seed meal, walnuts, dietary fiber, calcium, and calcium fortified juices. Grapefruit or grapefruit products may delay the absorption of T4 thyroid hormone and reduce its bioavailability. The mechanism of this interaction is not fully understood.
MANAGEMENT: Some manufacturers recommend administering oral T4 as a single daily dose, on an empty stomach, one-half to one hour before breakfast. In general, oral preparations containing T4 thyroid hormone should be administered on a consistent schedule with regard to time of day and relation to meals to avoid large fluctuations in serum levels. Foods that may affect T4 absorption should be avoided within several hours of dosing if possible. Consult local guidelines for the administration of T4 in patients receiving enteral feeding.
References
- "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical PROD (2002):
- "Product Information. Armour Thyroid (thyroid desiccated)." Forest Pharmaceuticals (2022):
- Wohlt PD, Zheng L, Gunderson S, Balzar SA, Johnson BD, Fish JT "Recommendations for the use of medications with continuous enteral nutrition." Am J Health Syst Pharm 66 (2009): 1438-67
The following applies to the ingredients: Levothyroxine (found in Synthroid)
ADJUST DOSING INTERVAL: Concurrent administration of calcium-containing products may decrease the oral bioavailability of levothyroxine by one-third in some patients. Pharmacologic effects of levothyroxine may be reduced. The exact mechanism of interaction is unknown but may involve nonspecific adsorption of levothyroxine to calcium at acidic pH levels, resulting in an insoluble complex that is poorly absorbed from the gastrointestinal tract. In one study, 20 patients with hypothyroidism who were taking a stable long-term regimen of levothyroxine demonstrated modest but significant decreases in mean free and total thyroxine (T4) levels as well as a corresponding increase in mean thyrotropin (thyroid-stimulating hormone, or TSH) level following the addition of calcium carbonate (1200 mg/day of elemental calcium) for 3 months. Four patients had serum TSH levels that were higher than the normal range. Both T4 and TSH levels returned to near-baseline 2 months after discontinuation of calcium, which further supported the likelihood of an interaction. In addition, there have been case reports suggesting decreased efficacy of levothyroxine during calcium coadministration. It is not known whether this interaction occurs with other thyroid hormone preparations.
MANAGEMENT: Some experts recommend separating the times of administration of levothyroxine and calcium-containing preparations by at least 4 hours. Monitoring of serum TSH levels is recommended. Patients with gastrointestinal or malabsorption disorders may be at a greater risk of developing clinical or subclinical hypothyroidism due to this interaction.
References
- Schneyer CR "Calcium carbonate and reduction of levothyroxine efficacy." JAMA 279 (1998): 750
- Singh N, Singh PN, Hershman JM "Effect of calcium carbonate on the absorption of levothyroxine." JAMA 283 (2000): 2822-5
- Csako G, McGriff NJ, Rotman-Pikielny P, Sarlis NJ, Pucino F "Exaggerated levothyroxine malabsorption due to calcium carbonate supplementation in gastrointestinal disorders." Ann Pharmacother 35 (2001): 1578-83
- Neafsey PJ "Levothyroxine and calcium interaction: timing is everything." Home Healthc Nurse 22 (2004): 338-9
Moderate
Aspirin
+ Food
The following applies to the ingredients: Aspirin
GENERALLY AVOID: The concurrent use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) and ethanol may lead to gastrointestinal (GI) blood loss. The mechanism may be due to a combined local effect as well as inhibition of prostaglandins leading to decreased integrity of the GI lining.
MANAGEMENT: Patients should be counseled on this potential interaction and advised to refrain from alcohol consumption while taking aspirin or NSAIDs.
References
- "Product Information. Motrin (ibuprofen)." Pharmacia and Upjohn PROD (2002):
Minor
Aspirin
+ Food
The following applies to the ingredients: Aspirin
One study has reported that coadministration of caffeine and aspirin lead to a 25% increase in the rate of appearance and 17% increase in maximum concentration of salicylate in the plasma. A significantly higher area under the plasma concentration time curve of salicylate was also reported when both drugs were administered together. The exact mechanism of this interaction has not been specified. Physicians and patients should be aware that coadministration of aspirin and caffeine may lead to higher salicylate levels faster.
