|Year : 2013 | Volume
| Issue : 3 | Page : 185-188
Myofibrosis in a pentazocine addict
Paresh Zanzmera, Manoj Somasekharan, Achal Srivastava
All India Institute of Medical Sciences, New Delhi, India
|Date of Web Publication||7-Jan-2014|
Department of Neurology, Sree Chitra Institute for Medical Sciences and Technology, Trivandrum, Thiruvananthapuram, Kerala
Source of Support: None, Conflict of Interest: None
Pentazocine, a synthetic narcotic analgesic, is commonly used for the relief of moderate to severe pain, but has been rarely abused also. It is usually well tolerated; however, adverse effects are not uncommon, when higher doses are used, especially in a dependent fashion. There are reports of various complications associated with its use, including skin fibrosis, skin ulceration, abnormal skin pigmentation and symmetrical myopathy with fibrous myopathy. Fibrosis has usually been reported in the muscles at the site of injection of the drug. Being opioid in nature, it has a high abuse potential. We report a case of pentazocine-induced myofibrosis in a 33-year-old man involving muscles which were not injected with pentazocine. This case highlights the care that needs to be taken when prescribing opioid analgesics, such as pentazocine, as routine painkillers. Rare consequences such as myofibrosis are devastating and can cause significant lifelong disability.
Keywords: Addiction, myofibrosis, pentazocine
|How to cite this article:|
Zanzmera P, Somasekharan M, Srivastava A. Myofibrosis in a pentazocine addict. Indian J Pain 2013;27:185-8
| Introduction|| |
Pentazocine is a synthetic narcotic analgesic. It is commonly used for the pain relief of moderate to severe pain secondary to various conditions, but also rarely abused.  The side effects and complications of its use could be skin fibrosis, skin ulceration, abnormal skin pigmentation, symmetrical myopathy , and fibrous myopathy (a rare complication following prolonged pentazocine injection). , Fibrosis has been reported in the muscles at the site of injection of the drug. The association of myopathy with contractures around the shoulder and hip joints is also described previously. , Pentazocine-induced myofibrosis mainly involves muscles around elbow and knee joints along with hip and shoulder joints following long-standing pentazocine abuse.  This case reports pentazocine-induced myofibrosis involving muscles around ankle joints in association with the hip, shoulder, elbow and knee joints following pentazocine addiction.
| Case Report|| |
A 33-year-old man presented with complaints of painless and progressive bilaterally symmetrical toe walking with stiffness and wasting of the muscles of both calves, followed by bilateral elbow contracture and then stiffness and wasting of back and proximal muscles of both upper limbs for the previous 3½ years. There was significant impairment of his daily activities including walking, bending, lifting, or straightening arms. Patient had retained ambulation till now and due to contracture of the bilateral shoulder, elbow, hip, knee and ankle joints along with lordosis of lumbar spine; resulting in characteristic 'robotic' posture with 'toe walking'. There was no associated weakness.
At 17 years of age, he was prescribed long-acting benzodiazepines, valium (Diazepam) 10 mg and nitravate (Nitrazepam) 10 mg by general practitioner for pain relief and insomnia. Over a period of time, he developed drug dependency. From 23 years onwards, he started self-injecting Fortwin (Pentazocine) and Phenergan (Promethazine) combination in a dependent fashion, around two ampules every day in divided doses, into the buttocks and upper arms. He never injected into thighs, calves, abdominal, shoulder girdle or forearm muscles. He would develop generalized tonic-clonic seizures and restlessness in absence of drugs.
On examination, his vitals were stable but he had great difficulty in dorsiflexion of ankles and extension of elbow, along with overhead abduction and complete adduction of shoulders. There was wasting and hardening of the muscles of the back, arms, thighs, forearm, and calf muscles [Figure 1] and [Figure 2]. He walked with a lordotic posture and robotic gait and had marked woody indurations of the deltoids, biceps, glutei and quadriceps, and gastrocnemius. The range of movements was decreased markedly. His arms could not be actively abducted beyond 75° and the legs not more than 60°. Both elbows were semi-flexed with no more than a 25° range of movement. He was unable to touch heels on floor with ankle range of movement nearly 10°. There was associated bilateral wrist joint contracture with range of movement not more than 40°. Movements at the distal joints in both upper and lower limbs were significantly affected as compared to proximal muscles. Muscle power was normal within the limited range of movements, and there was no sensory deficit. Examination of the rest of the nervous and other systems did not reveal any other abnormalities.
