Correspondence Address:
Saumitra Shankar Nemlekar
Institute of Psychiatry and Human Behavior, Bambolim - 403 202, Goa
India

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Sir,

Diphenoxylate, a weak μ-opioid receptor agonist, has been considered as a drug of low abuse potential.[1] It was marketed as an over-the-counter (OTC) antidiarrheal in combination with atropine. This metonymic term OTC is used to describe other such medicines which can be procured by a patient directly. Such availability has been argued to offer benefits in terms of convenient access to and choice of medicines as well as involving individuals as active participants in their own health and the treatment of illness. OTC medicine abuse is a recognized problem internationally but is currently incompletely understood.[2] Many physicians seem unaware either of the opioid pharmacological structure of diphenoxylate hydrochloride or of its consequent potential for abuse and dependency.

Each tablet for oral use contained diphenoxylate hydrochloride 2.5 mg and atropine sulfate 0.025 mg. The subtherapeutic amount of atropine sulfate is present to discourage deliberate overdosage.[3] Its antidiarrheal mechanism is by a direct action on the smooth muscle, by the μ-opioid agonistic action, resulting in enhanced segmentation leading to consequent increase in transit time.[2] It crosses the blood–brain barrier, acting on central μ-opioid receptors and therefore habit forming.[1] It is metabolized by ester hydrolysis and half-life is 12–14 h. There are experienced users who have used it as substitute.[1],[4],[5] We hereby present a case of diphenoxylate dependence detoxified with buprenorphine and naloxone combination.

AJ, a 28-year-old married male presented with dependence on diphenoxylate tablets. Previously, he used opium husk and later had shifted to diphenoxylate tablets. The use of tablets started with 25 tablets per day as advised by other opioid using peers. Patient developed tolerance within 6 weeks. He increased the frequency of use to twice a day and then three times a day. The total number of tablets also increased. At presentation, he reported daily oral use of 110 tablets of lomotil (diphenoxylate hydrochloride 2.5 mg and atropine sulfate 0.025 ug), a total diphenoxylate of 275 mg/day to control his withdrawals and craving. The cumulative dose of atropine was 2.75 mg. On stopping the tablets, he experienced intense pain in calves, perspiration, generalized weakness, watering from eyes, and congestion of nose. He reported these within an hour of his usual time. At presentation, his Clinical Opioid Withdrawal Scale score was 14 while Subjective Opioid Withdrawal Scale score was 11. No atropine effects were noted.

The patient opted for outpatient basis treatment. The patient was started on buprenorphine 2 mg + naloxone 0.5 mg combination. The patient required clonazepam 0.5 mg at night for sleep disturbance, in spite of resolution of withdrawal. After 7 days, the patient did not show residual withdrawal features; Clinical Opioid Withdrawal Scale score was 3 and Subjective Opioid Withdrawal Scale score was 3. At 1 month, buprenorphine was reduced to 2 mg/day. At 3 months, he was maintaining well on 2 mg buprenorphine. Further plan will be to discontinue the medications.

The patient had moderate opioid withdrawal at presentation and was unwilling for indoor treatment. In our case to achieve deaddiction, buprenorphine and naloxone combination [6] was chosen. Buprenorphine has a ceiling effect to opioid response with naloxone added as deterrent against intravenous abuse of the tablet, as opioid users are known to shift through the various formulations over time.[7] The use of buprenorphine and naloxone combination is a safe and effective domiciliary detoxification in such patients, inarguably at a lower abuse potential.

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Conflicts of interest

There are no conflicts of interest.

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