Laxatone and Cat Lax are lubricants, not true laxatives. They are helpful in getting things like hairballs through the gastrointestinal system, but don't help much with constipation.
If it's been two days since he passed a stool but he is still eating and seems fine we may be able to help him.
But if he stops eating, starts vomiting or is constantly in the box straining then he will need a veterinary visit and probably an enema to get him right.
If this is something that happens repeatedly we need to figure out why it is happening and start measures to avoid it.
If he's an older guy with hip or spinal arthritis that make it hurt to get into position or has nerves that aren't properly functioning due to arthritic changes compressing spinal nerves we can help with inflammation and arthritis symptoms with a glucosamine/chondroitin supplement (like Cosequin) and an omega 3 fatty acid supplement like 3 V Caps or Derm Caps. In some cases using a nonsteroidal anti-inflammatory or pain medication like Gabapentin for very short bursts of time may help as well.
You can also try feeding canned only food, and adding tuna juice or sardine juice or low salt chicken broth to her food to get more fluids in. Many of these kitties would benefit from eating a canned senior food that is higher in fiber. The fiber helps improve gastrointestinal motility and canned food is simply higher in fluids.
Another option is adding a tablespoon of canned pumpkin (not pie filling, just pumpkin) to his current canned food once or twice daily. Some cats like the taste and will eat it directly or sometimes mixing it with canned kitten food gets them to eat it. The combination of increased moisture and fiber is very helpful for many cats.
Another option to soften stools is Miralax, 1/8th to 1/4 of a teaspoon once or twice daily to soften stools to start. You can mix this with some canned food or baby food. Start with a low dose and increase it if you must. Make sure to push fluids when using Miralax as it works by drawing fluids into the gastrointestinal tract and can lead to dehydration if we don't increase fluid intake.
Most adult cats are lactose intolerant, so giving him 1/4 cup of milk to drink may help as it can work as a mild laxative.
If he has any sort of early organ disease, primarily kidney failure, that can cause drier, more difficult to pass stools. An examination, bloodwork and urinalysis will help diagnose this and guide treatment, but certainly increasing fluid intake is a great start.
If adding fluids and canned pumpkin or Miralax aren't enough long term then he may need medication from his veterinarian.
If he isn't eating and/or has vomited I recommend that he be seen promptly as that may indicate obstipation, which is severe constipation with very large, impossible to pass stools that must be broken down manually under sedation.
We may also need to use a medication called lactulose chronically to keep stools soft and easy to pass, and sometimes we may need to add a medication to stimulate colonic motility, for example Cisapride.
There are two options for feeding a cat with chronic constipation if that becomes the case for him. One is to increase fiber as a stimulant to get the colon moving. I mentioned increasing fiber in his diet earlier in my write up, and that's what we usually start with. The other option is feeding a highly digestible diet so very little stool is produced and there is less to move through the colon. Sometimes it takes trial and error to see which one will work for your kitty. Whichever one you use make sure to feed canned food, add water or low salt chicken broth to improve his hydration and offer plenty of water to drink. Perhaps a kitty water fountain will encourage him to drink more.
Hills i/d is a low residue diet designed to produce little stool. Hills r/d or w/d are both high fiber foods to stimulate colonic motility. If he responds well to fiber but doesn't like those foods you can use 1/8th of a teaspoon of Miralax or Pumpkin, as I mentioned previously, added to his food as well to keep stools soft.
Some cats with chronic constipation can get a condition called megacolon, where the colon loses its propulsive, muscular function and stools sit in it becoming large, dry and difficult to pass. In those cases we try diet manipulation (usually low residue diets work best), and we must use drugs like cisapride to improve motility as well as lactulose to soften stools. If the colon simply isn't working though these cats will need surgery to remove the diseased portion of the colon. They usually do quite well after surgery.
Best of luck with your fellow, please let me know if you have any further questions.