References
- Yoovathaworn KC, Sriwatanakul K, Thithapandha A "Influence of caffeine on aspirin pharmacokinetics." Eur J Drug Metab Pharmacokinet 11 (1986): 71-6
Drug and Pregnancy Interactions
Major
Aspirin
+ Pregnancy
The following applies to the ingredients: Aspirin
100 mg/day or less: Use with caution
Greater than 100 mg/day: NSAIDs should be avoided at 20 weeks gestation and later
AU TGA pregnancy category: C
US FDA pregnancy category: Not Assigned
Risk Summary: Nonsteroidal anti-inflammatory drugs (NSAIDs) use in pregnant women at 30 weeks gestation and later may cause premature closure of the fetal ductus arteriosus; NSAID use at 20 weeks gestation or later may cause fetal renal dysfunction leading to oligohydramnios and, in some cases, neonatal renal impairment.
Comments:
-Guidelines recommend low-dose aspirin prophylaxis (e.g., 81 mg/day) in women at high risk of preeclampsia; initiation should be between 12- and 28-weeks gestation (optimally before 16 weeks) and continued until delivery; the use aspirin at 81 mg/day dose for certain pregnancy-related conditions at any point in pregnancy is an exception to the FDA recommendations to avoid use of NSAIDs in pregnancy at 20 weeks or later.
-If NSAID use is necessary between 20- and 30-weeks' gestation, limit use to the lowest effective dose for the shortest duration possible; ultrasound monitoring of amniotic fluid should be considered if NSAID use extends beyond 48 hours; if oligohydramnios occurs, discontinue NSAID and treat appropriately.
-NSAID use is not recommended in women attempting to conceive as it may impair female fertility.
In animals, prostaglandin synthesis inhibitors have been shown to increase pre and post-implantation loss and embryo-fetal lethality. Epidemiologic studies suggest increased risk of miscarriage, cardiac malformations, and gastroschisis when used early in pregnancy; the absolute risk of cardiovascular malformations increased from less than 1% to up to approximately 1.5%. The risk is believed to increase with dose and duration of therapy.
Aspirin (acetylsalicylic acid) is a NSAID that inhibits cyclooxygenase (COX) isoenzymes 1 and 2. The effect on COX isoenzymes is dose-dependent with lower doses (60 to 150 mg) inhibiting platelet synthesis while higher doses results in inhibition of both COX-1 and COX-2 blocking all prostaglandin production. Low-dose aspirin has been used during pregnancy to prevent or delay the onset of preeclampsia. Daily low-dose aspirin has been shown to be associated with a low likelihood of serious maternal, or fetal complications. Guidelines should be consulted for specific use.
During the third trimester of pregnancy, administration of COX-1 and COX-2 blocking nonsteroidal anti-inflammatory drugs (NSAIDs) may cause premature closure of the fetal ductus arteriosus, oligohydramnios, fetal renal impairment, pulmonary hypertension, and prolongation of bleeding time. There are no controlled data in human pregnancy.
US FDA Drug Safety Communication (10-2020): The FDA is requiring a new warning be added to NSAID labeling describing the risk of fetal kidney problems that may result in low amniotic fluid. The FDA is recommending pregnant women avoid NSAID use at 20 weeks gestation or later; the use aspirin at 81 mg/day dose for certain pregnancy-related conditions at any point in pregnancy is an exception. Through 2017, the FDA has received 35 reports of low amniotic fluid levels or kidney problems in mothers who took NSAIDs while pregnant. Five newborns died; 2 had kidney failure and confirmed low amniotic fluid, 3 had kidney failure without confirmed low amniotic fluid. The low amniotic fluid started as early as 20 weeks of pregnancy. There were 11 reports of low amniotic fluid levels during pregnancy and the fluid volume returned to normal after the NSAID was stopped. The medical literature has reported low amniotic fluid levels with use of NSAIDs for varying amounts of time, ranging from 48 hours to multiple weeks. Complications of prolonged oligohydramnios may include limb contractures and delayed lung maturation. In some postmarketing cases of impaired neonatal renal function, invasive procedures such as exchange transfusion or dialysis were required. In other cases, the condition was reversible within 3 to 6 days of stopping the NSAID and in these cases reappeared when the same NSAID was restarted.
