Tenofovir Overdosage-A Rarely Reported Phenomenon in Literature

Introduction: Hepatitis B virus (HBV) has infected affected thirty three percent of the world population, two billion have been infected worldwide and out of them, 350 million suffer from chronic HBV infection. Out of these, approximately 15–40% of patients will develop cirrhosis, liver failure and hepatocellular carcinoma. The most common side effects of tenofovir are nausea, vomiting, diarrhea, bloating, flatulence, indigestion, loss of appetite, headache, weakness (asthenia), dizziness, insomnia, rash, itching, back pain, pain, renal failure, lactic acidosis, alopecia and osteoporosis. There is paucity of research regarding overdosage of tenofovir. Hence, the need of this case report. Case Report: We are reporting a thirty-year-old male of chronic hepatitis B who was in active phase thus was put on Tenofovir disoproxil fumarate (TDF) 300 mg daily once. The six -month therapy was issued to him free of cost under National viral hepatitis control program (NVHCP). As the six bottles of tenofovir were of different time period of expiry, hence they were numbered from 1-6, for ease of patient, so that number 1 bottle is finished first and number 6 was to be taken in last. It was clearly explained to him that only one tablet has to be taken in a day. There were no accompanying family members at the time of dispensing of drugs. The patient reported after one month with complaints of irritability, vertigo, restlessness, red eyes, feeling of radiation of heat from body and headache. We have never seen these kinds of side effects with tenofovir in 2500 patients in last 13 years who are on regular treatment and follow-up. There was no history of any kind of drug intake with tenofovir, alteration in food habits, any kind of drug or alcohol abuse in last one month when tenofovir was started. On probing further, he admitted that he was taking six tablets of tenofovir per day. The reason given was that by mistake on reading number 6 written on one bottle, he understood that six tablets per day are to be taken in a day. The reality is that number 6 was written on that particular bottle for depicting that this bottle has to be used in last i.e. in sixth month. The patient all biochemical labs including liver function & renal function, blood sugar, thyroid profile, serum electrolytes, serum calcium and phosphorus levels, urine complete examination, ECG, chest x-ray and ultrasonogram abdomen was essentially normal. He was immediately shifted on daily once dosage of tenofovir. All his symptoms subsided within a week. Conclusion: Every drug has well documented side effects but it is not necessary that manifestations due to overdosage are available for all the available drugs. Similarly, there is scarcity of data regarding overdose of tenofovir which occurred in our case. The relieving side was that patient did not develop life threatening complications like lactic acidosis and renal failure. Our case report re-affirms the need of repeatedly explaining to the patients about proper dosage of drugs.