Vomiting after taking the drug, do I need to take an extra dose?

Article by Pharmacist, Master Nguyen Hoang Phuong Khanh - Clinical Pharmacist - Faculty of Pharmacy - Vinmec Central Park International General Hospital

In fact, several factors can be considered to consider resuming the drug after vomiting such as: medical condition, pharmacokinetic characteristics, therapeutic window and drug side effects. In case of questions, you should contact your doctor or pharmacist for detailed advice.
In general, medication can be replenished when it is clear that the drug is in the vomit or vomit within 15 minutes of taking the drug. Where the drug has been taken for more than 15 minutes, the following factors can be assessed:
Consider re-administration when missing a dose severely affects the course of treatment:
Example of encouraging resumption of hepatitis C medication , HIV, antibiotics to treat acute infections, especially with single dose drugs such as azithromycin to treat gonorrhea. For progestin-only oral contraceptives or emergency oral contraceptives, it should be restarted if vomiting occurs within 3 hours.

In the following cases, the patient does not need to take the drug again after vomiting:
When taking more drugs can lead to side effects such as: diabetes drugs can cause hypoglycemia, antihypertensive drugs cause blood pressure. lowering blood pressure ... When missing 1 dose does not affect the outcome of treatment as lipid therapy drugs. Drugs with a narrow therapeutic range: anticoagulants, methotrexate, phenytoin, digoxin. Drugs with prolonged half-life: amiodarone, fluoxetine Drugs that are rapidly absorbed into the body eg sublingual agents, liquid drugs. In addition, cases need to consult a doctor, pharmacist such as:
Oral chemotherapy drugs, anti-rejection drugs ... In case the patient vomits many times, leading to missed doses. The information in the article above that the patient can consider whether to take medicine after vomiting or not. Accordingly, to ensure the effectiveness of treatment, it is best for patients to consult a doctor or pharmacist before using it.
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References:
Evaluate Whether to Redose Meds After Vomiting – Pharmacist’s letter Kendrick JG, Ma K, Dezorzi P, Hamilton D. Vomiting of oral medications by pediatric patients: survey of medication redosing practices. Can J Hosp Pharm. 2012;65(3):196-201. doi:10.4212/cjhp.v65i3.1142 Medsafe. I've missed a dose; what should i do? May 2003. https://www.medsafe.govt.nz/profs/PUarticles/missed.htm. (Accessed August 2, 2019).