|Figure 1: Front view of patient. Note partly abducted shoulders, semifl exed elbows, and planter flexed ankles|
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|Figure 2: Lateral view of patient. Note lumbar lordosis, incomplete extension of knees and planter flexed ankles. Figure 1 and 2 shows robot-like posture of patient|
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On investigation, hemogram, liver and renal function tests, serum calcium, phosphate, and creatinine phosphokinase were within the normal ranges. Roentgenogram of the lumbar-sacral spine, thigh, knee, chest, shoulder, elbow, and cervical spine showed multiple soft tissue calcifications with hyperdensity of muscles [Figure 3]. MRI thigh [Figure 4] revealed non-descript reduced signal intensities in subcutaneous fascia and myofascium in all groups of muscles of thigh. There was no articular abnormality. Electromyographic examination of muscles was normal. Muscle biopsy showed atrophy with features suggestive of neurogenic involvement without active inflammatory signs.
|Figure 3: X-ray right elbow AP view showing hyperdensity of muscles. There is no body abnormality seen|
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|Figure 4: MRI of right thigh, axial section showed non-descript reduced signal intensities in subcutaneous fascia and myofascium in all groups of muscles of thigh|
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| Discussion|| |
The differential diagnoses considered were ankylosing spondylitis, Stiff-man syndrome, myositis ossificans, and parathyroid disease. In view of normal joints, diagnosis of ankylosing spondylitis was not considered further. Stiff-man syndrome presents with spasms and cramps, and usual presentation is after middle age. The possibility of myositis ossificans was unlikely, as the present case was of late onset and was characterized by the absence of skeletal abnormality. Normal serum calcium and phosphate levels excluded hypoparathyroidism. Pentazocine-induced myofibrosis was a strong possibility in view of the history of pentazocine abuse, hardened muscles and the clinical presentation.
Previous case reports described complications of pentazocine injections in form of browny induration of skin and under-lying tissues , and fibrous myopathy , with patients having woody induration of muscles with secondary contractures.
The exact mechanism of this condition is unknown. Pentazocine is acidic (pH 4.3) in nature and its crystals gets precipitated in neutral or alkaline medium. This property, along with the muscle trauma caused by repeated needling and rapid injections of large boluses of drugs, may be responsible for this or other types of drug-induced myopathy.  This remains the most acceptable hypothesis for explanation of the condition. The use of pentazocine in this case was along with phenergan injection. This could have played a contributory role to the pathogenesis, phenomenon, although we do not consider it as the primary causative agent since its use has not been associated with such lesions in the literature.
Previous reports  of pentazocine-induced myofibrosis had predominant involvement of proximal muscles, as contrast to predominant distal muscles involvement in our case. Specifically, toe walking due to pentazocine-induced myofibrosis is novel presentation. Another interesting aspect of this case is the involvement of muscle groups which were not injected with pentazocine. The patient's self-reported history and the inaccessibility of the muscle groups involved (those of the shoulder blade, back muscles) support the claim that these muscle groups were not directly injected by the patient. Hence, the local action of pentazocine seems to be an unlikely explanation of the condition. The possible mechanism could be a direct action of the drug once it enters into the circulation or the release of an independent factor from the site of injection that leads to widespread involvement of the muscles.
Moreover, the onset of the fibrotic changes correlated to the use of the injection pentazocine and was temporally unrelated to the past use of benzodiazepam, as the patient and his family members corroborated that he had stopped benzodiazepam use at least 8 years ago. Moreover, we could find no complications caused by long-term dependence of benzodiazepam.
The abuse of prescription opioids, such as pentazocine, is being increasingly reported across globe  including India. ,, With easily over-the-counter access to these drugs in India and many developing countries, awareness of this complication is important so that unwanted side effects can be avoided. Moreover, the drugs are initially prescribed for a medical indication and subsequent use by the patient continues without the advice of a physician. Clinicians should be aware of addictive property of such medicine, and extra caution should be exercised when dealing with individuals with a history of substance abuse and/or dependence. This will help in preventing such drug abuse and its complications.
In conclusion, this case highlights the rare consequence such as myofibrosis following pentazocine addiction resulting in to lifelong disability. Physician should be aware and vigilant about prescribing potentially addictive painkillers.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]