Administration during labor and delivery is not recommended as the onset of labor may be delayed and duration increased with greater bleeding tendency in mother and child.
A study of the use of low-dose aspirin (60 mg per day) to prevent and treat preeclampsia in 9364 pregnant women (the Collaborative Low-dose Aspirin Study in Pregnancy--CLASP) did "not support routine prophylactic or therapeutic administration of antiplatelet therapy in pregnancy to all women at increased risk of preeclampsia or IUGR." In that study, no excess of intraventricular hemorrhage, neonatal bleeds, or mortality attributable to bleeding were observed. The investigators did identify a possible role for low-dose aspirin in the treatment of early-onset preeclampsia severe enough to need very preterm delivery.
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 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
- "Clasp: a randomised trial lf low-dose aspirin for the prevention and treatment of pre-eclampsia among 9364 pregnant women." Lancet 343 (1994): 619-29
- Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
- Cerner Multum, Inc. "Australian Product Information." O 0
- US Food and Drug Administration "TITLE 21--FOOD AND DRUGS,CHAPTER I--FOOD AND DRUG ADMINISTRATION,DEPARTMENT OF HEALTH AND HUMAN SERVICES SUBCHAPTER D--DRUGS FOR HUMAN USE,PART 341 COLD, COUGH, ALLERGY, BRONCHODILATOR, AND ANTIASTHMATIC DRUG PRODUCTS FO. https://www.accessdata.fda.gov" (2016):
- Committee on Obstetric Practice Society for Maternal-Fetal Medicine "ACOG Committee Opinion No. 743: Low-dose aspirin use during pregnancy." Obstet Gynecol 132 (2018): e44-e52
Minor
Synthroid
+ Pregnancy
The following applies to the ingredients: Levothyroxine (found in Synthroid)
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
Aspirin
+ Breastfeeding
The following applies to the ingredients: Aspirin
Benefit should outweigh risk
Excreted into human milk: Yes
Comments:
-This drug appears compatible with breastfeeding for occasional use and in low doses for anti-thrombosis; however, repeated use in normal doses and long-term use, especially in high doses should be avoided.
-Breastfed infants should be monitored for hemolysis, prolonged bleeding time, and metabolic acidosis.
This drug is excreted in human milk in small amounts. Low dose aspirin (75 to 162 mg/day) is considered by many experts to be compatible with breastfeeding. Peak milk salicylate levels have been reported up to 9 hours after maternal dosing with peak levels generally occurring 2 to 6 hours after nursing. Large doses may result in rashes, platelet abnormalities, and bleeding in nursing infants. Long-term, high dose maternal use was associated with 1 case of metabolic acidosis in breastfed infant. The risk for Reye's syndrome in infants with viral infections is unknown.
References
- Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
- United States National Library of Medicine "Toxnet. Toxicology Data Network. http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT" (2013):
- Department of Adolescent and Child Health and Development. UNICEF. World Health Organization "Breastfeeding and maternal medication: recommendations for drugs in the eleventh Who model list of essential drugs. http://whqlibdoc.who.int/hq/2002/55732.pdf?ua=1" (2014):
- US Food and Drug Administration "TITLE 21--FOOD AND DRUGS,CHAPTER I--FOOD AND DRUG ADMINISTRATION,DEPARTMENT OF HEALTH AND HUMAN SERVICES SUBCHAPTER D--DRUGS FOR HUMAN USE,PART 341 COLD, COUGH, ALLERGY, BRONCHODILATOR, AND ANTIASTHMATIC DRUG PRODUCTS FO. https://www.accessdata.fda.gov" (2016):
Minor
Synthroid
+ Breastfeeding
The following applies to the ingredients: Levothyroxine (found in Synthroid)
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: Consumer 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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