Spasmend combines paracetamol 500 mg with mephenesin 150 mg — a painkiller plus a muscle relaxant. It is used for painful muscle spasm: acute back and neck pain, stiff neck, and muscular pain after strain. It causes drowsiness, and it contains paracetamol, so do not take other paracetamol with it.
What is Spasmend?
Spasmend is registered in South Africa as Schedule 2, available from a pharmacist:
| Contains | Per tablet |
|---|---|
| Paracetamol | 500 mg |
| Mephenesin | 150 mg |
The two ingredients address different halves of the same problem.
Paracetamol relieves pain and reduces fever, acting mainly within the central nervous system. It has little effect on inflammation.
Mephenesin is a centrally acting muscle relaxant. Like methocarbamol, it does not act on muscle directly — it works in the spinal cord, depressing transmission in the reflex pathways that maintain muscle tone. The muscle relaxes because the signal telling it to contract is reduced. That is why the notable side effect is drowsiness rather than general weakness.
Mephenesin is one of the older muscle relaxants — methocarbamol was in fact developed from it — and it is relatively short-acting, which is why it is usually taken several times daily.
The combination targets the pain–spasm cycle, a specific and common problem. An injured or strained muscle goes into spasm; the spasm causes pain; pain provokes further protective spasm. Left alone the loop sustains itself long after the original injury would have settled. Relieving pain and reducing spasm together interrupts it more effectively than either alone.
This is why it is aimed at muscular pain specifically — not at general aches, headache or inflammatory joint pain. For pain without spasm, plain paracetamol or an anti-inflammatory is more appropriate, and will not sedate you.
What is Spasmend commonly used for?
- Acute low back pain with muscle spasm.
- Neck pain and stiff neck, including after awkward sleeping or whiplash-type strain.
- Muscle spasm after injury or strain.
- Muscular pain in the shoulders and upper back, often tension-related.
- Fibrositis and muscular rheumatism, for short-term relief.
- Painful muscle conditions where spasm is a significant part of the problem.
It is intended for short-term use — typically a few days to a couple of weeks. Muscle relaxants generally work best in the acute phase, and their benefit fades while the drowsiness continues.
Movement matters more than most people expect. For acute back pain, current advice is to stay as active as you can manage rather than resting in bed — prolonged rest slows recovery. The medicine is there to make movement bearable, not to replace it.
It relieves symptoms rather than treating a cause. Persistent or recurrent back pain needs assessment.
How Spasmend fits into this medicine category
| Group | Examples | What it does |
|---|---|---|
| Simple analgesics | Paracetamol (Donapan) | Pain and fever; minimal anti-inflammatory effect |
| Muscle relaxant + analgesic | Spasmend, Norflex Co, Lenaspasm | Painful muscle spasm |
| Centrally acting muscle relaxants | Mephenesin, methocarbamol, orphenadrine | Reduce spasm; sedating |
| NSAIDs | Ibuprofen, naproxen | Pain and inflammation |
| Compound analgesics | Napacod, Stilpane | Paracetamol with codeine |
| Corticosteroids | Prednisone | Powerful anti-inflammatory, as courses |
An anti-inflammatory is often used alongside this for back pain, since it works by a different mechanism — but check first, and never add more paracetamol. See the pain, inflammation and musculoskeletal medicines hub.
What to check before using Spasmend
Check everything else you take for paracetamol. This is the most important practical point. Paracetamol appears in a great many cold and flu remedies, sinus products and painkillers, and taking one alongside Spasmend means taking paracetamol twice — the most common route to serious accidental overdose.
Do not drive or operate machinery until you know how it affects you. Mephenesin causes drowsiness.
Do not drink alcohol with it. Alcohol adds to the drowsiness and increases the risk of liver harm from paracetamol.
Speak to a pharmacist or doctor first if you:
- Have liver disease, or drink alcohol heavily — relevant to the paracetamol.
- Have kidney disease.
- Weigh under 50 kg, which reduces the maximum safe paracetamol amount.
- Are malnourished, eating very little, or significantly underweight — this genuinely lowers the threshold for liver harm.
- Have myasthenia gravis, or another neuromuscular condition.
- Have epilepsy.
- Are elderly, where drowsiness, dizziness and falls matter more.
- Are pregnant or breastfeeding.
- Are giving it to a child, which generally requires medical advice.
- Take warfarin.
- Take any other sedating medicine — opioids, benzodiazepines, sleeping tablets or sedating antihistamines.
Follow the pack instructions and do not exceed the stated maximum in 24 hours. This page does not set doses.
Possible cautions and when to ask a pharmacist or doctor
Common effects are drowsiness, dizziness, light-headedness, nausea and weakness.
Stop and seek medical attention if you develop:
- Marked drowsiness, or difficulty rousing, particularly with alcohol or another sedative.
- Confusion, especially in an older person.
- A fall, or repeated unsteadiness.
- Swelling of the face, lips or tongue, or difficulty breathing.
- A rash, blistering or peeling skin.
- Yellowing of the eyes or skin.
- Fever, sore throat or mouth ulcers, or unusual bruising or bleeding.
- Worsening weakness, if you have myasthenia gravis.
Paracetamol overdose is a medical emergency and does not feel like one at first. Someone who has taken too much may feel entirely well for a day or more while liver damage develops silently. If you think too much has been taken — even accidentally, even if the person seems fine — go to an emergency department immediately with the packaging. The antidote works best given early.
See a doctor rather than continuing if:
- Pain lasts more than a week or two, or worsens.
- You have numbness, tingling or weakness in a limb.
- You have loss of bladder or bowel control, or numbness around the groin — seek emergency care immediately.
- Back pain follows significant injury or a fall.
- Pain comes with fever, unintended weight loss or night sweats.
- Pain wakes you at night, or is worse lying down.
- You are over 50 with new back pain, or have a history of cancer or osteoporosis.
- You need it repeatedly for recurrent episodes — recurrent back pain often responds better to physiotherapy and exercise than to medicine.
Related medicine guides
- Browse Pain, Inflammation & Musculoskeletal Medicines guides
- Read: Prednisone used for
- Read: Donapan used for
Frequently asked questions
What is Spasmend used for? Painful muscle spasm — acute back and neck pain, stiff neck, and muscular pain after strain. Each tablet contains paracetamol 500 mg with mephenesin 150 mg.
Is Spasmend a muscle relaxant? Partly. The mephenesin is a centrally acting muscle relaxant; the paracetamol relieves pain. Together they interrupt the pain–spasm cycle.
Does it make you drowsy? Yes, often. Do not drive or operate machinery until you know how it affects you.
Can I take paracetamol with it? No. It already contains paracetamol, and adding more risks overdose. Check cold and flu remedies too.
Can I take ibuprofen with it? Usually yes, as they work differently, but check with a pharmacist. What you must avoid is extra paracetamol.
How long can I take it? Short-term — a few days to a couple of weeks. Muscle relaxants work best in the acute phase.
Should I rest my back? Staying as active as you can manage generally speeds recovery. Prolonged bed rest slows it.
Can I drink alcohol with it? No. Alcohol adds to the drowsiness and increases the risk of liver harm from the paracetamol.